WATERFOWL AND WETLANDS AN INTEGRATED REVIEW
Edited by Theodore A. Bookhout
. ~ , , WATERFOWL AND WETLANDS AN INTEGRATED REVIEW
Proceedings of a symposium
held at the 39th Midwest Fish and Wildlife Conference Madison, Wisconsin 5 Decem ber 1977
Sponsored by the North Central Section The Wildlife Society
Edited by Theodore A. Bookhout 1979
, Printed by La Crosse Printing Co., Inc. La Crosse, Wisconsin 54601 PREFACE
This volume resulted from a Symposium entitled "Waterfowl and Wetlands An Integrated Review" held 5 December 1977 at the 39th Midwest Fish and Wildlife Conference, Madison, Wisconsin. This Symposium was sponsored by the North Central Section of The Wildlife Society. Financial assistance for publication was provided by the U.S. Fish and Wild life Service, Mississippi Flyway Council, and Mr. Robert Winthrop. Twelve papers were presented during the Symposium that attempted to summarize our current state of knowledge about dabbling ducks and their habitat needs and pref erences throughout the year. The adaptive strategies of dabbling ducks and the implications for management were the common theme of the papers. The Symposium was organized by Leigh H. Fredrickson and Harold H. Prince. Theodore A. Bookhout accepted the editorial responsibilities and David D. Kennedy directed the fund raising aspects. We express our sincere appreciation to all who have made this volume possible. Special thanks go to the many individuals who served as peer reviewers. They were: C. David Ankney, Dale H. Arner, I. Joseph Ball, Calvin Barstow, James C. Bartonek, David A. Culver, Robert B. Dahlgren, David S. Gilmer, John P.'Kelsall, Gregory Lie, Harry G. Lumsden, Sheldon I. Lustick, Frank McKin ney, Harvey Miller, Aaron Moen, Nolan G. Perret, Lonnie D. Schroeder, and Joseph Shapiro. FOREWORD
Management of our waterfowl resource has become both more difficult and more necessary. The driving force behind this reality is the continued development of resources and space on our continent and a "fresh water crisis" looming beyond the "energy crisis" (Wetzel 1978). Our knowledge of dabbling ducks and their habitat needs has expanded con siderably from the classic studies of breeding biology and migration. This is a time when the studies of breeding biology for dabbling ducks can be summarized and future research questions expanded to be more inclusive. Previous wetland related symposia have not only provided a summary of informa tion, but have served as an important research stimulus for students and biologists. The proceedings from the species-specific symposia on wood ducks in 1964 (Trefethen 1966) and on Canada geese (Hine and Schoenfeld 1968) in 1967. both sponsored by the North Central Section of The Wildlife Society. had a wide distribution. and copies of the original printing are nearly impossible to acquire. Although these efforts are cited extensively. the Saskatoon Wetlands Seminar (1969) provided a more integrated approach to wetland problems and served a wider audience. Changes in research techniques and new developments in ecological thinking have influenced the direction. interpretation, and application of waterfowl research since the previous symposia were published. Fretwell's (1972)findings that suggest winter is a period of prime importance to survival emphasize the need for a greater under standing of anatid biology between nesting cycles. The efforts of the Northern Prairie Wildlife Research Center indicate new approaches to food habits and feeding studies are essential. The stimulus for energetics work has come from Ricklefs (1974) and King (1972, 1974), and the importance of understanding behavioral responses in rela tion to habitats has been emphasized by McKinney (1972). The broad generalizations of seasonal use of trophic levels provided by Weller (1975) serve as a base for exciting research. The collection of papers in this volume is an attempt to provide examples of current thinking and techniques now used by waterfowl experts. The goal of this symposium was to provide a new stimulus for students and others that reflect a new direction for this exciting field - waterfowl and wetlands.
LITERATURE CITED
FRETWELL, S. D. 1972. Populations in a seasonal environment. Princeton University Press, Princeton, NJ. 217pp. HINE. R. L., AND C. SCHOENFELD, eds. 1968. Canada goose management. Dembar Educa tional Research Services, Inc., Madison, WI. 195pp. KING, J. R. 1972. Energetics of reproduction in birds. Pages 78-120 in D. S. Farner, ed. Breed ing biology of birds. National Academy of Sciences, Washington, D.C. __ . 1974. Seasonal allocation of time and energy resources in birds. Pages 4-70 in R. A. Paynter, Jr., ed. Avian energetics. Nuttall Ornitho!. Club Pub\. 15. McKINNEY, F. 1972. Ecoethological aspects of reproduction. Pages 6-21 in D. S. Farner, ed. Breeding biology of birds. National Academy of Sciences, Washington, D.C. RICKLEFS, R. E. 1974. Energetics of reproduction in birds. Pages 151-292in R. A. Paynter, Jr., ed. Avian energetics. Nuttall Ornithol. Club Pub!. 15. SASKATOON WETLANDS SEMINAR. 1969. Can. Wild\. ServoRep. Ser. 6.262pp. TREFETHEN, J. B., ed. 1966. Wood duck management and research: a symposium. Wildlife Management Institute, Washington, D.C. 212pp. WELLER, M. W. 1975. Migratory waterfowl: a hemispheric perspective. Pub!. Bio!. Inst. Inv. Cient., V.A.N.L., Mexico 1:8,9-130. WETZEL, R. G. 1978. Foreword and introduction. Pages xiii-xvii in R. E. Good, D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands. Academic Press, New York.
ii CONTENTS
SPECIES DISTRIBUTION, HABITATS, AND CHARACTERISTICS OF BREEDING DABBLING DUCKS IN NORTH AMERICA Frank C. Bellrose ...... 1
NITROGEN AND PHOSPHORUS DYNAMICS IN INLAND FRESHWATER WETLANDS John A. Kadlec , .. , , , .. , . , , . , . , , . , , , , .. , .. 17
SPATIAL AND TEMPORAL HABITAT RELATIONSHIPS OF BREEDING DABBLING DUCKS IN PRAIRIE WETLANDS (Abstract only) David L. Trauger and Jerome H. Stoudt , .. 43
SOCIAL INTERACTIONS AND SP ACING BEHAVIOR IN BREEDING DABBLING DUCKS (Abstract only) Scott R. Derrickson , , , .. , .. , .. , . , . . .. 45
FOODS OF LAYING FEMALE DABBLING DUCKS ON THE BREEDING GROUNDS George A. Swanson, Gary L. Krapu, and Jerome R. Serie ... , . , .... , ..... " 47
NUTRITION OF FEMALE DABBLING DUCKS DURING REPRODUCTION Gary 1. Krapu ... , .... , ... , . , ..... , , ... , . . . .. , ...... 59
BIOENERGETICS OF BREEDING DABBLING DUCKS R. B. Owen, Jr. and K. J. Reinecke...... , , . , ... ,. 71
INDIVIDUAL VARIATION AND THE ANALYSIS OF MALLARD POPULATIONS Bruce D. J. Batt , . , .. , .. , , , . , .. , ...... 95
BIOENERGETICS OF POSTBREEDING DABBLING DUCKS Harold H. Prince...... , , . , , . , ...... , , . 103
HABITAT UTILIZATION BY POSTBREEDING WATERFOWL Leigh H. Fredrickson and Ronald D. Drobney , , , . , , . , 119
WINTER HABITAT OF DABBLING DUCKS - PHYSICAL, CHEMICAL, AND BIOLOGICAL ASPECTS Robert H. Chabreck .. , . , .. , , , . , , , , , . , , 133
SYMPOSIUM SUMMARY AND COMMENTS ON THE FUTURE OF WATERFOWL John P. Rogers , , . , . , , , , , . , 143
iii WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Syrnp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Pu blished in 1979
SPECIES DISTRIBUTION, HABITATS, AND CHARACTERISTICS OF BREEDING DABBLING DUCKS IN NORTH AMERICA
FRANK C. BELLROSE
lliinois Natural History Survey, Havana, Dlinois 62644
Abstract: The abundance and distribution of breeding dabbling duck species vary tremendously in the several landscape forms that extend from north central United States to the Arctic. With in this extensive part of the continent, the northern prairies, including their subclimax park lands, have the largest number of breeding dabblers. Pond abundance within the several prairie associations does not affect all species of dabbling ducks to the same extent. Mallards (Anus platyrhynchos) appear to be the least tolerant of the crowding that develops where pond densi ties are lowest. Mallards predominate as breeders in all landscape forms except the tundra and open taiga of Alaska and Canada, regions where both the pintail (A. acuta) and the American wigeon (A. americana) are more abundant. The abundance of ponds in the Prairie Pothole Region is the most important single factor regulating the production of mallards and no doubt other dabbling species. Management strategies should consider the effect of pond density upon both the abundance of breeding ducks and the production of young. Temperature, precipitation, and evaporation have both a direct and an indirect effect on the breeding distribution and abun dance of the several species of dabbling ducks. These factors determine the ultimate plant associations and they also have a proximate influence on the breeding abundance of waterfowl.
Various species of dabbling ducks exploitation of wetland habitats, dab breed over the entire North American bling species aggregate about 61% of all continent, occupying a diversity of wet breeding ducks. In contrast, diving ducks land types. They have a broader breeding form only 17% and sea ducks 22% of range and occupy more wetland niches breeding duck populations. than do diving ducks. Only in the tundra The disparity between dabblers and and open taiga are breeding diving ducks divers is even more pronounced in the more abundant than breeding dabblers. harvest. Dabbling ducks comprised 86% South of the tundra and open taiga, dab of hunters' bags in the United States bling ducks outnumber divers. Because during 1961-70 and diving ducks 14% of their greater adaptability in the (Carney et al. 1975). Because of their BREEDING DABBLING DUCKS IN NORTH AMERICA
abundance and importance to the hunter, further analyzed for this report. it is appropriate to conduct a symposium devoted to identification of habitat AREA OF LANDSCAPEFORM requirements, population dynamics, and research and management needs of dab The principal breeding grounds of bling ducks. dabblers extend in an arc from north This report examines the principal central Nebraska and southeastern plant associations occupied by breeding South Dakota to the Yukon Delta, Alaska. dabblers and explores some of the rea Within this arc the landscape form sons for the diverse patterns in their changes thusly from southeast to north distribution. Analyses are focused on the west: tall grass prairie, mixed prairie, important plant associations extending parkland, closed taiga, subarctic deltas, from the central United States to the open taiga, arctic deltas, and tundra. Arctic Ocean that are occupied by more West of the mixed prairie lies the short than two species of dabblers. grass prairie, an important adjunct to I am indebted to a number of people the prairie breeding grounds. Still for contributing to the quality of this farther west are the valleys and basins of paper: R. Pospahala, U.S. Fish and Wild the Rocky Mountains, which contain life Service, for the breeding ground important wetlands for breeding water data; V. Wright, TIlinois Department of fowl. Because this discussion concerns Conservation, for statistical guidance; biomes (tundra), plant associations (tall D. Trauger, U.S. Fish and Wildlife Ser grass prairie), and physiographic areas vice, for information on breeding habi (mountain valleys), I use the term tats; G. Sanderson, H. Schultz, and H. landscape form to encompass all three Henderson, TIlinois Natural History Sur types. vey, for editorial suggestions. Table 1 shows the approximate num DERIVATION OF DATA ber of square miles of each landscape form used by breeding dabbling ducks. The bulk of the data used in these Because of similar plant communities, analyses was provided by R. Pospahala, Old Crow Flats is included with the U.S. Fish and Wildlife Service. They Mackenzie River delta, and the Slave were derived from the annual aerial River parklands with the Athabasca surveys of the important waterfowl delta. The eastern closed taiga embraces breeding grounds in North America as Ontario and Quebec. described by Hanson and Hawkins The tundra east of the Boreal Forest in (1974). The transects flown on these sur Canada harbors few breeding dabbling veys and their delineation into 50 dif ducks. Because of their limited numbers, ferent strata are shown in Bellrose (1976) it lies outside the area surveyed annually and Benning et al. (1978). Strata isolate for breeding waterfowl. This vast region a particular physiographic unit of the covers about 900,000 mi 2, 465,000 of breeding grounds that provides func which are on the mainland. Sparsely tional means of statistical analysis. In distributed pintails, perhaps as many as formation on the breeding population of 75,000, breed in the eastern tundra where ducks in the Intermountain Region was they are the only important dabbling supplied by state and provincial water ducks. But the tundra is highly impor fowl biologists. These data were initially tant to sea ducks and geese, the majority supplied to assist me in preparing of which breed within its confines. material for use in Ducks, Geese, and The renowned Prairie Pothole Region Swans ofNorth. America (Bellrose 1976). in its traditional definition embraces the This material has been recast and climax mixed prairie and the subclimax
2 Table 1. Population density (ducks/ mi2) of various species of dabbling ducks among landscape forms of North America, 1955-74.a Square Black G.w. B. w. and % of total dabblers Landscape form miles Mallard duck Wigeon Gadwall teal Pintail C. teal Shoveler Av. ::E > Alaskan tundra 48,300 1.18 1.78 0.01 1.14 12.24 0.01 0.21 16.57 2.43 >-3 Alaskan open taiga 14,900 3.62 6.84 4.03 6.44 1.21 22.15 1.00 trJ b ;:0 Canadian open taiga 187,500 1.11 1.31 tr 0.56 1.68 tr 0.03 4.69 2.67 "i Combined open taigaC 202,400 1.29 1.72 tr 0.81 2.03 tr 0.12 5.97 3.67 0 Alaskan closed taiga 18,100 3.01 3.74 2.39 23.08 tr 0.67 32.90 1.81 :sr Northern closed taiga 422,700 4.39 0.02 1.81 0.16 2.06 1.10 1.40 0.81 11.76 15.09 > Eastern closed taiga 549,000 0.60 0.80 0.11 0.01 1.52 2.54 Z C Combined closed taiga 989,800 2.26 0.45 0.84 0.07 0.98 0.90 0.60 0.36 6.47 19.44 0 Canadian Arctic deltas 6,900 5.46 16.62 2.65 23.72 tr 0.84 49.31 1.03 ::E w trJ Subarctic deltas 20,170 17.21 7.27 1.05 6.06 6.30 5.21 2.79 45.88 2.81 >-3 89,458 7.59 4.41 3.77 11.96 16.72 5.59 77.96 21.17 r Parklands 27.92 > Mixed prairie 143,124 15.34 3.91 5.22 1.62 15.05 16.85 5.71 63.71 27.68 Z Shortgrass prairie 145,369 6.76 2.46 1.36 0.82 5.40 3.13 1.40 21.34 9.42 0 Tallgrass prairie 82,151 3.32 1.10 0.11 1.64 7.30 1.18 14.66 3.66 tr: tr: Combined prairii 460,102 12.93 3.47 3.11 1.52 9.01 10.78 3.52 44.33 61.93 --< Great Lakes forest 194,000 2.04 0.50 0.15 0.21 0.07 1.84 0.02 4.83 2.84 ~ '1j Intermountain valleys 5.84 0 Total 1,921,672 100.00 atr: aData from the U.S. Fish and Wildlife Service and from state waterfowl biologists. ~ bTrace.
CSubtotal~,; not included in final total. BREEDING DABBLING DUCKS IN NORTH AMERICA
parklands that cover 232,582 mi 2, 12% of I have been unable to obtain data on the waterfowl breeding areas listed in the area of valleys and basins amid the Table 1. In a vegetative sense the Prairie ranges of the western mountains. Per- Pothole Region also includes the tall- sonnel of the map library at the Uni grass and shortgrass prairie associations, versity of Illinois diligently searched aggregating 460,102 mi 2, or 24% of all the their references but were unable to locate plant communities appraised. I use the data on the surface area of either the broader coverage in this paper. The rem- mountain ranges or the valleys and nant tallgrass prairie area available to basins. Therefore, I could not appraise breeding waterfowl lies in western Min- the number of breeding ducks per square nesota, the easternmost counties of the mile in the intermountain valleys. Dakotas, and the Sandhills of Nebraska. Counts of water areas in the Prairie Because wetlands become much reduced Pothole Region are made in May and west of the Missouri River in the Dako- July, concurrently with the appraisal of tas, this region has been placed in the breeding waterfowl populations and shortgrass prairie association along with • their production. The distribution and Montana, the southwest corner of abundance of May ponds have been sum- Saskatchewan (stratum 33) and the marized by stratum and landscape form southern tenth of Alberta (stratum 29). in Table 2. Table 2. The distribution of small wetlands by stratum and landscapeform in the northern prairies of North America, 1955-77. Square No. Landscapeform Stratum miles ponds No.ponds/mi 2 Parklands 26 26,448 440,700 16.7 30 18,570 240,050 12.9 31 21,086 441,000 20.9 34 13,164 482,830 36.7 38 5,654 42,300 7.5 40 4,536 162,830 35.9 Total!average 89,458 1,809,710 20.2 Mixed prairie 27 11,274 135,500 11.6 28 12,890 95,050 7.5 32 37,912 463,670 12.2 35 9,044 302,630 33.5 39 6,552 164,510 25.1 45 26,625 335,500 12.6 46 14,238 129,800 9.1 48 24,589 147,590 6.0 Total!average 143,124 1,774,250 12.4 Shortgrass prairie 29 13,235 85,700 6.5 33 11,345 95,740 8.4 41 32,902 113,640 3.5 42 40,758 107,940 2.7 43 19,835 92,700 4.7 44 27,298 100,660 3.7 Total!average 145,369 596,380 4.1 Tallgrass prairie W.Minnesota 36,500 127,750 3.5 N. Dakota 47 7,821 24,500 3.1 S. Dakota 49 15,830 74,410 4.7 N. Nebraska 22,000 170,940 7.8 Total!average 82,151 397,600 4.8
4 WATERFOWL AND WETLANDS SYMPOSIUM
The abundance and density of water other landscape forms still fewer. areas vary greatly with stratum and Another way of evaluating the impor vegetation type (Table 2). As might be tance of waterfowl habitats is to assess expected, the lowest density of ponds the density of dabbling ducks using them. occurred in the semi-arid shortgrass This assessment shows that all the grass prairie association. Compared to it there land associations support a density of were 1.2 times as many ponds per square 44/mi 2 with slightly higher densities of mile in tallgrass prairie, 3 times as many 49 and 46/mi 2, respectively, in the Arctic in mixed prairie, and 4.9 times as many delta and su barctic areas. Fertile waters in the relatively well-watered parklands. and balanced interspersion between land and water in northern deltas probably IMPORTANCE OF LANDSCAPE account for the unusual density of breed FORM TO DUCKS ing ducks at such high latitudes. Lowest In my appraisal of the breeding distri densities occur in the Great Lakes forest bution of dabbling ducks, 32,396,105 are association, the Canadian open taiga, and accounted for (Table 1). The largest the northern closed taiga (Table 1). proportion of these birds, 27.7%, inhabits Compared with similar plant associa the mixed prairie, followed by 21.2% in tions in Canada, Alaska has greater the adjacent parklands, 9.4% in the concentrations of breeding dabblers. For shortgrass prairie, and 3.7% in the tall example, the open taiga in Alaska aver grass prairie wetlands. Thus, in the ages 22.2 dabblers/rni-'; that in Canada traditional definition, the prairie pothole averages 4.7/mi 2. The closed taiga in area is occupied by 41% of the popula Alaska supports 32.9 dabbling ducks/ tion, but, including all grassland associa mi 2, the northern closed taiga in Canada tions, it is used by 62% of the breeding 11.8/mi2. The coastal tundra of Alaska dabblers. has 16.6 dabblers/mi 2 compared with Because of its vastness, the Canadian probably less than O.I/mi 2in Canada. closed taiga, west of central Ontario. A comparison of the composition of supports 15.1% of the breeding dabblers. dabbling ducks in the various landscape Intermountain valleys contain 5.8%, the forms reveals species differences (Table Great Lakes forest region 2.8%, and 3). Pintails predominate through all of Table3. The percentage distribution of various dabbling ducks breeding in a variety of landscapeforms in North America, 1955-77. Black G.w. B. w. & Landscapeform Mallard duck Wigeon Gadwall teal Pintail C. teal Shoveler Alaskan tundra 7.1 10.7 0.1 6.9 73.8 0.1 1.3 Alaskan opentaiga 16.4 30.9 18.2 29.1 5.5 Canadian opentaiga 23.7 27.9 tra 11.8 35.9 tr 0.6 Alaskan closedtaiga 9.2 11.4 7.3 70.2 tr 2.1 Northern closedtaiga 37.4 0.2 15.4 1.4 17.5 9.4 11.9 6.9 Eastern closedtaiga 39.4 52.5 7.2 1.0 Canadian Arcticdeltas 11.1 33.7 5.4 48.1 tr 1.7 Subarcticdeltas 37.5 15.9 2.3 13.2 13.7 11.4 6.1 Parklands 35.8 9.7 5.7 4.8 15.3 21.4 7.2 Mixed prairie 24.1 6.1 8.2 2.5 23.6 26.4 9.0 Shortgrass prairie 31.7 11.5 6.4 3.9 25.3 14.7 6.6 Tallgrass prairie 22.7 7.5 0.8 11.2 49.8 8.1 Great Lakesforest 42.3 10.5 3.1 4.4 1.4 38.0 0.4 Intermountainvalleys 49.4 6.2 9.7 2.9 7.7 20.1 3.9 aTrace.
5 BREEDING DABBLING DUCKS IN NORTH AMERICA
the Arctic habitats as far south as the 70 G, W, TEAL Canadian closed taiga. That part of the dabbling duck population composed of 58 ARCTIC DELTA pintails amounts to 74% on the Alaskan 55 tundra and declines through Alaskan 5~ OPEN TAIGA open and closed taiga to 9% in the Cana dian closed taiga. It is apparent that 52 ~ SUBARCTI C DELTAS pintails prefer the more open tundra and ~ 50 '"e open taiga to wetlands in the closed taiga. '5 58 In the Arctic, wigeons rank next to ~ = 55 ~ CLOSED TAIGA pintails in abundance. Immediately to =~ = ~ the south, in the Canadian subarctic 5~ '" deltas and in the northern closed taiga, 52 they occur in slightly greater numbers PARKLAND than the pintail. They also occur in 50 slightly greater numbers in the Alaskan ~8 MIXED PRAIRIE open taiga (Table 1). Wetlands with some ~5 wooded vegetation influence mallards TALLGRASS PRAIRIE more than other dabblers; they rank ~~ highest in the closed taiga, subarctic 20 15 10 10 15 20 deltas, prairie parkland, Great Lakes NUMBER PER SQUARE MILE forest, and intermountain valleys. In this respect, American green-winged teals Fig. 1. The latitudinal breeding population (Anas crecca) are more like mallards distribution of blue-winged and green-winged than pintails, but green wings are like teals in the various landscape forms, 1955-74. pintails in being more Arctic-oriented. The latitudinal change in abundance the tallgrass prairie or in wetlands of the between blue-winged (A. discors) and Great Lakes forest. green-winged teals along a line from Gadwalls (A. strepera) are limited in southeast South Dakota to the Mackenzie viable breeding populations to the River delta is shown in Fig. 1. It is ap prairies and the intermountain valleys. parent that blue-winged teals have the In comparison with other dabblers, their greatest affinity for prairie pothole density is the greatest in wetlands of the habitats, whereas green-winged teals intermountain valleys and the mixed and are related to the habitats of the sub tallgrass prairie areas. Only in these arctic and Arctic regions. landscapes do gadwalls outnumber their Cinnamon teals (A. cuanoptera) occur close competitors, wigeons. almost exclusively in the intermountain Three species of dabblers predominate valleys, where they have been eminently in the all-important Prairie Pothole more successful than have blue-winged Region: mallards, blue-winged teals, and teals. In prairie pothole habitats, the pintails. They are of about equal abun blue-winged teal complex is second only dance on the potholes of the mixed to mallards in abundance (Table 1). prairie, but mallards overwhelm the Northern shovelers (A. clypeata) have others, particularly pintails, in the park exploited most of the areas north of the lands. parklands and su barctic deltas to a Although several dabbling duck greater degree than have blue-winged species breed in the eastern closed taiga teals, but they have not been as success east of Manitoba, only mallards and ful as blue-winged teals in wetlands of black ducks (A. rubripes) have been emi
6 WATERFOWL AND WETLANDS SYMPOSIUM
nently successful (Table 3). These 2 3.1 in the tallgrass prairie. The relatively species together compose 92% of the low number of ducks in parkland ponds dabblers utilizing this extensive region. is partly due to the larger number of Mallards appear to decline in abundance ponds. from west to east, and, conversely, black Among dabbling ducks associated with ducks increase from west to east. grasslands, the parklands contain the Of the waterfowl breeding in the Pre greatest density of these species: mal cam brian Sh ield of eastern Ontario, lards, wigeons, and green-winged teals. Dennis (1974:55) reported that 23% were The mixed prairie has the greatest den black ducks and 7% were mallards (32 sities of gad walls, blue-winged teals, and 10%, respectively, of dabbling shovelers, and pintails. Although no species). The closed taiga in the clay belt, species is more abundant in either the north of the Precambrian Shield, con shortgrass or tallgrass prairie associa tained a greater abundance of ducks. tions, there are more mallards, wigeons, There, black ducks composed 17% and and pintails per pond in shortgrass mallards 15% of breeding waterfowl (30 prairie strata. and 23%, respectively, of dabbling species). In the open taiga of the Ungava Pond Density and Duck Density Peninsula, Quebec, Gillespie and Wet more (1974:147) found that black ducks Figure 2 demonstrates the effect of the composed about 80% of the- dabbling density of ponds on their occupancy by ducks and 25% of all ducks. dabbling ducks. The formula, Duck den During the last decade, there has been sity= a + b log pond density, gives a growing evidence that the mallard has better fit (higher R2) than the simple increased in the western range of the linear regression when data from all the black duck at the expense of the black strata in the Prairie Pothole Region are duck. Laperle (1974:18) believes that this used. However, when plant associations change is not solely because the mallard within the prairie region are separated, is a better competitor but also because it the relationship is more complex. Within is more adaptable to man's degradation the tallgrass prairie no relationship of habitats. exists between the density of ponds and ducks, whereas within the shortgrass PRAIRIE POTHOLE REGION prairie the relationship is linear. This fit is best because when pond density is The Prairie Pothole Region warrants relatively low (as in the shortgrass further analysis because of its impor prairie), numbers of ducks and ponds tance to breeding dabbling ducks. Table 4 increase together. But the logarithmic shows that the density of dabbling ducks fit demonstrates that where ponds are varies among the several grassland asso already numerous, the density of dab ciations as follows: parklands 78/mi2, bling ducks increases progressively more mixed prairie 64/mi2, shortgrass prairie slowly than the density of ponds. This 21/mi2, and tallgrassprairie 15/mi2. The trend is especially apparent in the parklands have more water areas, 20/ Prairie Pothole Region and in its park mi 2, than the other grassland associa land association; where pond density tions which have: mixed prairie 12/mj2, exceeds 12/mi2, duck density increases shortgrass 4/mi2, and tallgrass 5/mi2. slide progressively further behind On the basis of the number of ducks per increases in pond density. At levels up to pond, there are 5.5 in shortgrass prairie, 12 ponds/ml/, dabbling ducks are most 5.1 in mixed prairie, 3.9 in parklands, and abundant in mixed prairie strata, least
7 Table 4. The relationship of dabbling ducks to various breeding ground habitats in the Prairie Region of North America, 1955-74. Landscape form Mallard b Gadwall Wigeon G. w. teal B. w. teal Shoveler Pintail All dabblers and stratum SMa PP SM PP SM PP SM PP SM PP SM PP SM PP SM PP Parklands 26 33.8 2.0 6.8 0.4 8.7 0.5 5.6 0.3 16.2 1.0 6.5 0.4 12.2 0.7 89.8 5.4 30 25.2 2.0 4.2 0.3 8.8 0.7 3.5 0.3 11.4 0.9 5.3 0.4 12.3 1.0 70.6 5.5 31 28.0 1.3 3.3 0.2 8.4 0.4 2.7 0.1 13.4 0.6 6.3 0.3 14.7 0.7 76.8 3.7 34 34.1 0.9 3.4 0.1 6.4 0.2 3.4 0.1 25.6 0.7 4.6 0.1 11.0 0.3 88.5 2.4 38 3.5 0.5 0.3 tr " 0.5 0.5 0.6 0.1 5.4 0.7 5.2 0.7 2.9 0.4 18.3 2.8 ttl 40 26.9 0.8 4.8 tr 6.8 0.2 4.4 0.1 36.7 1.0 5.7 0.2 9.2 0.3 94.5 2.5 ~ trl Total!average 27.9 1.4 4.4 0.2 7.6 0.4 3.8 0.2 16.7 0.8 5.6 0.3 12.0 0.6 78.0 3.9 trl t:I Mixed prairie 52 27 22.4 1.9 5.1 0.4 7.8 0.7 2.5 0.2 10.4 0.9 7.7 0.7 20.4 1.8 55.8 6.6 0 28 14.4 1.9 3.4 0.5 5.3 0.7 1.4 0.2 5.3 0.7 5.7 0.8 25.7 3.4 61.1 8.1 t:I 6.0 > 32 20.6 1.7 5.3 0.4 7.1 0.6 2.5 0.2 11.1 0.9 6.2 0.5 20.1 1.6 72.9 ttl 35 20.2 0.6 3.9 0.1 3.9 0.1 3.7 0.1 25.1 0.8 5.2 0.2 14.1 0.4 76.0 2.3 ttl r 39 11.7 0.5 3.3 0.1 3.1 0.1 3.1 0.1 31.2 1.2 4.4 0.2 7.5 0.3 64.4 2.6 52 45 10.6 0.8 5.7 0.5 1.4 0.1 0.6 0.1 15.7 1.3 5.0 0.4 10.9 0.9 49.8 4.0 0 46 8.3 0.9 7.3 0.8 8.6 0.9 0.5 0.1 21.7 2.4 5.0 0.6 9.2 1.0 60.7 6.7 t:I 00 48 7.2 1.2 4.4 0.7 0.4 0.1 0.5 0.1 19.1 3.2 4.1 0.7 7.4 1.2 43.1 7.2 ~ Total!average 15.3 1.2 5.2 0.4 3.9 0.3 1.6 0.1 16.9 1.4 5.7 0.5 15.1 1.2 63.7 5.1 a ~ Shortgrass prairie tr: 29 12.7 2.0 1.8 0.3 3.7 0.6 0.8 0.1 2.5 0.4 3.0 0.5 15.6 2.4 40.0 6.2 -Z 33 13.5 1.6 3.0 0.4 5.0 0.6 1.5 0.2 6.2 0.7 4.1 0.5 16.0 1.9 49.3 5.8 Z 0 41 7.9 2.3 2.5 0.7 3.9 1.1 1.1 0.3 3.0 0.9 1.8 0.5 7.4 2.1 27.5 8.0 ~ 42 4.5 1.7 0.6 0.2 1.6 0.6 0.9 0.6 1.3 0.5 0.5 0.2 1.1 0.4 10.4 4.2 '"'3 43 3.5 0.8 0.4 0.1 1.0 0.2 0.6 0.1 2.3 0.5 0.8 0.2 2.5 0.5 11.1 2.4 :r:: > 44 5.5 1.5 1.0 0.3 1.6 0.4 0.3 0.1 4.9 1.3 0.9 0.2 2.1 0.6 16.3 4.4 s::: Total!average 6.8 1.7 1.4 0.4 2.5 0.6 0.8 0.2 3.0 0.8 1.2 0.3 5.4 1.4 21.3 5.5 trl ~ Tallgrass prairie -a W. Minnesota 3.0 0.9 3.4 1.0 0.8 tr 0.1 0.3 7.3 2.2 > 47 2.5 0.9 4.5 1.7 0.2 0.1 0.1 0.1 2.8 1.1 0.9 0.3 1.4 0.5 12.4 4.6 49 4.3 0.9 1.0 0.2 0.3 0.1 tr 0.1 12.0 2.6 2.1 0.4 2.3 0.5 22.0 4.7 Sandhills 3.6 0.5 1.0 0.1 0.1 tr 6.7 0.9 1.6 0.2 1.7 0.2 15.0 1.9 Total!average 3.3 0.7 1.1 0.2 0.1 tr 0.1 tr 7.3 1.5 1.2 0.2 1.6 0.3 14.8 3.1 a Ducks/mi. bDucks/pond. cTrace. WATERFOWL AND WETLANDS SYMPOSIUM
120 = PRAIRIE POTHOLE REGION 0.79 R2 2 -- = PARKLANDS 0.73 R 2 w • • = MIXED PRAIRIE 0.46 R -.J 105 2 :IE: o 0 = SHORTGRASS PRAIRIE 0.76 R w 0::: c:J; 90 --- ::::> Cll - V) 0::: w 75 0 V) ~ u 60 ::::> /' t=l / u.. 0 45 / 0::: w /
9 BREEDING DABBLING DUCKS IN NORTH AMERICA
2 9 A A = PARKLANDS R 0.32 ~ = MIXED PRAIRIE R2 0.81 8 o • • SHORTGRASS PRAIRIE (NOT SIG.)
co 7 z 0 0... c::: UJ 6 0...
5 10 15 20 25 30 35 40 NUMBER OF PONDS PER SQUARE MILE Fig. 3. The number of prairie ponds per square mile compared with the number of dabbling ducks per pond among strata grouped according to park lands or mixed prairie association, 1955 74. less crowding than do other dabbling rate in the shortgrass and mixed prairie ducks. Both mallards (Pospahala et al. associations than in the parklands and 1974) and pintails (Smith 1970) are tallgrass associations. These findings known to overfly the Prairie Pothole suggest that breeding pintails prefer the Region in those years that May ponds more open grasslands, and that they decline in number. They appear in tolerate greater densities than do mal greater numbers in the areas to the north lards. Moreover, other species of dab on lakes of the open and closed taiga and blers are more tolerant of crowding on subarctic deltas. My'data suggest that prairie ponds. Therefore, they do not other dabbling ducks do not overfly the overfly the Prairie Pothole Region as prairies to the extent that these two spe often as do mallards and pintails. cies do. Mallards and pintails are both early Pond Abundance and Mallard nesting ducks and nest in similar habi Production tats in the Prairie Pothole Region. Because they appear as potential com The relationship between (1) the size of petitors, I examined the effect of reduc the continental mallard breeding popula tion in pond density on the comparative tion and the abundance of ponds in the abundance of mallards and pintails (Fig. Prairie Pothole Region and (2) a pre 5). Linear regressions indicate that the dicted production of young is shown in density of pintails increases at a higher Fig. 6. A multiple regression equation,
10 WATERFOWL AND WETLANDS SYMPOSIUM
E.5
'"= 5.0 5.0 '='~ 2=0.76 5,5 ---- = MIXED PRAIRIE R = ~ / ~ 4.5 - - - - = sHORTGRAss PRAIRIE R2=0.49 V> ~ 2=0.78 ~ 5. D ------= PARKLAND R = '" 4.0 ----- = TALLGRA,' PRAIRIE R2=0.72 ~ z z 4.5 ""0 0 ~ I = 4, D ex: 3.5
D 0.5 1.0 1.5 2,0 2.5 3,0 a 0.5 1,0 1.5 2.0 2.5 3,0 3.5 NUMBER OF MALLARDS PER POND NUMBER OF MALLARDS PER POND Fig. 4. The relationship between the number of mallards per prairie pond and the number Fig. 5. The relationship between the number of other dabbling ducks per pond among the of mallards per prairie pond and the number several strata in each of four prairie associa of pintails per pond among the several strata tions,1955-74. ineachoffour prairie associations. 1955-74. Number of young mallards in the fall and the num ber of May ponds in the population = -0.04 log + 0.58 log May grassland associations alone account for breeding numbers + 0.49 log May ponds, 60% of the annual variability in the fall was significant with an R 2 of 0.61. It is numbers of young mallards. Hence, the evident that both the size of the mallard contribution of young mallards - or the population returning to the breeding lack of it - from this region produces grounds and the spring abundance of pronounced variations in the fall popula prairie ponds are important factors tion in spite of the production of young governing the size of the fall continental from over 40% of the mallards that breed population. Although the number of elsewhere. The contribution to the fall predicted young rises as the number of population from wetlands of the taiga May ponds increases. it rises at a de and subarctic and Arctic deltas should creasing rate. remain quite similar year in and year out It is important to realize that from because of stable habitat conditions. 1955 to 1976 about 42% of the mallards Actually. potential production might be bred outside the Prairie Pothole Region. expected to increase during drought Yet the production of young from the years because the mallard overflight of prairies is such an important component the prairies adds to the ind igenous of the fall population that its size greatly population. Therefore, it is apparent influences the entire continental popula that, through the period of analysis, the tion. The coefficient of determination 40% of the mallards breeding outside the (Fig. 6) implies that breeding numbers prairies contributed fewer than 40% of
11 BREEDING DABBLING DUCKS IN NORTH AMERICA
14,000 c
D 13,000
(/) 0 12,000 z c::e (/) E a::=J ::I: lLOOO ~ z 10,000 <.!> F Z ::=Ja >- 9,000 l.La 0::: LU a:::l 8,000 :E ::=J Z G A= 7,500 ,000 PONDS 7,000 B= 6,500 ,000 PONDS C= 5,500 ,000 PONDS 6,000 0= 4,500, 000 PONDS E= 3,500 ,000 PONDS 5,000 F= 2,500,000 PONDS G= 1,500,000 PONDS
5,000 7,000 9,000 6,000 8,000 10,000 12,000 14,000 NUMBER OF BREEDING DUCKS IN THOUSANDS Fig. 6. The predictive influence of mallard breeding numbers and the abundance of May ponds in the Prairie Pothole Region on the number of young in the fall continental population. The analysis is based upon a multiple regression and common logarithmic transformation of the basic data. the young to the continental population. ability to a variety of breeding habitats If it were otherwise, the prairies would and climates. In relation to other species, not exert such a marked influence on the it achieves its greatest degree of success yearly status of mallards. The adage, "As in the parklands. -' the prairies go, so go the game ducks," is Conversely, among the dabbling ducks, a supportable truism. black ducks and cinnamon teals have the most restricted breeding ranges over the DISCUSSION part of North America considered in this report. The traits that enabled black Their mode of flight and their feeding ducks and cinnamon teals to occupy habits have enabled dabbling ducks to restricted ranges more advantageously utilize a greater range and diversity of than the closely related mallards and habitats than do other waterfowl. blue-winged teals are not well under Among dabbling ducks, the ubiquitous stood. Although in recent years mallards mallard exhibits the greatest adapt appear to be invading the western part
12 WATERFOWL AND WETLANDS SYMPOSIUM
of the black duck's breeding range, black nest earlier than gadwalls and green ducks still sustain the most viable popu winged teals earlier than bluewings lation over their ancestral range. The (Bellrose 1976). The ability of wigeons black duck's breeding range is charac and greenwings to breed earlier than terized by a high precipitation-low evapo their relatives may account for their ration ratio. Where this ratio is the greater abundance in the North. highest, the black duck appears to be the Perhaps greenwings have minimized most successful at thwarting the en competition with bluewings through croachment of the mallard. their greater adaptation to habitats in a The cinnamon teal's breeding range is harsher climatic region. Otherwise, it conversely characterized by a low preci might be expected that green-winged pitation-high evaporation ratio. This teal teals would be proportionately more reaches its greatest breeding abundance abundant in the highly productive in the Great Salt Lake basin, Utah, fol Prairie Pothole Region. A similar rela lowed by the Malheur basin, Oregon, tionship appears to apply to the wigeon areas that have the lowest precipitation gadwall distribution. Wigeons predomi evaporation ratios (Bellrose 1976). It is in nate north of the Prairie Pothole Region, these and other similar areas that the but both wigeons and gad walls are about cinnamon teal has been most successful equally numerous in the prairies (Fig. 6). at limiting the encroachment of the blue Mallards do not populate Arctic wing. For example, Wheeler (1965) habitats to the extent that pintails do. reported that the blue-winged teal has Although mallards and pintails vie as the expanded its range and numbers in earliest nesters among the dabblers, northeastern California. Thus, certain mallards are probably less able to breed climatic conditions appear to be the fun successfully under the more ad verse damental reason that black ducks and conditions in the Arctic. However, a cinnamon teals have not been over study of mallard and pintail egg produc whelmed by sympatric species that are tion in the parklands and the Arctic by more numerous and occupy larger Calverley and Boag (1977) does not fully ranges. substantiate this premise. They found Gadwalls and blue-winged teals have that both mallards and pintails laid su bstantially lower breeding numbers fewer eggs per hen in the Arctic than in north of the Prairie Pothole Region. They the parklands. Not only were there fewer are both late-nesting species, suggesting eggs per clutch in the Arctic for both that warm temperatures are important species, but there was also a significantly to their nesting activities. Therefore, larger proportion of nonlaying females. temperatures prevailing during the short The reduction in egg productivity was summer in the Arctic and su barctic similar for both species. But egg produc appear to be proximate factors respon tion is only one factor in the number of sible for limiting tlie northward ex young produced, and, in the Arctic, pin pansion of gad walls and blue-winged tails may be more successful than mal teals. lards in nesting and brood rearing. Both the southern-breeding gadwall The greater concentration of almost all and the blue-winged teal have closely species of dabbling ducks in similar related species, the wigeon and the landscape forms in Alaska than in green-winged teal, that manage to main Canada appears to be related to habitat tain substantial breeding populations and summer climate. There is a much farther north in the Arctic and subarctic. better interspersion between small water In similar geographic locations, wigeons areas and land in the tundra and taiga of
13 BREEDING DABBLING DUCKS IN NORTH AMERICA
Alaska than in similar landscape forms Temperature, precipitation, and in Canada. The better interspersion of evaporation are weather factors that small water areas in Alaska stems in influence the distribution of breeding part from the terrain - the large areas dabbling ducks. These factors have an of flat or gently sloping plains along the ultimate influence in determining plant coast and between the mountain ranges associations and, within the vegetation in interior Alaska. Moreover, at similar framework, a proximate influence on the latitudes, the weather is more moderate breeding birds themselves. in Alaska because of the influence of the The tapering off in the abundance of Japanese Current on the Bering Sea. breeding dabbling ducks where ponds The Arctic Slope of Alaska contains exceed 12/mi2 (Fig. 2) has application to about 12,000,000mi 2 of tundra wetlands the strategies of acquisition and manage that appear to be excellent for breeding ment of wetlands in the Prairie Pothole waterfowl. Yet, except for perhaps as Region. This region makes an enormous many as 20,000 pintails, few other dab contribution to the status of the fall con bling ducks occur there, apparently tinental population of mallards. Both the because of the short Bummer and harsh returnmg number of mallards to the weather. Moreover, most of the pintails breeding grounds and the number of May that do occur there are nonbreeders, for ponds on the prairies have important Eldridge and Derksen (1977, paper pre roles in determining the production of sented at 39th Midwest Fish and Wildlife young (Fig. 6). Here, too, management Conference, Madison, WI) found little strategy should consider the saturation evidence of pintails breeding on the effect of pond density in the production Arctic Slope. of young.
14 WATERFOWL AND WETLANDS SYMPOSIUM
LITERATURE CITED
BELLROSE, F. C. 1976. Ducks, geese and GILLESPIE, D. 1., AND S. P. WETMORE. swans of North America. Stackpole 1974. Waterfowl surveys in Labrador Books, Harrisburg, PA. 543pp. Ungava, 1970, 1971, 1972. Pages 8-18 in H. Boyd, ed. Waterfowl studies. Can. BENNING, D. S., S. L. RHOADES, 1. D. Wild\. Servo Rep. Ser. 29. SCHROEDER, AND M. M. SMITH. 1978. Waterfowl status report, 1974. U.S. Fish HANSON, R. C., AND A. S. HAWKINS. 1974. Wild\. Servo Spec. Sci. Rep. Wildl. 211. Counting ducks and duck-ponds in prairie 98pp. Canada: how and why. Naturalist 25(4): 8-11. CALVERLEY, B. K., AND D. A. BOAG. 1977. LAPERLE, M. 1974. Effects of water level Reproductive potential in parkland - and fluctuations on duck breeding success. arctic-nesting populations of mallards Pages 18-30 in H. Boyd, ed. Waterfowl and pintails (Anatidae). Can. J. Zoo\. studies. Can. Wild\. Servo Rep. Ser. 29. 55(8):1242-1251. POSPAHALA, R. S., D. R. ANDERSON, AND C. J. HENNY. 1974. Population CARNEY, S. M., M. F. SORENSEN, AND ecology of the mallard. II. Breeding E. M. MARTIN. 1975. Distribution in habitat conditions, size of breeding popu states and counties of waterfowl species lations, and production indices. Bur. harvested during the 1961-70 hunting Sport Fish. Wild\. Resour. Pub\. 115. seasons. U.S. Fish Wild\. Servo Spec. Sci. 73pp. Rep. Wild\. 187. 132pp. SMITH, R. I. 1970. Response of pintail breed DENNIS, D. G. 1974. Waterfowl observations ing populations to drought. J. Wild\. during the nesting season in Precambrian Manage. 34(4):943-946. and clay belt areas of north-central WHEELER, R. J. 1965. Pioneer of the blue On tario. Pages 53-56 in H. Boyd. ed. winged teal in California, Oregon, Wash Waterfowl studies. Can. Wild\. Servo Rep. ington, and British Columbia. Murrelet Ser.29. 46(1):40-42.
15
WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977 Symp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
NITROGEN AND PHOSPHORUS DYNAMICS IN INLAND FRESHWATER WETLANDS
JOHN A. KADLEC
Department of Wildlife Science, Utah State University, Logan, Utah 84322
Abstract: Few studies have covered even a majority of the important aspects of the biogeo chemical cycles of Nand P in freshwater wetland ecosystems. Available information is 'nostly on amounts present at some point in time in various ecosystem components, such as plants, soils, or water. The amounts vary with time and site, and reported values are influenced by methodology. For sediments, in particular, most current methods are inadequate to give mean ingful information about nutrient supplies. Standing crops (g/m2) of Nand P are the product of concentration and total plant biomass. Emergents generally have higher standing crop bio mass and hence contain more Nand P. Processes important in understanding the dynamics of Nand P in wetland ecosystems include: water flows into and out of the wetland, rainfall, evapo transpiration, nitrogen fixation, denitrification, animal movements, plant uptake, translocation, decomposition, leaching, animal ingestion and excretion, and a variety of chemical processes. Plants take up nutrients from both sediments and water, and nutrient movements both upward and downward through plants have been demonstrated. Evidence is accumulating that, for submersed and floating-leaved species and even some emergents, the net movement is upward, and substantial quantities of P, and probably N, are moved from the sediments through the plant to the water. Animals are usually considered to be a minor influence on Nand P cycles, but occasionally large local concentrations of waterfowl may have detectable effects, particularly on N dynamics. Dense growths of aquatic and marsh plants may require amounts of Nand P in excess of the amount present, in available form, at anyone time. Therefore the rates at which these nutrients are supplied, cycled internally, and removed from the wetland ecosystem are critical to plant growth. Either or both Nand P may be limiting in many marshes. Management practicesshouldbe aimedat enhancingsupply rates and internal recycling rates whilereducing loss rates. Inputs and outputs are mostly via water for P; gaseous exchange is also of major importance for N. Controlling P means careful attention to hydrology, especially during periods when P is mobile. Denitrification is clearly enhanced by rapid and frequent water level fluctua tions, which leads to the speculation that N may be conserved by careful water level regulation.
]7 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
The information on nutrient dynamics cularly in the United States. Neverthe in inland freshwater wetlands is largely less, much of what is known in limnology from fragmented and diverse sources. can be applied, with care, to wetlands. Relatively few studies have covered a Some wetlands have little or no surface majority of the important aspects of a water most of the time, and the relevant nutrient cycle in such an ecosystem. literature is then often in agriculture and Similarly, the num her of elements, in soils. Particularly rich sources of infor their various forms, that have been con mation for such systems are studies of sidered is usually only a part of those lowland rice culture and work on peat that a text in plant physiology would list lands, particularly in Russia. as nutrients. Perhaps most commonly The conceptual framework used in considered are nitrogen (N) and phospho reviewing Nand P cycles in wetlands is rus (P), possibly because they are limit the mass balance approach. Simply ing nutrients in many situations. This stated, this says that the change in paper will deal primarily with those two amount of N or P in the wetland (or any elements. subdivision thereof) at any point or inter Because studies and data are scarce, I val of time is a function of the difference shall discuss a variety of wetland types, between inputs and outputs. We are excluding from major consideration only therefore mostly interested in how much the extensive information on tidal salt N or P comes in or goes out per unit of marshes. The use of the term "fresh time. Quantities present are of interest water" in the title will pose little dif primarily in determining changes in stor ficulty, for few studies of nutrient cycles ages - how much more or less is present have been done in interior saline wet at one time compared to another. lands. The dynamics of nutrient relationships ANNUAL BUDGETS are the major emphasis of this discus sion, largely because this leads to a Annual budgets show the balance of better understanding of wetlands and, I imports and exports of Nand P as well believe, the potential for better manage as the changes in internal storage within ment. No effort has been made to sum the wetland. Examples of such budgets marize all available data on the nutrient are rare because of the difficulty in content of vegetation, or standing crops, Obtaining all the required data. In the but rather only general levels are indi following sections, I will discuss first the cated. Processes by which nutrients are paths of Nand P movement into and out made available to vascular plants will be of wetlands, then some quantitative data emphasized with the view that these are on the rates of Nand P movement, and of fundamental importance in determin finally look at a few examples of budgets. ing the character of marshes for water fowl. A rich marsh or poor marsh is characterized basically by the vegetation, Nutrient Import and E%port which in turn is intimately related to a number of factors, including processes Nitrogen and phosphorus enter and that supply or remove nutrients from leave wetlands in or with water and in the plants. animal biomass; in addition, N move Wetlands for waterfowl are basically ments include transfers to and from the shallow bodies of water and should fall gas phase in the atmosphere. Water within the general purview of the discip additions occur from groundwater (e.g., line of limnology. However, limnologists springs and seeps), rain, and surface have not done much in wetlands, parti runoff. The volume of water input and
13 WATERFOWL AND WETLANDS SYMPOSIUM
the concentration of the various ions mostly by groundwater, and yet other must be known to calculate the total marshes are only sheltered parts of amount of, say, Nand P being added to rivers. Given all this variation, know- the wetland by those routes. Both ledge of the local hydrology is vital to an groundwater and surface runoff may understanding of the marsh ecosystem enter by channels (i.e., streams and and its management or preservation. Yet rivers). Chemistry of groundwater is pro- there are not many thorough hydrologic foundly influenced by geology, surface studies of wetlands or marshes. water by soils and land use practices, In general, there are two critical and rainfall by atmospheric dust and hydrologic parameters for wetland eco pollutants (Likens 1975). Outputs or systems. The first is water depth and its losses may be via streams, to ground- seasonal variation, about which much is water, or to evaporation and transpira- known (e.g., Kadlec 1960, Harris and tion. Evaporation losses increase ion Marshall 1963,Meeks 1969, Burgess 1969, concentration and are critical in saline, Weller 1978). The second vital parameter brackish, and alkali wetlands in interior is the flow, flushing, or turnover rate. and western North America, as well as The importance of water turnover rate elsewhere around the world. has been hinted at in a few wetland These various processes in the hydrol- studies (Cook and Powers 1958, Kadlec ogy of marshes vary greatly in their 1960, Andersen 1974), but it is now con- importance in different wetland types. sidered a key parameter in some models Virtually the only inputs and outputs of of the trophic dynamics of lakes (e.g., some bogs are rainfall and evapotranspi- Dillon and Rigler 1974).Turnover rate as ration, whereas some potholes are fed well as depth, and their seasonal varia- Table 1. Estimated "average" quantities of Nand P (g/m2/yr) from various sources (from Likens 1975). Source N P Rainfall 0.80 0.030 Forested area 0.25 0.008 Pastured area 0.85 0.017 Cultivated cropland 0.75 0.440 Citrus farms 2.20 0.018 Muck farms 0.11 0.140 Urban area 0.80 0.350 Feedlot runoff 80 30 Domestic sewage 3,900a 800a Septic tanks Immediate 2,400b 140b Remote 970b 14b Domestic ducks 480 c 90 c aGrams per capita per year. b Grams per septic tank per year. c Grams per duck per year.
19 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
Table 2. Nitrogen and phosphorus inputs (kg/ha/yr) to wetlands by way of precipitation. Source Total P Likens (1975), U.S. and Canada 6.6-10 0.04-0.35
Crisp (1966), England 8.2 0.69
Richardson et al. (1978J, Great Lakes Region 5.2 0.30
Ulehlova et al. (1973), Czechoslovakia 8 0.60 tions, depend on the dynamic balance There is some potential for gain or between the inputs and outputs of water loss of Nand P from marshes by move discussed earlier. Depending on the ments of animals or by harvest of marsh chemical composition and particulate vegetation. Waterfowl or marsh bird loads of the incoming and outgoing excreta are potentially the source of large water, the fertility of the wetland can be amounts of Nand P (Likens 1975 - see markedly affected. Table 1, Davies 1973, McColl and Burger Likens (1975) reviewed the literature 1976). Waterfowl sometimes consume a on quantities of Nand P likely to be significant fraction of the production of brought to a water body from various macrophytes (Anderson and Low 1976). sources (Table 1). Phosphorus and Crisp (1966) estimated that invertebrate ammonium-N are relatively easily drift and sheep grazing removed 1.7 mg immobilized in contact with soils, so that P/m2/ yr and 11.0 mg N/m2/ yr from a contributions from most land uses are Pen nine moorland, which is relatively not large unless the drainage area is minor - probably less than measure large. Sewage, feedlots, and domestic ment error on some other inputs and out ducks are high Nand P producers, and puts. On the other hand, Vallentyne substantial inputs from any of these (1952) estimated 0.15 mg P/m 2/ day and sources can lead to enrichment. Some 2.26 mg N/m 21day left a lake surface in further data on nutrient inputs via rain the biomass of emerging insects, mostly fall, usually including some "dry fall" or midges (Tendipedidae), which could be dust, are given in Table 2. Total inputs significant if most of those insects left (loading) of Nand P per unit area of the marsh and were not replaced by marsh are highly variable, depending on immigrants. the relative proportions of various land Among the major nutrients, C, 0, and uses and sources of Nand P in the catch N can enter and leave wetlands as gases. ment. The role of CO2 and 02 in photosynthesis Reliable data on the quantities and and respiration need not be elaborated nutrient content of a ground water flow here. Molecular N enters or leaves water ing into wetlands are very difficult to or sediments by diffusion, but the critical obtain. Yet, in some marshes, ground processes adding to or subtracting from water may be a large part of the annual the internal N cycle are N fixation and water supply. and thus presumably also denitrification. the annual supply of some nutrients. Nitrogen fixation occurs through Local geology often has a significant microbial and algal action, including impact on both the quantity and quality symbiotic associations of microorga of ground water. So little is known of nisms and higher plants. Blue-green this complex system that it must be con algae are well known as N fixers (Evans sidered a major research need. 'and Barber 1977) and are common in
20 WATERFOWL AND WETLANDS SYMPOSIUM
wetlands (Kasischke 1974). Symbiotic N to be sites of high denitrification. Well fixation is known in alder (Alnus spp.) oxygenated waters of riverine or lake and sweet gale (Myrica ,gale) (Moore and shore marshes over highly mineral soils Bellamy 1974). Nitrogen fixation by probably exhibit much less denitrifica microorganisms associated with peat or tion activity. organic marsh soils has been shown by Denitrification loss rates apparently many studies (Moore and Bellamy 1974). vary widely. Andersen (1974) estimated Conversely, N may be limiting for plant that 0-54% of the annual N input to 6 growth in saline, brackish, or alkaline shallow Danish lakes was lost through interior marshes (Moreau 1976) as it is in denitrification. Keeney et al. (1971) esti the near coastal marine environment mated 63% of the N entering Lake Men (Ryther and Dunstan 1971). dota, Wisconsin, in seepage waters was Data from lakes (Likens 1975) suggest lost through denitrification. Other a range of N fixation from 0.04 to 4.56 estimates for lakes, as summarized by g N/m2/yr, with most values less than Likens (1975), range from 0.008 mg NIl/ 1 g N/m2/yr. Marshes rich in blue-green day to 300 mg N/1/day. The available algae and bacteria, and per haps gen information suggests that the middle of erally warmer than lakes, may support that range, a few mg/1/day, is a reason somewhat higher rates. Evans and Bar able first approximation. If the marsh ber (1977) cite rates ranging from about averages about 1 m deep, this loss would 0.6 g/m 2/yr for microorganisms asso be of the same order, but perhaps exceed ciated with Typha to 6.0 g/m2/yr for the input by N fixation. This agrees with microorganisms associated with Glyceria Vollenweider's (1968) conclusion that borealis. denitrification "normally" exceeds fixa Denitrification, the conversion of N03 tion in lakes. N to N2, possibly through intermediate compounds, has been found in many Examples of Annual Budgets marshes. The process is mostly microbial and requires an anaerobic environment Recently, Carpenter and Adams (1977) (Patrick et al. 1976). Rates of 2-4 ppm/ summarized the annual imports, exports, day for soils and water from southern and net change of Nand P for Lake marshes and swamps have been demon Wingra in Madison, Wisconsin (Table 3). strated in the laboratory (Patrick et al. The net annual gains of both Nand P 1976). Frequent (order of days) intermit were in excess of the peak standing crops tent flooding and drying accelerate the of Nand P in Myriophyllum biomass. loss (Reddy and Patrick 1976). There is Two relevant studies have been done on some evidence that this is potentially a ecosystems related to, but somewhat major pathway in N cycling in many different from, those in interior North marshes (Kadlec 1976, Patrick and America. Andersen (1974) dealt with six Reddy 1976). The amount of N loss is shallow Danish lakes (see Table 4) and related to the close proximity of an Crisp (1966) studied an eroding peat bog aerobic zone in which nitrification can in England. Andersen found a liberation proceed to N03 and an anaerobic zone in of P from the sediment in some lakes in which the N03 is converted to N2. The summer and deposition in other seasons. process also requires an energy source Some of his shallower lakes, with shorter for the microorganisms, usually in the water turnover times, showed more P form of carbon from organic matter. As being exported than imported, although a result, shallow waters with fluctua Kvind so, Kal so, and Halle so showed tions and organic substrates are likely reversals; that is, they were net import
21 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
Table 3. Input-output Nand P balances (kg/ha) for a hard water eutrophic lake, Lake Wingra, in Madison, Wisconsin (modified from Carpenter and Adams 1977). N P Annual imports Precipitation 8.14 0.24 Surface runoff 49.64 10.71 Springs 39.86 0.71 Groundwater 10.93 0 Dry fallout 15.29 0.79 Total import 123.86 12.45 Annual exports Outlet discharge 17.71 1.03 Groundwater 1.79 0.05 Total export 19.50 1.08 Annual net balance +104.36 + 11.37 Maximum standing crop of Nand P in Myriophyllum spicatum 19.29 4.14 ers of P one year and net exporters of P amount of the N output was as N2. Crisp in either the preceding or following year. (1966) showed net export of Nand P, All of Andersen's lakes exported less N mostly in the form of erosion loss of peat than they imported and a substantial particulates. A study of nutrient budgets
Table 4. Annual balances of Nand P (g/m 2/yr) from some shallow water ecosystems in Europe.
Retention Input Output a Net storage Mean depth time Kind of area (m) (days I Year N P N P N P Shallow Dan ish lakes b Bryrup Lang 5.0 130 1972 845 3.92 37.7 1.88 46.8 2.04 1973 80.5 3.08 36.0 1.77 44.5 1.31 Kvind S0 1.9 14 1972 175.0 16.50 117.9 10.84 57.1 5.66 1973 149.3 11.40 117.2 16.22 32.1 -4.82 Kuls0 2.2 18 1972 110.6 9.06 90.0 9.88 20.6 -0.82 1973 107.1 13.18 78.3 12.56 28.8 0.62
Salten lang SOl 4.1 59 1972 26.4 3.92 21.6 1.85 4.8 2.07 1973 23.8 3.18 16.8 1.36 7.0 1.82 Halle S0 ca. 2.8 ca. 38 1972 86.3 2.63 39.4 2.91 46.9 -0.28 1973 85.3 2.19 40.9 2.05 44.4 -0.14 St igsholrn 50 ca. 1.2 ca. 11 1972 80.4 4.48 62.3 5.19 18.1 -0.71 1973 81.9 3.26 61.2 4.01 20.7 -0.75 Eroding peat bogC Total 0.82 0.046-0.069 1.77 0.086 -0.95 -0.017 to -0.040 Total less erosional loss 0.31 0.041 +0.51 +0.005 to + 0.028
a Nitrogen output includes 0-50% denitrification. b Data from Andersen (1974). C Data from Crisp (1966).
22 WATERFOWL AND WETLANDS SYMPOSIUM
Table 5. Concentrations of Nand P (mg/liter) in water flowing into and out of shallow water eco systems. Inputs Outputs Source TDP N03-N NH4-N TDP N03-N NH4-N Klopatek 0.17-2.40 0.07-2.03 0.10-2.61 0.10-0.50 0.10-0.68a 0.13-1.59a (1975) 0.02-0.03 0.17-2.16 0.07-1.69 0.04-0.69 0.03-1.51 0.03-5.81 Kitchens et al. 0.095-0.393b 0.125-0.300 0.015-0.250 0.075-0.1oob 0.075-0.300 0.020-0.130 (1975) Lee et al. 0.Q1-0.55 b 0.10-1.93 0.00-2.1 (1975) aHigh values following drainage. bOr tho-P0 4.
for the Okefenokee Swamp (RykieI1977), One of the chief difficulties in studying although not dealing with Nor P, showed the overall nutrient budgets of marshes a mixed pattern of net imports for Ca is that excellent information on hydro and K, and net losses for Mg, Na, and Cl. logy and nutrient concentration is
Table 6. Nitrogen and phosphorus contents of tissue of vascular aquatic plants from selected studies. Percent Source Species N P Boyd (1978) 27 wetland 2.2G±0.14 a 35 wetland 0.25±0.02 submersed (6 sp) 2.56 0.20 floating- leaved (4 sp) 2.56 0.23 emergent (8 sp) 1.42 0.19 Potamogeton dioersifolius 2.86 0.27 Kvet(1975) Typha latifolia 1.5-2.0 0.10-0.15 Kvet (1973) Phragmites communis 1.12b_5.lOc 0.084 -0.240c
Richardson et al. (1978) Cluimaedaphme c calyculata 1.71-2.59 0.09-0.22c Brinson and Davis (1976) Nuphcr luteumd 1.65e-5.7 C 0.48 Bernatowicz (1969) 19species 1.18-2.82 0.01-0.61 aSE. bS tems. cLeaves. d% ash-free dry wt. eRhizome.
23 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
required. Lee et al. (1975:108) put it this tissue (Table 6). Even here, the under way: ground parts of such plants are not com "We hoped it would be possible monly sampled. Two excellent sum to make quantitative estimates of maries of available data and the vari the effect of marshes on water ability of nutrient concentration in plant quality, in particular, to be able to tissues in time, space, plant part, and make mass-balance computations kinds of plants are available (Boyd 1978, on the amount of chemicals trans Prentki et al. 1978) and will not be re ported through the marsh from peated here. Although variations are various sources, the transforma common, Boyd's (1978) means of 0.25% P tions that take place in the marsh, and 2.26% N, oven-dry weight basis, are and the amount that is transported good first approximations. Data on out of it. This was not possible standing crops of Nand P (Table 7) are because of the extremely complex more variable than concentrations hydrology of the marsh system." because of the additional variability in In fact, even Crisp's study (1966) suffers standing crop biomass of aquatic and from an inability to deal adequately with marsh plants. Indeed, Boyd and Hess nutrient inputs from ground water and (1970)showed a high correlation between stream flow over bedrock; and it is con standing crop biomass of cattail (Typha latifolia) and g/m2 of P (r =0.69) and sidered one of the better studies. Several investigators have looked at N (r=0.76). On the whole, however, stands of emergent vegetation contain the concentrations of nutrients in inflow 2 2 ing and outflowing, or only outflowing, 2-4 g P/m and 20-40 g N/m , except in water (Table 5). However, in the absence peatlands containing Cladium jamai cense and Carex spp, (Table 7). Sub of data on the volume of water flowing per unit of time, such data cannot be mersed and floating-leaved species evaluated in terms of the amounts of usually have lower biomass per square nutrients being supplied to or removed meter (e.g., Boyd 1971b), and conse from the marsh, either seasonally or quently the standing crop of Nand P in annually. areas of submersed vegetation is lower, even though the percentage of Nand P may be higher. Reasonable first approxi NUTRIENT CYCLES mations of standing crops in f1oating WITHIN WETLANDS leaved and submersed species are 10-20 g N/m2 and 1-2 g P/m2. Amounts of Nand P in Wetland Variation in the ash content of aquatic Components plants can markedly affect reported nutrient concentrations, depending on The storages of Nand P in various whether the basis for calculation is ash parts of marsh ecosystems vary substan free dry weight or simply dry weight. tially, as does information about them. Kollman and Wali (1976)reported 35.4 to The amount of Nand P in plants, ani 56% ash content of total dry weight for mals, soils, and water is a function of Potamogeton pectinatus, Kvet (1973)6% both the concentration and the quantity for Phragmites communis, Boyd and of material containing that concentra Hess (1970) 1-6% for Typha latifolia, and tion. Data on concentration are more Boyd (1978) 6.1-40.6% for 40 species of common than data on amounts. Perhaps wetland plants. Obviously, subtracting the best data available are those for con as much as 40-50%of the total dry weight centrations of Nand P in vascular plant to correct for ash content can about
24 WATERFOWL AND WETLANDS SYMPOSIUM
Table 7. Aboveground standing crops (g/m 2 ) of Nand P in vascular aquatic plants as reported in selected studies. Source Species N P Klopatek (1975) mixed emergents 16.9 3.7 Kvet (1975) Typha laiifolia (maximum) 25.1 1.6 Dykyjova and Hradecka (1973) Phragmites communis 28-46 3-4 Ulehlova et al. (1973) Phraqmites communis 23.44 3.67 Kvet (1973) Phriurmites communis 18.8-34.7 1.06-2.67 Boyd (1967) Charaspp. 27.6 2.8 Myriophyllum spp. 9.3 0.9 Ceratophyllum spp. 16.7 1.3 Steward and Ornes (1975) Cladium jtimaicenee 5.5-8.9 0.25 Boyd (1971b) Justicia americana 44.3 2.8 (maximum observed) Boyd(1971a) Typha laiifolia 5-12 0.7-1.8
Wentz (1976) Carex spp. 4-6 0.2-0.4 Brinson and Davis (1976) Nuphar luteum 0.197 double reported percentages of mineral sediments can exist in two phases: dis nutrients. Careful attention is needed, sol ved in interstitial waters. or asso but either approach should give the same ciated with (or in) the solid sediment standing crop of nutrients. Ash content particles. The solid phase can include: is usually highest in submersed species, 1) nutrient ions adsorbed on mineral or average 21%. next highest in floating organic particles, often called exchange leaved species, average 16'1(" and lowest able; 2) oxides, hydroxides, and hydrous in emergent species, average 12% (Brin oxides. together with coprecipitated ions; son and Davis 1976). 3) nutrients bound in organic matter; Poor analytic technique can also 4) nutrients bound with sulfides (mostly contribute tc error in reported nutrient metals); and 5) chemicals bound within concentrations. For example. neglect of the crystalline lattice of sediment calcium carbonate encrustations that particles (Brannon et al. 1976). Few form on underwater plant parts in hard studies have carefully distinguished (high bicarbonate) waters can bias dry among these forms of nutrients in sedi weight determinations. ments. More importantly, it is not at all The P, N, and other nutrients found in clear in what forms Nand P are available
25 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
Table 8. Nitrogen and phosphorus content of wetland sediments.
N P Source Sediment type Total Exchangeable (ppm) Total Exchange (%) N03-N NH4-N (%) able (ppm) Klopatek (1975) ca. 40% organic 1.75 0.005-0.02 3 Ulehlova et al. sand-clayb 0.18 (1973) organic sapropel b 0.53 Schroder (1975) marl 0.01-0.05 Fekete 15% organic, 0.55 13.8b (1973) 30% solids 35c 24% organic, 0.25 65b 15% solids 122.5c Richardson et al. peat b 2.54 0.09 (1978) peatC 16.9 interstitial H2O 0.06 2.10 0.125 Chamie (1976) litter 1.4-1.8 0.06-0.1 Boyd and Hess various cattail soilsb 1-116 (1970) Brinson and biologically Davis (1976) availablsd 378 Steward and peat b 0.017-0.046 0.5-24 Ornes (1975)
Kadlec various b 0-37.5 0.25-8.13 (1960) interstitial H2O 0.04-36.2 e 0.008-0. 151e aBray P-2 procedure. hDried sediment. cFresh sediment. dDried and acid extraction. eTotaJ Nand P. to wetland plants. The assumption is environment (Sculthorpe 1967) and may often made that ions dissolved in in ter be able to utilize nutrients made avail stitial water and adsorbed on various able under those conditions. particles, which are dynamically related Most analyses of wetland or marsh by chemical equilibria, are representa soils (Table 8) are done by conventional tive of sediment nutrients available to agricultural techniques, which involve plants. Other phases are generally drying and grinding the sample prior to insoluble and unavailable, except that analysis. This destroys the anaerobic under the reducing conditions often prev status of the sediment, and it probably alent in marsh soils the oxides and also shifts nutrients among the phases hydroxides may dissolve, releasing those discussed. Consequently, the results of nutrients. Aquatic and marsh plant roots such tests are of dubious value (Brannon are able to function in an anaerobic et al. 1976). Even measures of "exchange
26 WATERFOWL AND WETLANDS SYMPOSIUM
able" nutrients are biased as much as seriously affected by variations in twofold (Fekete 1973 [see Table 8], extractant and technique. Table 8 also Patrick and Mahapatra 1968). Extractant includes some data on interstitial water, and extraction techniques also affect which also are highly variable in the results. Boyd (1971b) demonstrated methods used as well as in levels found. continued release of P over 25 repeated Total N in soils is usually far greater extractions of a sediment with P-free than any other pool of N within the wet water. In agriculture, a large body of land. Much of the soil N is in organic empirical data provides the basis for form and unavailable to plants except interpreting the results of a standard soil through decomposition. A reasonable test in terms of crop requirements. In approximation of total N in marsh sedi essence, the soil test is an index whose ments is 500-1,500 g/m2 (dry weight value has been proven by long experience. basis) of which about 5-15 g/m2 is con In wetlands, no such body of empirical sidered available. data and experience exists. Generally, Converting from concentrations to studies have shown only crude correla weights per unit area or volume of Nand tions between plant growth and soil and P in marsh sediments depends on some water nutrients (Fekete 1973, Steward estimate of the dry weight (the usual and Ornes 1975) and then often with total basis for concentrations) per unit area of content, rather than exchangeable. I soil in the root zone. Marsh soils vary believe that no satisfactory procedure greatly in water and organic content and for assessing the nutrient status of therefore in dry weight per unit volume. marsh soils is yet available, although Hence it is not possible to use standard several studies such as those of Fekete agricultural conversions. Only a few (1973), Brannon et al. (1976), and Rich studies are available that report amounts ardson et al. (1978) are contributions of Nand P per hectare (Table 9), and the toward that goal. results are highly variable. Generally, Available data on total P in soils (Table quantities of total Nand P in the soil are 8) suggest concentrations vary widely substantially larger than the amounts in but are commonly in the 0.01-0.02% the plants. range (dry weight basis). Fekete's (1973) Phosphorus concentrations in surface data are much higher, for no obvious waters of wetlands (Table 10) are a little reason. Exchangeable amounts (Table 8) higher than in fresh waters in general, also vary widely, but these data are which according to Cole (1975) is usually
Table 9. Nitrogen and phosphorus standing crops (kg/ha) in wetland soils. N P Source Soil Type Total Avail. Total Avail. Ulehlova et al. organic sapropel 5,830 39.6 (1973) sand-clay 2,700 37.15 Steward and Ornes peat 15,272-15,792 8-13 97-275 0.6-2.8 (1975) Schroder marl solids 1,600 (1975) 8,000
interstitial H20 0.2 Richardson et al. peat 6,830 7.5 242 4.5 (1978) interstitial H20 4.32 0.2
27 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
about 0.02 mg/l total P. Nitrate concen seasonal patterns in more detail. tration seems to be of the same order as Nitrogen and phosphorus amounts other fresh waters, but ammonium is among the consumers (e.g., insects and frequently higher. Some of the higher birds) are usually regarded as small com values in Table 10 reflect marsh drainage pared to those in plants (Boyd 1971b). and reflooding for management pur poses, or, in the case of the TDP reported Processes within the Wetland by Komarkova and Komarek (1975), fertilization to increase fish production. The processes going on within the wet Standing crops of Nand P in wetlands land can be categorized, roughly, as surface waters are in most cases not physical-chemical, microbiological, or reported, although they could easily be macrobiological. Physical-chern ical calculated if the water depths were processes include dissolution, precipita known. tion, oxidation-reduction, adsorption, ion Both sediment and surface water N exchange, leaching, and formation of and P concentrations and standing crops complexes. Factors affecting these vary seasonally, and some of the range in processes include pH, temperature, the results reported undoubtedly reflects oxygen, and kinds and sources of sedi that variation. I have ignored seasonal ments. Most of these are well treated in variations in the interest of concentrat limnology texts and will not be empha ing on general patterns. Klopatek (1975), sized in this paper. Delaune et al. (1976) Kadlec (1976), Kollman and Wali (1976), give an excellent summary for salt and Brinson and Davis (1976) discussed marshes, much of which is applicable to
Table 10. Nitrogen and phosphorus concentrations (rng/Iiter) in surface waters of wetlands. Total Total Source N TDP P Klopatek 0.10-1.68 0.13-1.59 1.52-4.16 0.10-0.E;0 0.11-0.69 (1975) Ulehlova et al. 0.44-1.13 0.27-0.79 0.64-1.04 (1973) Boyd 0.07 0.09 0.OO8 b (1970b) Komarkova and 0.001-0.37 0.16-1.36 0.01-8.90 Komarek (1975) Steward and 0.30-1.01 0.029-0.213 Ornes (1975) Richardson et al. 0.039 0.728 0.060 (1978) Kadlec 0.03-1.79a 0.004-0.062 (1960)
Bernatowicz 0,00-0.01 0.02-0.26 0.000-0.029b (1969) aHigh values followed drainage of the wetlands. bOrtho-P0 4-P.
28 WATERFOWL AND WETLANDS SYMPOSIUM
other wetlands. Microbiological pro (1974) estimated that only 0.8-1.4% of the cesses include decomposition and oxida N, and presumably P, was cycled by tion-reduction, particularly of nitrogen beaver (Castor comadensis) populations and sulfur compounds. Factors influenc at the borders of a Michigan peatland. ing microbial action include pH, carbon Rates of nutrient uptake by vascular energy sources, and oxygen supply. plants are sometimes calculated from Macrobiological activity may be divided seasonal changes in the total amount in for convenience into plant and animal. the plants. Such rates may be under Plant uptake of nutrients is essentially estimates, as are rates of biomass pro a problem in physiological ecology. Stage duction calculated in a similar manner of growth is important, as are tempera (Prentki et al. 1978, van der Valk and ture, light, competition, and ratios Davis 1978, Whigham et al. 1978). How among the available nutrients. Plants, as ever, Table 11 gives examples of reported well as animals, apparently excrete rates of P uptake regardless of method of nu trients, but we really know little of the estimation, simply because the data are factors that influence the process. Simi so few. Daily rates have not been extra larly, there is still some controversy over polated to annual rates, because there if, when, and under what circumstances are few good data on seasonal fluctua different kinds of marsh and aquatic tions in uptake. Boyd's work (1970b) plants translocate nutrients. Ingestion suggests that in temperate areas most and excretion by animals are obviously uptake of P by Typha lati/olia occurs in a functions of the number and kinds of short period of active growth, slightly animals. This in turn is a function of the preceding maximum biomass growth. In quality and quantity of habitat provided. contrast, Brinson and Davis (1976) found In many cases, the animals may be most uptake by Nuphar luteum in winter, al ly invertebrates. Lamarra (1975) found though at less than one-half the summer the rate of recycling of P per gram body rate. The data suggest 5-20 rng P!m2 weight by animals to be negatively cor must be supplied each day during peak related with body size, so smaller ani daily uptakes, primarily from sediments, mals contribute relatively more to P inflowing water, rain and dry fall, or renewal than do larger animals. Maguire decomposition. Table 11. Rates of P uptake bysomewetland vascular plants. Source Species Rate Prentki (1978) Typha latifolia 3.5g!m2!yr Klopatek(1975) Scirpu« j7uviatilis 5.3g/m2/ yr Steward and Ornes (1973) Cladiumjamaicense 0.18 g/m2!yr Gaudet (1977) Cuperus papyrus 7.8g/m2/ yr (tropics) Boyd (1970b) Typha latifolui 19.3 mg!m2/day (maximumrate) Scirpus americanus 5.3mg/m2/day (maximumrate) Richardsonet a1. (1978) Mixed fen 0.17 g/m2/ yr Brinsonand Davis (1976) Nuphar luteum (summer 9.3 mg/m2/day uptake from sediment)
29 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
Table 12. Rates of N uptake by some wetland vascular plants. Source Species Rate Boyd (1970b) Typha latifolia 162.7 mg/m2/day (maximum rate) Scirpus americanus 34.4 mg/m2/day (maximum rate) Klopatek (1975) Scirpus fluviatilis 20.75 g/m2/yr Richardson et al. (1978) Mixed fen 3.0g/m2/yr Boyd (1971a) Typha latifolia 87-279.0 mg/m2/day Kvet (1975) Typha latifolia 140.0 mg/m2/day Toetz (1973) Cerataphy llum up to 2 mg NH4-N/ g dry wt.z'hr Gaudet (1977) Cyperus papyrus 103.3g/m2/yr (tropics)
Examples of rates of N uptake are different patterns of decomposition and presented in Table 12. Many plants can nutrient release, as shown for Typha and do take up both Nand P in excess of glauca and Scirpus fluviatilis by Davis current needs, a phenomenon known as and van der Valk (1978). Decomposition "luxury" uptake (Gerloff and Krombholz is very temperature dependent, and in 1966). Hutchinson (1975), in an exhaus the tropics Gaudet (1977) estimated 84% tive review of mineral nutrients in of the P in Cyperus papyrus disappeared aquatic plants, accepts Gerloff and in 26 days. He also showed that some of Krombholz's (1966) estimate of 1.3% N the early loss of P from dead plant and 0.13% P as the critical or minimum material is simply elution; that is, it does concentration in plant tissue. Higher not involve microbial action. values, then, presumably reflect some Microbial processes important in N luxury uptake. cycling within the sediment-water-plant Phosphorus is released more rapidly system include decomposition, ammoni than nitrogen from dead plant material. fication, and nitrification. Relatively Boyd (1970a) found that about 50% of the little of the N content of plant tissue is P in cattail was lost in 20 days, whereas lost immediately after death (Boyd in the same period the decrease in bio 1970a, Gaudet 1977, Davis and van der mass was only 20%. Brinson and Davis Valk 1978). Depending on the environ (1976) estimated the time to lose one-half ment, very little change in N concentra of the original P content of Nuphar tion of plant litter may take place for luieura aboveground parts as 6 to 9 days, months (Boyd 1970a) or years (Chamie about the same as biomass. For Justicia 1976). Even in the tropics, Gaudet (1977) americana, the time for 50% loss was found a loss of 26% of the N per m2 in found to be about 13 days in summer, 26 days, but in the same period there was only about one-half the time required for a one-third loss in biomass. Nitrogen 50% loss of biomass. In contrast, Chamie enrichment of litter apparently results (1976) found very little change in P con from the inclusion of high N content centration in sedge litter over 1 year in microorganisms that conserve N more a northern peatland. Different species than carbohydrate. Nevertheless, there is within the same marsh may have very N mineralization first to NH4 (ammoni
30 WATERFOWL AND WETLANDS SYMPOSIUM
fication) and then to N03(nitrification) this route from Scirpus fluviatilis, and which accounts for some contribution of Prentki et al. (1978) estimated 50 mg inorganic N to water or soil. The conver PIm 21day from Typha latifolia. Some sion of NH4 to N03 requires oxygen that translocation back to roots also occurs at may not be available for extended the end of the growing season. Klopatek periods of time in marsh sediments. Thus (1975) estimated that movement as it is not uncommon to observe accumula 0.44 g PIm2/yr in S. fluviatilis, Prentki tions of NH4-N in wetlands. This is an et al. (1978) as 0.59-0.90 g P/m2/ yr in acceptable source of N for plants and, Typha lati/olia, and Brinson and Davis within limits, does no harm. Ammo (1976) as 0.13 mg P/m2/day in summer nium-N is not a substrate for denitrifi in Nuphar luteum. cation and is not converted to N2 and lost by that route. Cycle Syntheses Nitrogen is an ingredient in protein Brinson and Davis (1976), Klopatek and essential to animals. With higher (1975), and Richardson et al. (1978) have protein content than plants, animals and attempted to synthesize the N- or P many microorganisms serve essentially cycles within a wetland. Even in these as N concentrators, e.g., the bacteria cases, the water, vascular plant, and associated with decomposition as men sediment phases received most attention. tioned above. Animals also excrete N as Two different techniques were used urea, uric acid, or ammonia, generally changes in standing crops and radioiso .recycling it in the same area. Some im topes. Brinson and Davis found that pact of animal excreta on local N con their rate of uptake based on isotope centrations was inferred by Davies (1973) techniques was only 11% of uptake based for wintering waterfowl concentrations. on change in P standing crop. Hence, He cited an estimate (original reference their data on fluxes (Fig. 1) should be not given, unfortunately) of 90-250 mil considered in a relative sense only. The lion tons of N per year excreted by water important conclusions from Fig. 1 are: fowl. Without data on the area on which 1) uptake of P from both soil and water this is deposited, or its source, the net occurs in all seasons in Nuphar luteum impact cannot be evaluated. in North Carolina; 2) in summer P move Work on eelgrass (Zostera marina) ment occurs both from sediment through (McRoy et al. 1972), salt marshes (Rei the plant to water and to a lesser degree mold 1972), and freshwater macrophytes the reverse; 3) the sediment is the main (Demarte and Hartman 1974, Schroder source of P, and the interstitial and 1975, Brinson and Davis 1976, Lamarra dilute acid extractable fractions are more personal communication) suggests that than 100 times the maximum P in plants; living aquatic plants may actually give and 4) overall, the plants are a source of off P to the surrounding water. The rates P for the water, rather than the reverse. 2/day vary: 4.4 mg/m average for total P Klopatek (1975) studied an emergent, for Phragmites communis (Schroder Scirpus fluviatilis, in Wisconsin, mostly 1975), 2.5 mg/m2/day for Nuphar lu by standing crop determinations. On an teum in summer (Brinson and Davis annual basis, this species also moves or 1976), and 2.0-51.5 mg/m2/day from pumps Nand P from sediments to the Potamogeton alpinus (Lamarra personal water (Fig. 2). If it is assumed that water comm unication). is 50 ern deep and completely enclosed, Senescent but erect structures may the annual release of 2.2 g P/m2would lose nutrients by leaching. Klopatek result in a concentration in the water of (1975) estimated 2.2 g PIm2/yr lost by 4.4 mg P/1, far in excess of the observed
31 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
WINTER SPRING SUMMER although uptake and sedimentation with algal biomass are also a possibility. 310 310 Richardson et al. (1978) used methods similar to Klopatek's in a Michigan fen dominated by Chamaedaphne calyculuta Ptr P01 and Betula pumila (Figs. 3, 4). These are woody plants, so a substantial part of the above ground standing crop persists from year to year. In general, this ecosystem seems to be operating on 29 amounts and fluxes of P about an order 0' of magnitude less than Klopatek's Wis consin marsh. Nitrogen was also lower, BELOW but less so. GROUND 3584 Some further impression of Nand P in marsh systems can be gained from Uleh 4., 6.6 93 lova et al.'s (1973) study of Phrcamites communis in a fish pond in Czechoslova kia (Table 13). Basing calculations on those data, allowing for a life span of underground parts of 3 years, and sub tracting Nand P in standing dead indi- Fig. 1. The daily flux of P (mg) through a square meter of Nuphar luteum community ROLE OF EMERGENT MACROPHYTES IN MINERAL CYCliNG during the winter, spring, and summer. NITROGEN PHOSPHORUS Values in the compartmentsare P mass. Modi WATER WATER fiedfrom Brinsonand Davis(1976). (1.52 to 416 mg N/Uler) (0.11 to 0.69 mg P/I~er) 0.11 to 0.69 mg PII. Because the excess did not appear in the outflow, some method of immobilization must be postu lated. One possibility is that the Nand P liberated by macrophytes are taken up by algae and subsequently sedimented. Other workers (e.g., Tilton et al. 1976) have suggested a rapid incorporation in the sediments. Klopatek, whose data are 17.46 tr~7 summarized in Fig. 2, suggested that a --- --14 substantial fraction of "available" P in 2.03 0.44 the sediments was taken up by the plants. Indeed, his data suggested that the concentration of sediment P is reduced during the period of maximum plant uptake. Because of the greater SOIL SOIL (1696 9 N/m' I (12.1 g P/m' available P) amount of N than P available, relative to uptake, N depletion of the soil seems Fig. 2. Flow of Nand P through a Scirpus unlikely. The mechanism preventing N jluviatilis stand. Flows are in grams per enrichment of the water by the 7.34 g square meter per year, and compartments are N/m2 is likely denitrification rather grams per square meter in standing crop. than immobilization as in the case of P, From Klopatek(1975).
32 WATERFOWL AND WETLANDS SYMPOSIUM
PRECIPITATION (BULK) 0.41 (P04' P)
LIVE BIOMASS ~ V
242 <, UPTAKE ANNUAL NEW GROWTH ~ ------.--- \::J SOIL AVAILABLE (RIFLE PEAT) (P0 P) 4 (0-20 CM) (0'20 CM)
Fig. 3. A preliminary model showing annual P flux and storages for the leatherleaf and bog birch vegetation and soils components of a central Michigan peatland in 1975. All values are in g/rn-'. From Richardson et al. (1978).
6.2 PRECIPITATION (BULK)
TOTAL ABOVEGROUND "7'0'" LIVE BIOMASS
(6572)
UPTAKE ANNUAL NEW GROWTH
EXCHANGEABLE N SOIL (NH . t'<+N0 - N) (RIFLE PEAT) 4 3 (0-20 CM) 0-20 CM (26,9000)
Fig. 4. A preliminary model showing annual N flux and storages for the leatherleaf and bog birch vegetation and soils components of a central Michigan peatland in 1973. Total biomass for each compartment given in brackets. All values are in g/m2. From Richardson et al. (1978).
33 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
Table 13. Nutrient content in a Phrturmites communis stand (g/m2) (from Ulehlova et al. 1973).
N NH4 NOS P P04 Rainfall 0.80 0.06 Vegetation Living Aboveground stems 11.14 2.47 leaves 12.29 1.20 total 23.44 3.67 Underground rhizomes 19.06 8.45 roots 2.86 0.92 total 21.92 9.37 Total living 45.35 13.04 Standing dead stems 11.33 2.74 leaves 1.36 0.10 Total standing dead 12.69 2.84 Water 0.21 0.55 0.79 Sapropel 583 9.79 4.50 3.96 Bottom soil 270 6.90 2.25 3.75 cate a minimum annual uptake of 6.79 assume a marsh of 1 ha, average depth g P/m2 and 30.75 g N/m2. The combined 50 em, with a 10-ha catchment basin. All standing crops of P and inorganic N in water comes from rain, and the excess soil and water were inadequate to pro over evaporation leaves by an outflow vide that much P and N, indicating a channel. The watershed is agricultural substantial input during the year. The land, one-half cropland and one-half very high ortho-P content of the water pasture. Annual rainfall is 50 em. As 1.96-3.19 mg/l as P04 - suggests the sume 0.5 ha Typha, 0.5 ha Ceratophyt possibility that the fish pond studied was tum, and annual plant uptake of Nand P fertilized. == annual plant loss. Then we can con struct hypothetical budgets for water, N, and P, using values selected from OVERVLEWANDMANAGEMENT existing studies, cited previously, plus In preceding sections the data on some guesses, and allocating residuals to processes and storages affecting Nand P storage in the sediments (Table 14). cycling in wetlands were analyzed. The The resulting hypothetical balances emphasis was on biological processes, illustrate several key points. First, such with comparative neglect of the physical a marsh accumulates nutrients, consis chemical. To put the general aspects of tent with generally held opinion. Nitro these cycles into perspective, let us as gen and phosphorus dissolved in the sume a hypothetical marsh on the water and available in sediments are eastern edge (about longitude 100° W) of grossly inadequate for plant uptake, indi the prairies at mid-latitude. Further cating that the supply must be renewed
34 WATERFOWL AND WETLANDS SYMPOSIUM
Table 14. Hypothetical annual H20, N, and P budgets for a wetland. H2O P N Process or storage (md/yr) (kg/ha/yr) (kg/ha/yr) Hydrologic Precipitation input 5,000 0.25 5 Runoff from cropland (20% precipitation) 5,000 22.0 37.5 Runoff from pasture 5,000 0.85 42.5 Total runoff inputs 10,000 22.85 80.0 Evapotranspiration loss 5,000 Outflow (0.3 mg PII, 2 mg Nil) 10,000 3 20 Net change 0 +20.10 +65.0
Internal cycles
Storage in H20 (0.1 mg P II, 1 mg Nil) 5,000 0.5 5.0 Storage in sediment (roughly root zone) Total 600-1,600 40-2,000 3,000-17,000 "Available" 3 8 Stored in Typha standing crop 15 75 (3 g P/m2, 15 g N/m2) Stored in Ceratophyllum standing crop 6.5 83.5 (1.3 g P1m 2, 16.7g N/mZ) Total in above ground plants 21.5 158.5 Plant uptake
Typha (3.5 g P/m2, 20 g N/m2) 17.5 100.0 Ceratophyllum (1.5 g P/m2, 20 g N/m2) 7.5 100.0 Total uptake, mostly from sediment 25.0 200.0 Input to H20 via decomposition and leaching 13.0 80.0 Input to sediment and litter from plant remains 8.0 100.0 Animal consumption (cycled to same year) 2.0 20.0 Release from plants to H2O (2mgP/m 2/day, 100 days) 2.0 Potential net N loss: denitrification-nitrogen fixation 7.0
35 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
rapidly by processes such as runoff and Imports of nutrients, either by runoff release from sediment storage. Inputs to or direct addition (fertilization), are to the water from decomposition and leach some degree controllable by the manager. ing would greatly increase dissolved con Some studies of wetland fertilization are centrations unless some mechanisms underway or have been completed result in immobilization. Looked at recently (Kadlec 1976, Boyd 1~71a, Odum another way, the bulk of the Nand P for et al. 1976, Steward and Ornes 1973, plant growth apparently comes from and Moreau 1976). Plant response has often returns to the sediment, with only an been less than expected, even under ephemeral existence dissolved in surface greenhouse conditions (Wentz 1976). In water. Both the runoff and decomposi several cases, uptake by sediments and tion inputs to the water could raise P denitrification have removed most of the concentrations from about 0.1 mg/l to added Nand P, with only a fraction going 2.5-4.0 mg/l and N concentrations from to the plants (several studies suggest about 1 mg/l to about 16 mg/l. Such about 25% - e.g., Patrick et al. 1974 concentrations seem to occur rarely, if reported 17-23% of 56 and 112 kg N/ha) ever, and hence the inference of some but nevertheless increasing yield sub mechanisms re-sedimenting the P and stantially. perhaps N. For N, there is the alternative Sediments vary enormously in the that net gaseous loss (N-fixation minus total amount of Nand P stored, depend denitrification) might be a major pro ing on both physical structure and cess, far greater than the 7 kg/ha/yr chemical state. Further, I believe they estimated. Data exist to justify estimates vary in the ease with which nutrients are as high as several hundred kg/ha/yr. flushed out by water movements. Cook Chemical precipitation could easily and Powers (1958) suggested that marsh account for the P sedimentation, and drainage at the wrong time could result there is a clear implication of P enrich in a substantial loss of nutrients. To my ment of the sediments. We don't know if knowledge, this aspect of the relationship this occurs, nor whether that P is avail between marsh hydrology and nutrient able for future plant growth, nor if P cycles has not been carefully studied and concentrations in the interstitial water evaluated. Several workers (Lee et al. or surface water increase with time. 1975, Kadlec 1976, Klopatek 1975) have From a management point of view, it found higher nutrient levels in water seems clear that runoff inputs and coming from marshes in early spring, processes associated with sediment stor which suggests a flushing effect. The age are likely to dominate the system. importance of this phenomenon to the Again, this is consistent with observa marsh is not yet clear. tions that the productivity of marshes is In sum, the overall budgets of Nand P correlated with the fertility of their seem to be strongly dominated by the watersheds. The effects of drawdowns or rates at which Nand P are supplied and natural drought on marsh sediments and removed. Surface runoff seems to be a productivity are reasonably well known dominant supply route, perhaps reaching (Weller 1978, Kadlec and Wentz 1974). its peak in riverine marshes. Removal Until recently the possible importance of seems to be mainly through processes denitrification in marshes seems to have associated with the sediments, but poten been less widely appreciated, although it tially also through water outflow and has been considered a serious problem in denitrification. Limnologists have found the culture of rice (Patrick and Mahapa that the trophic state (fertility) of lakes tra 1968). is dominated by: 1) nutrient import, or
36 WATERFOWL AND WETLANDS SYMPOSIUM
loading, and 2) a measure of the time ly, the aim of management will be to water remains in the lake, or turnover conserve and increase supplies of avail rate. able N, P, and other nutrients. In Aquatic and marsh plants take up and managing water, the manager should return to water and sediments large attempt to hold water high in nutrients amounts of both Nand P. Their role in as long as possible; conversely, water nutrient cycling seems to be one of ex released should be low in nutrients. tracting nutrients from deeper sediments Mechanisms and processes internal to and returning them to surface sediments the marsh may tend to do this naturally, and to the water to some degree (Prentki but managing to increase retention time et al. 1978). The available evidence does of nutrient rich water should be benefi not suggest that vascular plants are very cial. Of course, should excess nutrients, effective in regulating or reducing e.g., salt, be a problem, the reverse pro nutrients in surface waters, although cedure is called for. they will certainly respond to increased The productivity of marsh sediments nutrients with increased growth. This is often improved by temporary drain view of the role of aquatic vascular age; hence the frequent practice of plants in nutrient cycling seems to con periodic drawdown as a marsh manage flict with the generality that water ment technique. Certainly this practice basins tend to accumulate and store affects physical and chemical processes, nutrients in the natural process of eutro but the microbiological effects may be phication. The conflict is real only to the even more dramatic, e.g., nitrification. extent that nutrients are not sedimented Most of our knowledge of drawdown in forms unavailable to plants in insolu effects is empirical, and some careful ble minerals or decay resistant organic research is needed on the processes af debris. Certainly the plants tend to keep fected by water level manipulation. For the soluble and available nutrients in example, water level fluctuations, parti current circulation. It is probably unwise cularly on a short time scale of, say, a to pursue these generalities further with few days, may greatly increase denitrifi out more information. cation and lead to N deficiencies. This What should a manager do? Few has not been demonstrated in marshes, marshes suffer from an oversupply of to my knowledge, but seems possible and available Nand P for growth of plants should be considered in future research desirable for waterfowl habitat. General and management.
37 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
LITERATURE CITED ANDERSEN, V. J. M. 1974. Nitrogen and BRINSON, M. M., AND G. J. DAVIS. 1976. phosphorus budgets and the role of sedi Primary productivity and mineral cycling ments in six shallow Danish lakes. Arch. in aquatic macrophyte communities of Hydrobio!. 74(4):528-550. the Chowan River, North Carolina. Univ. N. Carolina Water Resour. Res. Inst. Rep. ANDERSON, M. G., AND J. B. LOW. 1976. 120. 137pp. Use of sago pond weed by waterfowl on the Delta Marsh, Manitoba. J. Wild!. BURGESS, H. H. 1969. Habitat management Manage. 40(1):233-242. on a mid-continent waterfowl refuge. J. Wild!. Manage. 33(4):843-847. BERNATOWICZ, S. 1969. Macrophytes in the CARPENTER, S. R., AND M. S. ADAMS. Lake Warniak and their chemical com 1977. The macrophyte tissue nutrient pool position. Ekologia Polska-Seria A. of a hardwater eutrophic lake: implica 17(27):1-20. tions for macrophyte harvesting. Aquat. BOYD, C. E. 1967. Some aspects of aquatic Bot. 3(3):239-255. plant ecology. Pages 114-129 in Sympo CHAMIE, J. P. M. 1976. The effects of simu sium on reservoir fishery resources. lated sewage effluent upon decomposi University of Georgia Press, Athens. tion, nutrient status and litter fall in a __ . 1970a. Losses of mineral nutrients central Michigan peatland. Ph.D. Thesis. during decomposition of Typha latifolia. Univ. of Michigan, Ann Arbor. 110pp. Arch. Hydrobiol. 66(4):511-517. COLE, G. A. 1975. Textbook of limnology. ___ . 1970b. Production, mineral accumula Mosby, St. Louis. 281pp. tion and pigment concentrations in Typha COOK, A. H., AND C. F. POWERS. 1958. laiifolui and Scirpus americanus. Ecology Early biochemical changes in the soils 51(2):285-290. and waters of artificially created marshes ___ . 1971a. Further studies on producti in New York. New York Fish Game J. vity, nutrient and pigment relationships 5(1):9-65. in Typha laiifolia populations. Bul!. Tor CRISP, D. T. 1966. Input and output of rey Bot. Club 98(3): 144·150. minerals for an area of pennine moor __ . 1971b. The limnological role of aqua land: the importance of precipitation, drainage, peat erosion and animals. tic macrophytes and their relationship to J. reservoir management. Pages 153-166 in Appl. Eco!. 3(2):327-348. Reservoir Fisheries and Limnology. Am. DA VIES, D. W. 1973. The relationship Fish. Soc. Publ. 8. between waterfowl and nitrogen species ___ . 1978. Chemical composition of wet in the waters of the Bosque Del Apache. M. S. Thesis. New Mexico Inst. of Mining land plants. Pages 155-167 in R. E. Good, and Technology, Socorro. 52pp. D. F. Whigham, and R. L. Simpson, eds. Freshwater wetlands: ecological proces DAVIS, C. B., AND A. G. VAN DER VALK. ses and management potential. Academic 1978. The decomposition of standing and Press, New York. fallen litter of Typha glauca and Scirpus fluviatilis. Can. J. Bot. 56(4):662-675. __ , AND L. W. HESS. 1970. Factors in DELAUNE, R. D., W. H. PATRICK, JR., fluencing shoot production and mineral AND J. M. BRANNON. 1976. Nutrient nutrient levels in Typha Iatifolia. Ecology transformations in Louisiana salt marsh 51(2):296-300. soils. Louisiana State Univ. Cent. for BRANNON, J. M., R. M. ENGLER, J. R. Wetland Res., Sea Grant Pub!. LSU-T ROSE, P. G. HUNT, AND I. SMITH. 76-009. 38pp. 1976. Selective analytical partitioning of DEMARTE, J. A., AND R. T. HARTMAN. sediments to evaluate potential mobility 1974. Studies on absorption of 32p, 59Fe, of chemical constituents during dredging and 45Ca by water-milfoil (Myriophyllum and disposal operations. U.S. Army Engi exalbescens Fernald). Ecology 55(1):188 neer Waterways Tech. Rep. D-76-7. 90pp. 194.
38 WATERFOWL AND WETLANDS SYMPOSIUM
DILLON, P. J., AND F. H. RIGLER. 1974. Ranch peatland. Pages 42-64 in R. H. A test of a simple nutrient budget model Kadlec, C. J. Richardson, and J. A. Kad predicting the phosphorus concentration lec, eds. The effects of sewage effluent in a lake water. J. Fish. Res. Board Can. on wetland ecosystems. Semi-annual 31(11):1771-1778. Report No.2 NSF-RANN. National DYKYJOVA, D., AND D. HRADECKA. 1973. Science Foundation, Washington, D.C. Productivity of reed-bed stands in rela tion to the ecotype, microclimate, and KEENEY, D. R., R. 1. CHEN, AND D. A. trophic conditions of the habitat. Polish GRAETZ. 1971. Importance of denitrifi Arch. Hydrobiol. 20(1):111-119. cation and nitrate reduction in sediments EVANS, H. J., AND L. E. BARBER. 1977. in the nitrogen budget of lakes. Nature Biological nitrogen fixation for food and 233(5314):66-67. fiber production. Science 197(4301):332 KITCHENS, W. M., J. M. DEAN, L. H. STE 339. VENSON, AND J. H. COOPER. 1975. The Santee Swamp as a nutrient sink. FEKETE, A. 1973. The release of phosphorus Pages 349-366in Mineral cycling in south from pond sediments and its availability eastern ecosystems. U.S. Energy Re to Lemna minor L. M. S. Thesis. Rutgers search and Development Administration, Univ., New Brunswick, NJ. 70pp. Washington, D. C. GAUDET, J. J. 1977. Uptake, accumulation KLOP ATEK, J. M. 1975. The role of emergent and loss of nutrients by papyrus in tropi macrophytes in mineral cycling in a cal swamps. Ecology 58(2):415-422. freshwater marsh. Pages 367-393 in GERLOFF, G. C., AND P. H. KROMBHOLZ. Mineral cycling in southeastern eco 1966. Tissue analysis as a measure of systems. U.S. Energy Research and nutrient availability for the growth of Development Administration, Washing angiosperm aquatic plants. Limnol. ton, D.C. Oceanogr.11(4):529-537. KOLLMAN, A. L., AND M. K. WALl. 1976. HARRIS, S. W., AND W. H. MARSHALL. Intraseasonal variations in environmen 1963. Ecology of water-level manipula tal and productivity relations of Potamo tions on a northern marsh. Ecology 44(2): geton pectinatus communities. Arch. 331-343. Hydrobiol. 50(4):439-472. HUTCHINSON, G. E. 1975. A treatise on lim KOMARKOVA, J., AND J. KOMAREK. 1975. nology. Vol. III-Limnological botany. Comparison of pelagial and littoral pri John Wiley and Sons, New York. 660pp. mary production in a south Bohemian KADLEC, J. A. 1960. The effect of a draw fishpond (Czechoslovakia). Pages 77-95 down on the ecology of a waterfowl im inJ. Salanki and J. Ponyi, eds. Limnology poundment. Michigan Dept. Conserv. of shallow waters. Akadeniai Kiado Game Div. Rep. 2276. 181pp. Budapest. ___ . 1976. Dissolved nutrients in a peat KVET, J. 1973. Mineral nutrients in shoots of land near Houghton Lake, Michigan. reed (Phragmites communis Trin.). Polish Pages 25-50 in D. L. Tilton, R. H. Kadlec, Arch. Hydrobiol. 20(1):137-147. and C. J. Richardson, eds. Freshwater ___ . 1975. Growth and mineral nutrients wetlands and sewage effluent disposal. in shoots of Typha latifolia L. Pages 113 Proc. 1976 Symp., Ann Arbor, MI. Na 123 in J. Salanki and J. Ponyi, eds. Lim tional Science Foundation, Washington, nology of shallow waters. Akadeniai D.C. Kiado, Budapest. __ , AND W. A. WENTZ. 1974. State-of the-art survey and evaluation of marsh LAMARRA, V. A., JR. 1975. Digestive activi plant establishment techniques: induced ties of carp as a major contributor to the and natural. Vol. 1: Report of research. nutrient loading of lakes. Verh. Internat. U.S.A. Coastal Engineering Res. Cent. Verein. Limnol. 19:2461-2468. Final Rep. 231pp. LEE, G. F., E. BENTLEY, AND R. AMUND KASISCHKE, E. R. 1974. Algae of the Porter SON. 1975. Effects of marshes on water
39 NITROGEN AND PHOSPHORUS DYNAMICS IN WETLANDS
quality. Pages 105-127 in A. D. Hasler, ed. soils. Pages 323-359 in Advances in ag Coupling of land and water systems. ronomy. Vol. 20. Academic Press, New Springer-Verlag, New York. York. LIKENS, G. E. 1975. Nutrient flux and cycling __ , AND K. R. REDDY. 1976. Fate of in freshwater ecosystems. Pages 314-348 fertilizer nitrogen in a flooded rice soil. in Mineral cycling in southeastern eco Soil. Sci. Soc. Am. J. 49(5):678-681. systems. U.S. Energy Research and PRENTKI, R. T., T. D. GUSTAFSON, AND Development Administration, Washing M. S. ADAMS. 1978. Nutrient movements ton, D.C. in lakeshore marshes. Pages 169-194 in MAGUIRE, L. A. 1974. A model of beaver R. E. Good, D. F. Whigham, and R. L. population and feeding dynamics in a Simpson, eds. Freshwater wetlands: peatland at Houghton Lake, Michigan. ecological processes and management M. S. Thesis. Univ. of Michigan, Ann potential. Academic Press, New York. Arbor. 127pp. REDDY, K. R., AND W. H. PATRICK, JR. McCOLL, J. G., AND J. BURGER. 1976. 1976. Effects of frequent changes in aero Chemical inputs by a colony of Franklin's bic and anaerobic conditions in redox gulls nesting in cattails. Am. MidI. Nat. potential and nitrogen loss in a flooded 96(2):270-280. soil. Soil BioI. Biochem. 8:491-495. McROY, C. P., R. J. BARSDATE, AND M. REIMOLD, R. J. 1972. The movement of phos Nitrogen utilization by rice using N phorus through the salt marsh cord grass, eelgrass (Zostera marina L.) ecosystem. Spartina olterniflora 1. Limnol. Ocean Limnol. Oceanogr. 17(1):58-67. ogr.17(4):606-611. MEEKS, R. L. 1969. The effect of drawdown RICHARDSON, C. J., D. L. TILTON, J. A. date on wetland plant succession. KADLEC, J. P. M. CHAM IE, AND J. Wildl. Manage. 33(4):817-821. W. A. WENTZ. 1978. Nutrient dynamics MOORE, P. D., AND D. J. BELLAMY. 1974. in northern wetland ecosystems. Pages Peatlands. Springer-Verlag, New York. 217-241 in R. E. Good, D. F. Whigham, 222pp. and R. L. Simpson, eds. Freshwater wet MOREAU, G. D. 1976. Effects offertilizers on lands: ecological processes and manage aquatic vegetation. M. S. Thesis. Utah ment potential. Academic Press, New State Univ., Logan. 52pp. York. ODUM, H. T., K. C. EWEL, J. W. ORDWAY, RYKIEL, E. J. 1977. Toward simulation and AND M. K. JOHNSTON. 1976. Cypress systems analysis of nutrient cycling in wetlands for water management recycl the Okefenokee Swamp, Georgia. Dept. ing and conservation. Third Annual Re Zoology and Inst. Ecol., Okefenokee Eco port to NSF and Rockefeller Foundation. system Investigation Tech. Rep. 1. Univ. Center for Wetlands, Univ. of Florida, Georgia, Athens. 139pp. Gainesville. 879pp. RYTHER, J. H., AND W. M. DUNSTAN. PATRICK, W. H., R. D. DELAUNE, R. M. 1971. Nitrogen, phosphorus and eutrophi ENGLER, AND S. GOTOH. 1976. Nitrate cation in the coastal marine environment. removal from water at the water-mud Science 171 (3975):1008-1013. interface in wetlands. U.S. Environmen SCHRODER, R. 1975. Release of plant tal Protection Agency, EP A-600/3-76-042. nutrients from reed borders and their NTIS, Springfield, VA. 80pp. transport into the open waters of the __, __, AND F. J. PETERSON. 1974. Bodensee-Untersee. Pages 21-28 in J. Nitrogen utilization by rice using 15N_ Salanki and J. Ponyi, eds. Limnology of depleted ammonium, Agron. J. 66(6):bI9 shallow waters. Akademiai Kiado, Buda 820. pest. __ , AND I. C. MAHAPATRA. 1968. SCHULTHORPE, C. D. 1967. The biology of Transformation and availability to rice of aquatic vascular plants. St. Martin's nitrogen and phosphorus in waterlogged Press, New York. 610pp.
40 WATERFOWL AND WETLANDS SYMPOSIUM
STEWARD, K. K., AND W. H. ORNES. 197:3. cial marshes. Pages 21-34 in R. E. Good, Assessing the capability of the Ever D. F. Whigham, and R. L. Simpson, eds. glades marsh environment for renovating Freshwater wetlands: ecological proces wastewater. South Florida Environmen ses and management potential. Academic tal Project, Ecol. Rep. DI-SFEP-74-06. Press, New York. National Park Service, Washington, D. C. 13pp. VOLLENWEIDER, R. A.. 1968. Scientific fundamentals of the eutrophication of __ , and __ . 1975. The autecology of lakes and flowing waters, with particular sawgrass in the Florida Everglades. reference to nitrogen and phosphorus as Ecology 56(1):162-171. factors in eutrophication. UN Organ. TILTON, D. L., R. H. KADLEC. AND C. J. Econ. Cult. Devel. 27:1-159. RICHARDSON, eds. 1976. Freshwater WELLER, M. W. 1978. Management of wetlands and sewage effluent disposal. marshes for wildlife. Pages 267-284 in Proc. 1976 Syrnp.. Ann Arbor, MI. Na R. E. Good, D. F. Whigham, and R. L. tional Science Foundation, Washington, Simpson, eds. Freshwater wetlands: D.C. 343pp. ecological processes and management TOETZ, D. W. 1973. The kinetics of NH up potential. Academic Press, New York. take by Ceratophyllum. Hydrobiologia WENTZ, A. W. 1976. The effects of simulated 41(3):275-290. sewage effluents on the growth and pro ULEHLOVA, B., S. HUSAK, AND J. ductivity of peatland plants. Ph.D. DVORAK. 1973. Mineral cycles in reed Thesis. Univ. of Michigan, Ann Arbor. stands of Nesyt fishpond in Southern 112pp. Moravia. Polish Arch. Hydrobiol. 20(1): WHIGHAM, D. F., J. McCORMICK, R. E. 121-nL GOOD, AND R. 1. SIMPSON. 1978. Bio VALLE~TYNE,J. R. 1952. Insect removal of mass and primary production of fresh nitrogen and phosphorus compounds water tidal marshes. Pages 3-20 in R. E. from lakes. Ecology 33(4):573-577. Good, D. f. Whigham, and R. L. Simpson, eds. Freshwater wetlands: ecological VAN DER VALK, A. G., AND C. B. DAVIS. processes and management potential. 1978. Primary production of prairie gla Academic Press, New York.
41
WATERFOWL AND WETLANDS ANINTEGRATED REVIEW
Proc. 1977Syrnp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
SPATIAL AND TEMPORAL HABITAT RELATIONSHIPS OF BREEDING DABBLING DUCKS ON PRAIRIE WETLANDS
DAVID L. TRAUGERl and JEROME H. STOUDT
U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401
Abstract: The U.S. Fish and Wildlife Service established several waterfowl study areas in Canada during the early 1950's. Annual waterfowl and habitat surveys were conducted near Lousana, Alberta, Redvers, Saskatchewan, and Minnedosa, Manitoba, into the late 1970's. Observations were recorded during an era of wet-dry-wet habitat cycles, liberal-restrictive liberal hunting regulations, increasing intensity of land use, and accelerating rate of wetland alteration. Data from these areas located in the prairie parklands provide biologists and managers with unique opportunities to assess waterfowl population and production trends over the past three decades. Dramatic shifts in species composition and abundance were documented in response to habitat changes as well as hunting regulations. The species with declining num bers generally tend to be those heavily harvested, whereas the species with stable or increasing populations tend to be those lightly harvested. There are also relationships between breeding chronology and relative abundance: early breeders are not holding up as well as late breeders. Pond occupancy rates indicate that the decline in waterfowl populations is occurring more rapid ly than losses of wetland habitat. There is an increasing number of ponds without ducks, sug gesting that the available breeding habitat is underutilized. The rapid conversion and intensifi cation of land use is continuing on an ever-increasing scale with impact on both the quality and quantity of wetland and upland waterfowl production habitat. If recent years are any preview of the future, the face and character of prairie Canada may be altered by prevailing socio economic conditions. High grain prices have markedly altered agricultural practices in response to world food shortages and populations trends. The upshot of these events has been depressed reproductive potential for several waterfowl species.
IPresent address: Division of Wildlife Ecology Research, U.S. Fish and Wildlife Service, Washington, D.C. 20240.
WATERFOWL AND WETLANDS ANINTEGRATED REVIEW
Proc. 1977Symp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
SOCIAL INTERACTIONS AND SPACING BEHAVIOR IN BREEDING DABBLING DUCKS
SCOTT R. DERRICKSON
Endangered Species Research Program, Patuxent Wildlife Research Center, Laurel, Mary land 20811
Abstract: Although dabbling ducks are gregarious during most of the year, pairs of most species seek some degree of isolation during particular phases of the breeding season. The behavioral responses of pairs to conspecifics vary in relation to both breeding status and breeding chronology. In the present paper, discussion centers upon pair-bond characteristics, pair-spacing patterns, pursuit flights, male mate-support roles, and male promiscuity. Strong pair-bonds are generally correlated with low mobility and territoriality, distant threat displays, pronounced male-male hostility, and reduced male promiscuity. Conversely, weak pair-bonds are correlated with increased mobility, reduced territoriality, reduced male-male hostility, and increased male promiscuity. Interspecific differences in evolved breeding strategies are apparent, and appear to reflect differences in habitat characteristics, feeding ecology, and the energetic requirements of breeding females.
45
WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Symp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
FOODS OFLAYING FEMALE DABBLING DUCKS ON THE BREEDING GROUNDS
GEORGE A. SWANSON, GARY L. KRAPU, AND JEROME R. SERlE
U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401
Abstract: Food of laying hens of five species of dabbling ducks collected in the glaciated prairie pothole region of south central North Dakota consisted largely of invertebrates: 99% in blue winged teals (Anas discDrs) and shovelers (A. clypeata); 70% in mallards (A. platyrhynchos); 77% in pintails (A. acuta); and 72% in gadwalls (A. strepera). Snails and aquatic insects domi nated the diet of blue-winged teals, snails and crustacea the diet of shovelers, and insects and crustacea the diet of gadwalls. Earthworms were an important food of female mallards and pintails during wet years. Dominant plant components consumed were filamentous algae by gadwalls and plant fruits by mallards and pintails. Factors that influenced the selection of food items were nesting chronology and food availability. Food availability was determined primarily by the life cycle and behavior of invertebrates and current hydrological conditions within the wetland complexes. During years of adequate precipitation, temporary, seasonal, and semiper manent wetlands provided abundant and highly available plant and animal foods successively throughout the breeding season. Prairie wetland complexes provide an important habitat component in the ecology of prairie dabbling ducks. Adequate preservation of waterfowl produc tion habitat requires that the importance of the wetland complex be stressed.
Prairie wetlands traditionally used by well documented. Siltation, tillage, and breeding waterfowl are being altered or chemical contamination are examples of eliminated throughout the glaciated potentially degrading influences on wet prairie pothole region of North America. land quality and subsequently on the The loss of wetlands caused by partial or availability of foods for breeding water complete drainage is dramatic and can be fowl. readily documented; however, effects of The semi-arid climate is a dominant the more subtle ecological changes that factor affecting the hydrology and con alter the structure of plant and animal sequently the ecology of wetlands in the communities are less obvious and not glaciated prairie pothole region of North
47 FOODS OF LAYING FEMALE DABBLING DUCKS
America. An annual moisture deficit, and undergo drawdowns or dry up which varies in magnitude and is accom during periods of drought. These wet panied by changes in annual and sea lands contain deep marsh emergent and sonal water levels and dissolved salts, is submerged vascular plants and a number a dominant feature of the semi-arid of invertebrate species that are suscep climate. Plant and animal communities tible to dry conditions. As the salt con continually change in response to these tent of the water increases, salt tolerant fluctuations in water level and salt con plant and animal species begin to domi tent (Swanson and Meyer 1977), and nate the biotic communities (Swanson et periodic droughts produce major changes al. 1974). in plant and animal communities. The Kantrud and Stewart (1977) described dynamic nature of this water regime and use of natural basin wetlands in North the successional changes in the biota that Dakota by breeding pairs of ducks. it produces are beneficial for dabbling Temporary, seasonal, and semiperma ducks. Plant and animal foods are often nent wetlands were used extensively by abundant and available at shallow pairs of dabbling ducks, whereas per depths to dabbling ducks throughout the manent lakes were generally used breeding season. relatively little. Temporary and seasonal Prairie wetlands are shallow, non wetlands received the highest proportion integrated, eutrophic, alkaline, and high of annual use by breeding pairs. Tilled in dissolved solids, and contain a low wetlands received less use than did relief, featheredged shoreline. Small undisturbed wetlands. changes in water volume produce major Adequate assessment of the effects of changes in the surface area inundated or changes in aquatic ecosystems on water exposed by drawdown. This interaction fowl ecology requires an understanding of climate and surface geology produces of the feeding niches occupied by the dynamic and productive aquatic ecosys different species of waterfowl. Know tems, which are essential to breeding ledge of feeding niches will provide waterfowl. wetland managers with information Stewart and Kantrud (1971) developed needed to define critical and threatened a classification system for prairie wet habitat, preserve wetlands of highest lands based on species structure of quality, and efficiently manage existing vegetation zones, as determined by water wetland habitat. permanence and variations in average Early investigations of foods con salinity. Ephemeral, temporary, and sumed by dabbling ducks often combined seasonal wetlands typically undergo information derived from different drawdowns each year and contain plant species, sexes, seasons, and geographical and animal communities that vary in areas, and the data were dominated by their tolerance of dry conditions. Inverte fall and winter collections. Data were brates that thrive on a detritus or algal collected during the fall, in part, because food chain are abundant during the of the availability of birds killed by waterfowl breeding season, and are hunters. Few attempts were made to available to anatids because of the identify foods consumed by dabbling shallow water depths. Temporary and ducks during the breeding period (Perret seasonal wetlands also provide loafing 1962:4). Some authors pointed out, how sites for pairs and reduce intraspecific ever, that more animal foods appeared to strife. be consumed during the breeding season Semipermanent wetlands are flooded than during other times of the year throughout the year during wet cycles (Martin and Uhler 1939:98, Stewart
48 WATERFOWL AND WETLANDS SYMPOSIUM
1962:44). water quality, and biota of this area were Bartonek (1968:92) reviewed 125 pub described by Eisenlohr (1972), Sloan lished studies of waterfowl food habits (1972), Stewart and Kantrud (1972), and concluded that 95% contained and Swanson et al. (1974). Actively feed material that biased data in favor of ing birds were collected, and only the seeds. More recent investigations have esophageal contents, measured by pointed out the bias associated with use volumetric displacement, were tabulated. of the gizzard for food studies when a Food items are expressed as the mean of variety of foods that vary in hardness is volumetric percentages (aggregrate consumed (Dillon 1958, Moyle 1961, percent). Ovaries were examined so that Perret 1962, Dirschl 1969, Bartonek and food consumption could be correlated Hickey 1969, Swanson and Bartonek with reproductive condition. Feeding 1970). sites were examined to provide a basis More recent investigations of foods for determining food selectivity. Data consumed by dabbling ducks have docu are presented on two groups of laying mented a high incidence of animal foods gadwalls: (1) those that fed in saline in the diet of breeding birds (Dirschl lakes located in glacial outwash, and (2) 1969, Bartonek 1972), particularly hens those that fed in ephemeral, temporary, (Perret 1962, Swanson and Nelson 1970, seasonal, and fresher semipermanent Krapu 1974a, Swanson et al. 1974, Serie lakes located in end and ground moraines. and Swanson 1976, Landers et al. 1977, Swanson and Meyer 1977). An increase in the consumption of animal foods RESULTS AND DISCUSSION during egg formation has been demon strated (Krapu 1974a, Serie and Swanson Food Selection 1976). The objectives of this paper are to: (1) Among plant and animal foods con describe the foods consumed by the sumed by laying female dabbling ducks laying hens of five species of dabbling of 5 species, invertebrates accounted for ducks, and (2) assess the role of com 99% in blue-winged teals and shovelers, plexes of wetlands in providing spatial 70% in mallards, 77% in pintails, and and temporal requirements of ducks 72% in the 2 groups of gad walls. during the breeding season. Foods selected by laying females Appreciation is extended to M. 1. varied among species (Table 1). Snails Meyer for aid in the laboratory and H. F. and aquatic insects dominated the diet of Duebbert and A. T. Klett (Northern blue-winged teals, snails and crustacea Prairie Wildlife Research Center) for the diet of shovelers, and insects and critical review of the manuscript. crustacea the diet of gadwalls. Earth worms were an important food of mal METHODS lards and pintails during early spring. Filamentous algae formed a major part Methods used in this study were of the plant matter consumed by gad described by Krapu (1974a), Swanson et walls, and fruits were dominant plant al. (1974), and Serie and Swanson (1976). parts eaten by mallards and pintails. Birds were collected while actively feed Snails are a major food item in the diet ing during 1967-76 within the drift plain of blue-winged teals on the breeding and Missouri Coteau areas of the Prairie grounds (Dirschl 1969, Swanson et al. Pothole Region in south central North 1974). During the laying period, molluscs Dakota. The geology, hydrology, climate, accounted for 40% of the diet of female
49 FOODS OF LAYING FEMALE DABBLING DUCKS
Table l. Aggregate percent volume of foods consumed by laying female Anatidae collected during 1969-76in south central North Dakota (number of birds examined shown in parentheses).
Blue-winged Gadwall Gadwall Food item teal a Shoveler b (saltl- (fresh)d Mallard'' Pintail r (20) (15) (20) (35) (15) (31) MOLLUSCA 40 40 4 14 15 Gastropoda 38 40 4 14 15 Lymnaea spp. 28 18 t g 14 Uh Gyraulus spp. 5 12 t U Miscellaneous 5 10 4 U Pelecypoda 2 INSECTA 44 5 52 36 14 37 Trichoptera 7 t 1 8 1 Odonata 1 t 2 6 5 Coleoptera 3 2 16 4 t 3 Hemiptera 1 1 7 t Lepidoptera 7 Diptera 32 2 26 18 2 33 Chironomidae 20 1 26 17 1 20 CRUSTACEA 14 54 20 32 16 14 Anostraca 5 6 t t 14 Conchostraca t 7 14 9 t Copepoda t 5 5 Ostracoda 1 3 5 7 t Cladocera 33 10 10 6 Amphipoda 8 1 1 ANNELIDA 1 26 11 Oligochaeta 1 24 11 Aquatic t Terrestrial 1 24 11 Hirudinea 2 VEGETATION 27 25 3 Algae (filamentous) 22 9 Lemnaspp. t 8 Miscellaneous 5 8 3 FRUITS 1 1 3 27 23 Echinochloa crusgalli 15 8 Miscellaneous 1 1 3 12 15 a Swanson and Meyer 1977. b Swanson, unpublished data. c Serie and Swanson 1976. "Salt" gadwalls are those that fed in saline lakes. d Swanson, unpublished data. e Swanson, unpublished data. f Krapu 1974a. g Less than 1 %. h Genera of gastropods unidentified.
50 WATERFOWL AND WETLANDS SYMPOSIUM
blue-winged teals and shovelers, 14% of lands were the primary crustacean in the diet of mallards, and 15% of the diet the diet of pintails. The fairy shrimp of pintails. Shovelers ate a greater consumed by blue-winged teals and proportion of small planorbid snails. shovelers, however, were species found Female gadwalls consumed fewer snails only in lakes high in dissolved salts, (4%) than did the other species. Saline Clam shrimp (Conchostraca) were an lakes do not support snails, except in important food of shovelers, mallards, adjacent fen areas, but fresher wetlands and the gadwalls that fed on lakes in selected as feeding sites by breeding gad moraines that were low in dissolved salts. walls contained high snail populations. Cladocera, copepods, and ostracods were The snails selected by gadwalls were a consumed primarily by shovelers and thin shelled, semi-aquatic form (Suc gadwalls. Amphipods were eaten pri cinea spp.) that was not found in the marily by blue-winged teals, which other ducks. consumed Hyalella azteca by feeding in The dominant snails eaten by all and around plant stems and terminal species of ducks examined except the buds. Perret (1962:64) also noted that gadwall were Lymnaea spp. Lymnaea mallards did not use this food. Amphi stagnalis, a larger species often abun pods, an abundant group found in most dant in semipermanent lakes, was not semipermanent wetlands and permanent found in laying females. Snails are an lakes, form a major part of the diet of important food nutritionally because lesser scaups (Aythya affinis) during the they provide high levels of protein and breeding season (Rogers and Korschgen calcium, both of which are required by 1966, Bartonek and Hickey 1969, Dirschl laying hens (Krapu and Swanson 1975). 1969, Bartonek and Murdy 1970). Aquatic insects were major foods in Terrestrial earthworms were con the diet of blue-winged teals (44%), pin sumed by dabbling ducks after they were tails (37%), and the two groups of gad washed into wetlands during early walls (52 and 36%). Insects accounted for spring storms. Laying mallards and 14% of the diet in mallards and 5% in pintails ate earthworms in early spring shovelers. Caddis fly larvae (Trichop when this food was abundant in compari tera), dragonflies (Odonata), damselflies son with other invertebrates, which were (Odonata), predaceous diving beetle small or unavailable because of water larvae (Coleoptera), water boatmen depth. During springs with little surface (Corixidae), mosquito larvae (Culicidae), runoff, the availability of this food ap and midge larvae (Chironomidae) were peared to be limited or reduced. Krapu the insects most often eaten. Midge (1974a) reported that earthworms did not larvae were the insects most often con occur in the diet of pintails during 1971 sumed by blue-winged teals, gadwalls, when precipitation was low during April. and pintails. This insect contains nutri Plant matter accounted for 27% of the tionally valuable ingredients for breed diet of laying female gad walls feeding ing females (Krapu and Swanson 1975) in saline lakes and 25% of those that fed and ducklings (Sugden 1973). in freshwater wetlands. Although the Crustaceans were major food items volumes were similar, the species of taken by shovelers (54%) and gadwalls plant and animal foods differed. Fila (20 and 32%). They accounted for 14% of mentous algae made up 22% of the plant the diet of blue-winged teals, 16% of the parts eaten by gadwalls that fed in saline diet of mallards, and 14% of the diet of lakes but only 9% of the plant parts eaten pintails. Fairy shrimp (Anostraca) that by those that fed in freshwater lakes. occupied temporary and seasonal wet Duckweed (Lemna spp.) accounted for
51 FOODS OF LAYING FEMALE DABBLING DUCKS
8%, pondweed (Potamogeton spp.) 4%, domesticated cereal grains. Their bill and bladderwort (Utricularia vulgaris) structure, however, is designed to effi 3% of the diet of female gad walls that fed ciently extract small food items in a on the fresher wetlands. water medium (Goodman and Fisher Mallards and pintails selected similar 1962). Birds observed feeding on tilled proportions of plant fru its, which ac wetlands that contained water usually counted for 27 and 23% of the diets, ate small fruits, such as those of barn respectively. In the food of other species, yard grass. Small fruits and inverte fruits accounted for 1% in laying blue brates often occurred in clusters within winged teals and shovelers, 1% in gad the esophagus, suggesting that several walls that fed in saline lakes, and 3% in are filtered and swallowed as a unit. gadwalls that fed in freshwater wetlands. Small fruits were never abundant in the Mallards and pintails often fed in tilled esophagus of birds that fed in the upland, ephemeral wetlands located in cropland. suggesting that feeding is most efficient The most abundant fruit in their diet was in the upland when confined primarily barnyard grass (Echinochloa crusgalli), to relatively large fruits that are abun which accounted for 15% of the food of dant because of a particular agricultural mallards and 8% of that of laying pintails. practice. Barnyard grass formed 71% of the diet of Food selection by various species is pintail hens that fed on tilled wetlands influenced by the ability to physically (Krapu 1974b). process food items of different textures. Gadwalls, for example, have a large Factors Influencing Food Selection muscular gizzard and select fine sand for grit, which is used to process plant Food selection by breeding females tissues such as filamentous algae. This during egg formation was influenced by species did not select snails, even when bird morphology, nesting chronology, they were abundant at feeding sites, and invertebrate behavior, and the species the few that were eaten were a species structure of the aquatic biota, which was with a thin shell. Parts of heavy shelled in turn determined by current and past snails are retained as grit in the gizzards hydrological conditions. of blue-winged teals and often replace Morphological characteristics deter coarse sand used as grit. Perhaps gad mine the capacity of each species to walls avoid coarse shelled snails because efficiently extract food items from the they interfere with the grinding action wetland environment. Spacing of the that is required to process plant tissues. lamellae on the bill, for example, deter Little is known about the relation mines the minimum size of aquatic between morphological characteristics organisms that can be filtered efficiently, and food selection. Only some of the Shovelers have fine lamellae and feed more obvious differences have been men principally on microcrustacea. Neck tioned here, but their influence appears length and body size determine maxi to be significant. mum feeding depths that can be reached Nesting chronology varies markedly to use food items in the mud-water inter among species of dabbling ducks, and face. For example, mallards and pintails thereby influences food selection during can feed at greater depths by tipping the laying period. A. T. Klett (personal than can blue-winged teals. communication) examined 1976 nest Certain species of dabbling ducks, initiations of 224 blue-winged teals, 135 particularly the mallard, pintail, and mallards, 57 pintails, 56 gad walls, and 50 gadwall, have adapted to feeding on shovelers on a study area adjacent to
52 WATERFOWL AND WETLANDS SYMPOSIUM
Interstate 94 in south central North dant or are forced to concentrate on the Dakota. Pintails and mallards started surface by unfavorable chemical condi nesting in early April, and 50% of the tions. Certain aquatic invertebrates are starts were before 3 and 8 May, respec made available to ducks when they are tively. Shovelers started their first nests concentrated by wind action. The role of in mid-April and 50% were started by invertebrate behavior in the selection of 10 May. The first blue-winged teal nest food by waterfowl was discussed by was found on 26 April and 50% of the Swanson and Sargeant (1972), Swanson nests of this species were initiated by et al. (1974), Serie and Swanson (1976), 15 May. Gadwalls started nesting in mid and Swanson (1977). May and 50% had started before 29 May. When invertebrates become highly Differences in nesting chronology reduce available, as during an insect emergence overlap in the use of food resources. or from a population buildup, morpho Breeding females of each species tend to logical differences that influence food use a different hydrological phase within selection no longer are a dominant factor the wetland complex, and the hydrology influencing feeding efficiency, and of prairie wetlands changes as the season several species may consume the same progresses. Food availability, a major type of food item. For example, when factor influencing food selection, changes Daphnia pulex or D. magna populations in response to phenological and hydro are unusually dense, all species of prairie logical conditions. Renesting attempts, nesting dabbling ducks can effectively which are determined by the magnitude feed on the large adults. As the popula of nest destruction on one hand and wet tion declines and availability of large land quality on the other, also influence adults is reduced, only shovelers can food selection by extending the laying continue to feed efficiently on the re period. Blue-winged teals held on experi maining small individuals. mental ponds at the Northern Prairie Wildlife Research Center produced up to five clutches of eggs (Swanson and Meyer The Wetland Complex 1977) after imposed nest destruction. The renesting effort appears to be strong in Invertebrate species structure, popula years when abundant surface water is tion densities, and behavioral charac present in late spring. teristics change rapidly within the Feeding behavior is a function of inter wetland complex during annual, sea actions among food availability, mor sonal, and 24-hour periods (Swanson et phological adaptations, and physiological al. 1974, Swanson 1977); food availability condition. Consumption occurs when fluctuates accordingly. A mallard nest invertebrates are eaten when they move ing in early April is influenced by a into zones where they are available to different water regime and invertebrate feed ing waterfowl; nighttime feeding population than is a gadwall that nests in may occur when the availability of inver late May. Water regimes also change te brates increases between sunset and with each renesting attempt. Pintail sunrise. This occurs, for example, when hens, for example, feed principally on aquatic insects such as mayflies (Ephern fairy shrimp and earthworms in early eroptera) or midges emerge, or when spring (Krapu 1974a), whereas renesting beetle or mosquito larvae come to the hens feed primarily on midge larvae surface to maintain or replenish their (Krapu 1974b). oxygen supply. Crustaceans are con Wetland classes within the complex sumed when they are unusually abun are unique in terms of the biotic com
53 FOODS OF LAYING FEMALE DABBLING DUCKS
munities that are produced and the is usually reduced. The hydrological seasonal succession that occurs in the conditions within the wetland complex invertebrate community (Swanson et al. determine the foods that will be available 1974). Invertebrate and plant composi to breeding ducks during a given period. tion may change from one year to the Different foods were selected by blue next within a wetland if a major change winged teals during a wet period, when occurs in hydrology brought about by many seasonal wetlands contained drought conditions. A seasonal hydrolog water, than during a dry year when few ical succession occurs among different were flooded. During wet periods snails classes of wetlands within a complex, were a predominant blue-winged teal providing highly available plant and food on seasonal wetlands, whereas animal foods that support a variety of during years when seasonal wetlands waterfowl species throughout the nest were dry the birds fed principally on ing, renesting, and brood rearing period. chironomid larvae in semipermanent and Mallards and pintails begin their first permanent lakes in drawdown. Food nests in early spring, when most of the selection by pintail hens during the foods associated with semipermanent breeding season also has been shown to lakes are isolated at depths unavailable be influenced markedly by water condi to dabbling ducks and ice still covers tions (Krapu 1974a). many permanent lakes. Ephemeral and temporary wetlands receive high use at Feeding Niche. this time. As the season progresses, seasonal wetlands become the major The feeding niche occupied by a given source of food used by rene sting mallards species varies with season and is in and pintails, and shovelers and blue fluenced by the physiological demands winged teals are starting their first nest. and reproductive condition of the bird. By late spring, water levels begin to Many interacting factors influence food recede on semipermanent wetlands, selection and make it difficult to define aquatic insects start to emerge, and sub the feeding niche of each species. The merged aquatic plants extend to the dynamic water regime of the prairies, in water surface and provide a substrate association with a high incidence of re for invertebrates. Certain semiperma nesting, tends to mask species dif nent wetlands provide an abundant and ferences. Also, the high incidence of highly available food supply by late invertebrates in the diet of laying spring and early summer. At this time females places this segment of the breed gadwalls are starting their first nests, ing population in a unique category. and renesting dabbling ducks of other Large sample sizes would further species are obtaining food from semi delineate food selection; however, it is permanent lakes. Semipermanent wet difficult to obtain large numbers of lay lands also provide food for ducklings. ing females because of the number of Wetland hydrology is highly variable females that must be collected to supply from year to year, and normal patterns a small number that are laying. may reverse in drought years. During the Food data have indicated some obvious early springs of 1973 and 1977, tempo differences in feeding niches, although rary and seasonal wetlands were dry, some overlap occurs. Shovelers tend to and dabbling ducks fed on semiperma select small crustaceans. Consumption nent lakes as water levels receded of snails by shovelers was similar in (Swanson and Meyer 1977). When early volume to that by blue-winged teals but drawdown occurs, waterfowl production consisted of a greater proportion of small
54 WATERFOWL AND WETLANDS SYMPOSIUM
planorbid species. Gadwalls were similar quality wetland habitats produce an to shovelers in their use of crustaceans abundant supply of highly available but differed from all other species in small aquatic animals during the nesting their avoidance of snails and greater use and brood rearing period. Quality aqua of vegetation, particularly filamentous tic habitat is particularly critical when algae. Gadwalls selected similar types of nest predators destroy a large percentage foods even though feeding on wetlands of the nests, forcing hens to renest after that provided different species of plants their body reserves already have been and invertebrates. Mallards and pintails expended in previous attempts. A single differed from the other three species by hen may lay up to five clutches of eggs consuming fruits. Foods of these two before a successful hatch is achieved or species were somewhat similar, and dif she terminates her nesting efforts for the ferences reflected in the data may be year. It is important, therefore, that attributed to sample size. The study of abundant high quality food be available mallard feeding ecology is incomplete on the breeding grounds throughout the and greater differences may be detected nesting period. The prairie wetland com in the fu ture. The mallard is more ver plex with all of its wetland classes is an satile, selecting foods available in several important habitat component in the wetland classes, and this characteristic ecology of prairie dabbling ducks, and may be found to be a factor in niche wetland complexes should be stressed in separation. the preservation of waterfowl production habitat. Land-use practices on the prai CONCLUSIONS ries have favored drainage of shallow, non-permanent wetlands into drainage Female anatids that are producing systems or into wetlands located at lower eggs consume a high proportion (greater elevations. This practice is altering the than 70%) of small invertebrates (insects, natural wetland complex of the prairies, snails, and crustacea). Their ability to creating larger and more permanent obtain these foods during the nesting lakes that are less attractive to breeding period depends largely on the types of dabbling ducks (Swanson and Meyer aquatic habitat that are available. High 1977).
55 FOODS OF LAYING FEMALE DABBLING nUCKS
LITERATURE CITED
BARTONEK, J. C. 1968. Summer foods and Manage. 41(1) :118-127. feeding habits of diving ducks in Mani MARTIN, A. C., AND F. M. UHLER. 1939. toba. Ph.D. Thesis. Univ. of Wisconsin,' Food of game ducks in the United States Madison. 113pp. and Canada. U. S. Dept. Agric. Tech. Bul!. ___ . 1972. Summer foods of American 634. 156pp. widgeon, mallards, and a green-winged MOYLE, J. B. 1961. Aquatic invertebrates teal near Great Slave Lake, N.W.T. Can. as related to larger water plants and Field-Nat. 86(4): 373-376. waterfow!. Minnesota Dept. Conserv. ___ , AND J. J. HICKEY. 1969. Food Invest. Rep. 2:33. 24pp. habits of canvasbacks, redheads, and PERRET, N. G. 1962. The spring and summer lesser scaup in Manitoba. Condor 71(3) : foods of the common mallard (Anas 280-290. pluturh.uncho« platyrhynchos L.) in south ___ , AND H. W. MURDY. 1970. Sum central Manitoba. M. S. Thesis. Univ. of mer foods of lesser scaup in su barctic British Columbia, Vancouver. 82pp. taiga. Arctic 23(1): 35-44. ROGERS, J. P., AND L. J. KORSCHGEN. DILLON, O. W., JR. 1958. Food habits of 1966. Foods of lesser scaups on breeding, wild ducks in the rice-marsh transition migration, and wintering areas. J. Wild!. area of Louisiana. Proc. Southeastern Manage. 30(2) :258-264. Assoc. Game and Fish Commissioners SERlE, J. R., AND G. A. SWANSON. 1976. 11:114-119. Feeding ecology of breeding gad walls on DIRSCHL, H. J. 1969. Foods of lesser scaup saline wetlands. J. Wild!. Manage. 40(1) : and blue-winged teal in the Saskatchewan 69-81. River Delta. J. Wild!. Manage. 33(1) :77 SLOAN, C. E. 1972. Ground-water hydrology 87. of prairie potholes in North Dakota. U.S. EISENLOHR, W. S. 1972. Hydrologic inves Geo!. Surv. Prof. Pap. 585-C. 28pp. tigations of prairie potholes in North STEWART, R. E. 1962. Waterfowl popula Dakota, 1959-68. U.S. Geo!. Surv. Prof. tions in the Upper Chesapeake Region. Pap. 585-A. 102pp. U.S. Fish Wild!. Servo Spec. Sci. Rep. GOODMAN, D. C., AND H. I. FISHER. 1962. Wild!. 65. 208pp. Functional anatomy of the feeding , AND H. A. KANTRUD. 1971. apparatus in waterfowl (Aves: Anatidac). Classification of natural ponds and lakes Southern Illinois University Press, Car in the glaciated prairie region. U. S. Fish bondale. 193pp. Wild!. Servo Resour. Pub!. 92. 57pp. KANTRUD, H. A., AND R. E. STEWART. ___ , AND . 1972. Vegetation 1977. Use of natural basin wetlands bv of prairie potholes, North Dakota, in breeding waterfowl in North Dakot~. relation to quality of water and other J. Wild!. Manage. 41(2) :243-253. environmental factors. U.S. Geo!. Surv. KRAPU, G. L. 1974a. Feeding ecology of pin Prof. Pap. 585-D. 36pp. tail hens during reproduction. Auk 91(2) : 278-290. SUGDEN, L. G. 1973. Feeding ecology of pin ___ . 1974b. Foods of breeding pintails tail, gadwall, American widgeon and les in North Dakota. J. Wild!. Manage. 38(3) : ser scaup ducklings in southern Alberta. 408-417. Can. Wild!. Servo Rep. Ser. 24. 45pp. , AND G. A. SWANSON. 1975. SWANSON, G. A. 1977. Diel food selection Some nutritional aspects of reproduction by Anatinae on a waste stabilization in prairie nesting pintails. J. Wild!. system. J. Wild!. Manage. 41(2) :226-231. Manage. 39(1) :156-162. ___ , AND J. C. BARTONEK. 1970. Bias LANDERS, J. L., T. T. FENDLEY, AND associated with food analysis in gizzards A. S. JOHNSON. 1977. Feeding ecologv of blue-winged tea!' J. Wild!. Manage. of wood ducks in South Carolina. J. Wild!. 34(4): 739-746.
56 WATERFOWL AND WETLANDS SYMPOSIUM
___ . AND M. 1. MEYER. 1977. Impact waterfowl breeding habitat. Pages 65-71 of fluctuating water levels on feeding in E. Schneberger. ed. A symposium on ecology of breeding blue-winged tea!. J. the management of midwestern winter Wildl. Manage. 41(3) :426-433. kill lakes. N. Cent. Div. Am. Fish. Soc. ___ . , AND J. R. SERlE. 1974. Spec. Pub!. Feeding ecology of breeding blue-winged • AND A. B. SARGEANT. 1972. teals. J. Wild!. Manage. 38(3):396-407. Observation of nighttime feeding behav ___ . AND H. K. NELSON. 1970. Poten ior of ducks. J. Wild!. Manage. 36(3): 959 tial influence of fish rearing programs on 961.
57 ~ \ WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Symp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
NUTRITION OFFEMALE DABBLING DUCKS DURING REPRODUCTION
GARY L. KRAPU
U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401
Abstract: Females of wild populations of prairie nesting dabbling ducks select diets that contain relatively high levels of animal protein and calcium during the period of egg formation. Experi mental studies 1 conducted at the Northern Prairie Wildlife Research Center in 1975 and 1976 indicate that mallard (Anas platyrhllnchos) reproduction is adversely affected when hen access to animal matter is curtailed. Hens on a wheat (Triticum aestivum) diet laid 46 and 50% fewer eggs than did hens on a control diet during the 1975and 1976 nesting seasons, respectively. The addition of 10 g of live earthworms (Lumbricus sp.) daily to the wheat diet throughout the nest ing season markedly improved egg hatchability but egg production remained low, presumably because of a deficiency of total protein or one or more essential amino acids. Hens consuming wheat during the laying of a clutch failed to ovulate an average of 1 day for every 2 eggs laid, whereas hens on the control diet skipped ovulation 1 day for every 4.6 eggs. Mean weights of eggs laid by hens fed the wheat diet during 1975 and 1976were 12 and 7% less, respectively, than those laid by the control groups. Food deprivation imposed by removal of the control diet for a 3-day period during the laying of each clutch resulted in 45% fewer eggs being laid during the nesting season than among controls fed ad libitum; egg and yolk weights remained similar. Yolks (dry) from eggs produced by hens on control and wheat treatments weighed 11.9 ± 1.3 g and 10.2 ± 1.1 g (mean ± SD), respectively. Mallard ducklings without access to food upon hatching survived longer when hatched from larger eggs. Calcium required for egg formation apparently is derived primarily from the diet during the nesting season. The information pre sented in this paper underscores the important role of nutrition in determining reproductive potential in dabbling ducks.
The nutrient requirements of free-liv ment in nutrition research on free-living ing populations of dabbling ducks have populations of breeding waterfowl re received limited attention in the scienti quires access to information on food fic literature. This dearth of information habits, reproductive physiology, and has resulted, in part, because advance- several other aspects of breeding biology.
59 NUTRITION OF FEMALE DABBLING DUCKS
Knowledge of wetland ecology, and in mental data those nutrients most likely particular those factors controlling to be limiting to reproduction. A paucity waterfowl food abundance, are also of published information on dabbling important when nutrient effects on duck nutrition has led me to draw fre reproductive potential in dabbling ducks quently upon relevant literature on other are considered. Detailed information on groups of birds. In conclusion, I will dis food habits and wetland ecology on the cuss dabbling duck nutrition in relation breeding grounds has only recently be to wetland ecology in the Prairie Pothole come available. Region. Studies of free-living populations of I thank D. G. Jorde, S. Stewart, and birds during the past decade have shown J. A. Shoesmith for their assistance in food selection is influenced by chemical collection of certain data presented in and nutrient composition. Gardarsson this paper; V. A. Adomaitis for super and Moss (1970:66) reported that Ice vising certain chemical analyses; F. B. landic ptarmigan (Lagopus mutus) selec Lee for supervising rearing of experi tively fed upon the most nutritious foods mental birds; D. H. Johnson for sugges available during the breeding period. tions concerning experimental design; Moss (1972:424) reported that selection and E. Multer for assistance in literature for nitrogen and phosphorus by red review. For critical review of this manu grouse (Lagopus lagopus scoticus) in script, I thank D. H. Johnson, M. W. creased from winter to spring, whereas Weller, and W. R. Goforth. that for calcium, soluble carbohydrates, and crude fat did not. Food selection has METHODS been found to change markedly during the breeding period among certain spe Experimental findings that are pre cies of waterfowl. Pintails (Anas acuta) sented in this paper were obtained with feed primarily on plant foods for most of captive mallards reared from eggs of the year but select greater quantities of wild origin gathered in south central animal foods during the breeding season, North Dakota during June 1974. Birds particularly during the period of egg for were propagated at the Center and re mation (Krapu 1974). Feeding ecology search was conducted during April-June studies of gad walls (A. strepera) (Serie 1975and 1976. and Swanson 1976), black ducks (A. rub Treatments were designed to test ripes) (Reinecke 1977), mallards (Swan effects of diet quality and availability on son et al. 1979), and wood ducks (Aix egg production, egg and yolk weight, and sponsa) (Drobney 1977) have also shown egg hatchability. In 1975, treatment increased consumption of animal matter effects on egg production, egg weight, during the laying period. Among adult and yolk weight were studied, whereas breeding hens, nutrient intake must be in 1976the effects of diets on egg produc sufficient to meet energy requirements, tion, egg weight, and hatchability were replace body constituents lost during evaluated. Potential genetically induced normal body processes, and provide the differences among teatments were mini nutrients necessary to produce viable mized by a stratified random selection clutches of eggs. procedure whereby paired comparisons The primary purpose of the present of treatment effects were made among paper is to describe nutrient selection brood mates. Testing was conducted in during the breeding period in certain outdoor breeding pens situated in an species of prairie-nesting dabbling ducks open field on the Center grounds to mini and to attempt to identify from experi mize man-induced disturbance. Control
60 WATERFOWL AND WETLANDS SYMPOSIUM
and wheat diets during both years of the beam balance. In 1975, the yolk of each study were provided ad libitum. Protein egg laid was separated from other egg content in the control and wheat diets constituents in the laboratory and placed was 29 and 14%, respectively. Food was in a sealed and labeled plastic vial and removed from pairs on the restricted stored at -20 C until removed for drying. control diet on the afternoon following Yolks were dried in a controlled forced the laying of the third egg of a clutch; convection oven until reaching constant the food was returned 72 h later. Pairs weight (48 h). Egg yolks were dried whole on the three treatments during each year for 24 h and separated into quarters for received oystershells fed ad libitum. the remaining period. Dry yolks were In 1976, earthworms were fed with weighed on a Mettler balance to 0.1 g. In wheat as one treatment. Each hen on the 1976, fertile eggs were incu bated to wheat plus earthworm diet received 10 g determine hatchability. live earthworms daily which were weighed on a triple beam balance to the RESULTS AND DISCUSSION nearest 0.1 g. Earthworms were placed into a water-filled glass pan in selected Nutrient Selection breeding pens after a partition had been lowered temporarily separating the During the period of egg formation drake and hen to insure that the hen dabbling duck hens ingest diets that are received the full daily earthworm ration. principally animal matter (Table 1). A plastic floor cover prevented soil inver From the nutritional standpoint, laying tebrates or other plant and animal mat pintail, mallard, and gadwall hens are ter from becoming available to the pairs. selecting a diet that contains about 28% Pen nest boxes were checked daily to protein, whereas blue-winged teals (A nas label eggs laid on that date and to docu discors) and shovelers (A. clypeata) con ment laying patterns. Eggs were re sume a somewhat higher protein level. moved on the third day after completion Selection of animal matter during egg of the clutch; each egg was cleaned and formation seems largely independent of weighed to the nearest 0.1 g on a triple the level of availability of plant foods. Table 1. Percentage of major types of foods consumed by hens of certain species of wild dabbling ducks during the laying period in North Dakota. Data are based upon volumetricmeasurements ofesophagealcontents. Foodtype Percent Mol- Armel- Crus- In- Plant Species lusca ida tacea secta Seeds parts Animal Plant Source Mallard 14 26 16 14 27 3 70 30 Swanson et al. (1979) Pintail 15 11 14 37 23 tr a 77 23 Krapu (1974) Gadwall 20 52 1 27 72 28 Serie and (saline) Swanson (1976) Gadwall 4 tr 32 36 3 25 72 28 Swanson et (fresh) al. (1979) Shoveler 40 54 5 1 tr 99 1 Swansonet al. (1979) Blue-winged 40 1 14 44 1 99 Swansonet teal al. (1974) a Trace.
61 NUTRITION OF FEMALE DABBLING DUCKS
However, the specific types of animal feed on crustaceans but consume few and plant matter in the diet are strongly snails (Table 1). Snails and certain crus influenced by their level of availability. taceans appear to be the principal Pintails and mallards, for example, shift sources of calcium in the diets of prairie to animal foods irrespective of access to nesting dabbling duck hens plus being cereal grains even though these grains important sources of protein. are preferred foods during much of the Scott (1973:49) indicated that captive year. breeding ducks and geese should receive Most invertebrates consumed by dab 0.5% available phosphorus in diets when bling ducks are primarily protein on a fed. ad libitum. Most plant and animal dry-weight basis (Table 2). Amino acid foods appear to contain adequate levels composition of certain of these inverte of phosphorus (Table 2). Wild breeding brates compares favorably with egg pro ducks may require higher concentrations tein (Krapu and Swanson 1975). This is of key nutrients than is considered ade an important consideration, because the quate in prepared diets, however, be biological value of protein is high only if cause of restricted access to foods. all essential amino acids are contained in Most plant foods consumed by dab a proper ratio to the protein being bling ducks are primarily carbohydrate formed (Scott et al. 1969:57). (NFE), contain relatively low levels of Among invertebrate foods, calcium is protein (Table 2), and have low concen most concentrated in the calcareous exo trations of certain essential amino acids skeletons of snails. Snails are a major required for egg formation (Krapu and food in the diet of most prairie-nesting Swanson 1975). Seeds of aquatic and ter dabbling ducks except gad walls, which restrial plants comprise the bulk of the
Table 2. Nutrient composition of certain plant and animal foods consumed by female dabbling ducks breeding in the Prairie Pothole Region. __~~ ~F~o~o~d-!"it~e~m~____ % nutrient composition (dry) Scientific name Common name Protem Fat NFE Fiber Ca P Plant Cliulophoroceaer Green algae 16.0 0.2 41.3 22.4 2.9 0.6 Glyceriagrarulisa Mannagrass (caryopses) 6.0 1.4 76.1 7.9 0.3 0.5 Scolochloajestucaceab Whitetop (caryopses) 8.8 1.9 67.9 16.1 0.4 0.4 Triticum aestivumb Wheat (grains) 18.2 1.7 75.8 2.4 <: 0.03 0.6 Echinochloacrusgalli b Barnyard grass (grains) 14.2 0.5 46.6 31.3 <: 0.05 0.6 Beckmannia syzigl1£hnea Sloughgrass (caryopses) 7.0 6.5 59.6 20,0 0.5 0.4
Animal Oligocbaetal' Earthworms 60.2 7.7 12.3 0.4 0.2 1.0 Anostraca b Fairy shrimp 71.9 8.6 1.5 3.9 0.3 1.4 Cladocera a Waterfleas 31.8 1.5 10.9 7.3 11.8 1.2 Amphipodaj' Scuds 47.0 5.9 16.5 8.4 Diptera b Midges (larvae) 66.4 5.8 14.9 0.5 1.3 Gastropoda b Snails (without shell) 58.9 0.1 21.9 0.7 4.2 0.9 Gastropoda a Snails (with shell) 16.9 0.7 5.8 12.4 26.1 0.3 aSugden (1973). bKrapu and Swanson (1975).
62 WATERFOWL AND WETLANDS SYMPOSIUM
plant matter consumed by most species, free-living populations, lengthening of gad walls being an exception (Table 1). the period required to complete the clutch because of marginal food re Effect. of Nutrition on Reproduction sources increases the probability of nest destruction. To obtain a better understanding of Lipids stored in the yolk are of critical the underlying basis for selection of ani importance to developing embryos and mal matter by dabbling duck hens during newly hatched ducklings. However, lipid the period of egg formation, I conducted needs from the diet are small, because experiments with mallards to test hens can either synthesize most lipids dietary effects on egg production, egg from other nutrient sources or can draw and yolk weight, and egg hatchability. upon lipid reserves, particularly early in The results of these studies are examined the nesting season. Lipid reserves, pri in this section. marily in subcutaneous and visceral fat Egg Production. - The number of eggs depots, are substantial in prenesting laid by mallard hens during the nesting mallards and pintails and contribute season varied directly with the quality of significantly to the lipid requirements their diet. Hens fed wheat (14% protein) needed to form the initial clutch (G. L. plus supplemental calcium averaged 46 Krapu, unpublished data). Whether and 50% fewer eggs during the nesting stored lipids become yolk or are expended season than did controls on a 29% protein as energy for feeding and/or other breed diet (Tables 3, 4). In addition, mallard ing needs, these reserves lessen nutrient hens under the stress of a low protein stress during nesting. plant diet ovulated at irregular intervals Calcium for egg production apparently when laying. For example, hens fed the is obtained principally from food re plant diet while laying a clutch averaged sources available at the time of breeding. 1 day skipped per every 2 eggs laid, Calcium content in femurs from wild whereas hens on the animal diet failed to mallard hens I sampled increased during ovulate 1 day for every 4.6 eggs laid. The the month following hen arrival on the latter rate of missed ovulations ap breeding grounds (Fig. 1). This seems proaches that which I have observed in reasonable, because the diet of wild mal field environments. Skipping of days lards is low in calcium during the winter between eggs by mallard hens presum in Louisiana (Junca et al. 1962). Comar ably was caused by inadequate access to and Driggers (1979) used 45calcium to total protein or certain essential amino trace the origin of calcium in chicken acids. Scott (1973) noted that if a severe eggshell and estimated that 60-75% was deficiency of one or more essential amino ingested and the remainder came from acids develops, egg production will cease. body stores. Scott (1973) stated that the From the standpoint of productivity in calcium in medullary bone is sufficient
Table 3. Egg production, egg weight, and yolk weight (mean ± SD) among mallard pairs on selected treatments at the Northern Prairie Wildlife Research Center, James town, North Dakota, in 1975. Treatment No. pairs No. eggs/pr Egg wt Yolk wt (g) (g) Control 10 31.2± 6.1 55.9±4.3 1l.9±1.3 Restricted control 7 17.3±9.2 55.6±4.0 11.9± 1.2 Wheat 10 16.7±4.4 49.0±3.9 10.2± 1.1
63 NUTRITION OF FEMALE DABBLING DUCKS
Table 4. Egg production and egg weight (mean ± SD) and hatchability rate among mallard pairs on selected treatments at the Northern Prairie Wildlife Research Center, Jamestown, North Dakota, in 1976. Treatment No. pairs No. eggs/pr Eggwt Hatchability (g) rate (%) Control 8 22.6±7.7 55.8±4.0 70.7 Wheat 7 12.4±3.6 51.7±4.8 41.0 Wheat + earthworms 7 11.3±8.3 52.3+4.6 67.9 for 2 or 3 eggs and recommended that ments are abundant on the soil surface prepared diets for breeding ducks and of seasonal and semi-permanent wet geese contain 2.7% calcium. Egg produc lands in the Prairie Pothole Region, so tion in birds is affected when a calcium calcium is not likely to be a limiting fac deficiency exists. Ring-necked pheasant tor in the diets of breeding dabbling (Phasianus colchicus) hens, when fed ducks that feed upon snails. diets with marginal concentrations of A stable source of high quality foods is calcium (0.4-1.1% of the diet) during the needed during the nesting season to breeding period, produced eggs at a much maintain high levels of egg production. lower rate than hens fed diets containing In experimental studies, a 72-h with 2.0 to 3.2% (Greeley 1962, Chambers et drawal of the control diet from mallard al. 1966, Hinkson et al. 1970).Grau (1968) hens during each laying cycle resulted in noted that most mineral deficiencies a 45% decline in total number of eggs laid result in cessation of egg laying rather during the nesting season but did not than in production of eggs that are defi affect egg size or yolk content (Table 3). cient in minerals. Snail shells and frag Breitenbach et al. (1963) reported that
42 39 • &l S 360 • 330 ~ • ::::> 300 • • U .... 270
120 10 20 30 10 20 30 10 20 30 APRIL MAY JUNE
Fig. 1. Calcium content in femurs of 26 mallard hens breeding in North Dakota, by date of collection during 1974-1976(G. L. Krapu, unpublished data).
64 WATERFOWL AND WETLANDS SYMPOSIUM
ring-necked pheasant hens fed at mini-' nants (Scott et al. 1969:16). Fisher (1972: mum requirements during the breeding 433) noted that birds eat to satisfy two season laid only 9% as many eggs as were basic needs: the physiological demands of laid by controls fed ad libitum. Ivy and the body and food volume needed to Gleaves (1976) reported that level of egg reach satiety. If satiety is fulfilled production had an effect (P< 0.01) on through bulkiness of the diet the bird consumption of food, protein, and energy will stop eating before the physiological in chickens. needs are satisfied. In studies of blue Selection of invertebrates, particularly winged teals, invertebrates were digested larval forms without chitinous exoskele within minutes, whereas plant foods tons, provides an advantage over a plant either required several hours to break diet during egg production because of the down or were passed through the diges higher concentration of required nu tive system intact (Swanson and Bar trients in animal foods and more rapid tonek 1970). digestion. Chitin, which forms the struc Egg and Yolk Weights. - My findings tural material of the exoskeleton of many indicate diet quality affects egg weight adult insects, is indigestible in non-rumi- in the mallard. Eggs produced by hens
50
40
30 WHEAT
20
(J) o 10 o w LL 0 I Z w 50 U a: w a.. 40
30 CONTROL
20
10
c c o o o o o "f>' ,,«) ,,'0 ",0",'1.- ",f> "'«) -, -,: -, -, -, -, -, ,,'1.- "f> ,,'" ,,'0 ",0 ",'1.- rJ' EGG WT (91 Fig. 2. Mallard egg weight distribution in relation to dietary treatment during 1975and 1976.
65 NUTRITION OF FEMALE DABBLING DUCKS
consuming a diet with 29% protein (ap and/or slow digestion rate caused by a proximate level of protein in natural high fiber content. diet) were 12% heavier in 1975 and 7% Relationship of Egg Weight to Duck heavier in 1976 than eggs laid by hens fed ling Survival. - Level of stored nutrient a 14% protein plant diet (wheat) supple reserves in yolks of dabbling duck eggs mented with calcium (P <0.001, Tables 3, affects length of time newly hatched 4). Egg weight distribution by treatment ducklings can survive when food is scarce, is shown in Fig. 2. Scott (1973) observed In experimental tests, newly hatched that when the supply of one or more es mallard ducklings were provided only sential amino acids is deficient, the water in a controlled environment. Ten quantity of protein synthesized may be ducklings from large eggs (:> 47 g) sur decreased, causing a reduction in egg vived 149.5 h, whereas 6 ducklings from size. The level of the essential amino acid small eggs «45 g) survived 116.8 h methionine in the diet of chickens has (G. L. Krapu, unpublished data). Re been shown to affect egg weight (Leong search findings presented in this paper and McGinnis 1952). Concentration of suggest the quality of food resources methionine is frequently low in plant available to breeding hens at nesting can foods. Although egg size decreases with a have a significant effect on nutrient reduction in dietary levels of individual reserves available to ducklings at hatch essential amino acids or of total protein, ing. Newly hatched wild ducklings must the concentration of amino acids among often travel long distances to reach water eggs that are produced is not reduced areas with adequate food resources, and significantly in chickens (Ingram et al. access to yolk nutrient reserves reduces 1950). nutrient stress during that period. Yolk weights of mallard eggs laid by hens on the plant diet diminished with Egg Hatchamlity. - Diet quality in the decline in egg size. Mean yolk weight fluenced hatchability rate of eggs laid by (dry) was 14% less (11.9±1.3to 10.2±1.1g) mallard hens (Table 4). Selection of some on the plant diet than on the control diet animal matter by laying hens appears (Table 3); this is a potential mean loss in necessary solely in view of the deleteri energy reserves of about 13.8 kcal to ous effects on egg viability associated developing embryos and newly hatched with selection of plant diets. For ex young. High fiber content, which is ample, when 10 g of live earthworms characteristic of many plant foods con were added daily to the wheat diet of sumed by dabbling ducks (Table 2), can each hen, total egg production and egg affect egg and yolk weights. Menge et al. size remained similar to the wheat treat (1974) reported that when powdered cel ment, but hatchability rate increased lulose formed 15% of the diet of chickens, markedly (Table 4). Apparently the addi adverse effects on egg and yolk weight tion of the animal matter was adequate resulted. Turk and Barnett (1971) re to maintain hatchability rates but was ported that the addition of 15% oat inadequate to significantly change the (Avena sativa) hulls to the diet reduced level of egg production. Holm and Scott egg weight in chickens. Limited intake of (1954) reported that hatchability of fer natural plant foods during egg forma tile eggs laid by mallard hens fed an ex tion, including those containing rela perimental diet with 17% protein was tively high levels of cellulose, probably markedly lower than among eggs laid by has evolved, in part, because plant foods hens on a 28% protein diet during the contain low concentrations of critical third and fourth weeks of laying. In nutrients required for egg production studies of pintails, Krapu and Swanson
66 WATERFOWL AND WETLANDS SYMPOSIUM
(1975) reported an extremely low hatch (animal matter) include: (1) calcium and ability rate among hens having access phosphorus levels, (2) other B-eomplex solely to a plant diet (wheat); addition of vitamins, particularly riboflavin, and calcium to the plant diet increased hatch (3) levels of the essential amino acids ability only slightly. lysine and methionine. Dabbling duck hens in captivity con tinue to lay but at a reduced rate when Relationship of Female Dabbling Duck fed a protein deficient plant diet, but I Nutrition to Prairie Wetlands have concluded that wild hens seldom produce clutches solely from plant diets. Protein and calcium requirements of I reached this conclusion from data on dabbling duck females during reproduc food selection by wild hens during the tion are met primarily by feeding on laying period (Table 1) and because aquatic invertebrates. Dabbling duck clutches of wild dabbling ducks charac access to invertebrates comes through teristically have high hatchability rates. foraging in flooded shallow wetland Free-living hens apparently have access habitat. During censuses in North to the small levels of animal matter Dakota on randomly selected quarter necessary to maintain high levels of sections during 1965 and 1967-69, Kant hatchability. Vitamin B12, though of cri rud and Stewart (1977) found that 60% of tical importance in the diet for egg the breeding dabbling duck pairs were on production and hatchability, is required seasonal wetlands. Each breeding pair in only minute quantities. Therefore, utilizes several shallow wetlands to ob when habitat conditions are poor and tain nutrient requirements. Radio invertebrates are present in low densi marked mallard hens used from 7 to 22 ties, nesting efforts are more likely to natural wetlands during the nesting terminate because of a deficiency in total season (Dwyer et al. 1979). protein or certain amino acids rather Annual recruitment in prairie dab than from a reduction in egg viability bling duck populations varies with the from a vitamin deficiency. status of water conditions during the Animal protein is not necessary to nesting season. A strong correlation maintain high hatchability rates when between number of ponds in July and diets can be supplemented with vitamins. size of the returning breeding population Cooper and Hughes (1974) have shown the following spring has been docu that hatchability of eggs produced by mented (Crissey 1969). Flooding of shal chickens fed diets with and without ani low basins creates microhabitats con mal matter (fish meal) were similar ducive to propagation of certain inverte when the vegetable diet was fortified brates that are rich sources of protein with a vitamin mixture containing Vita and calcium. Breeding by various species min B 12. A deficiency of several vitamins of prairie nesting dabbling ducks coin other than Vitamin B 12 can also cause cides with periods when these organisms lowered hatchability rates (Scott et al. are most accessible. The semi-arid cli 1969: 108-113), but most vitamins are mate has favored those breeding strate required in only minute amounts and are gies that permit utilization of nutrient present in foods of plant origin; Vitamin sources accessible in a usable form only B is an exception because it is of ani briefly; pintail and mallard use of earth mal origin. According to Scott et al. worms when available after flooding of (1969: 59), factors other than Vitamin temporary ponds is a prime example. B12 that account for the high superiority My findings indicate that the number of diets with animal protein sources and composition of eggs produced by a
67 NUTRITION OF FEMALE DABBLING DUCKS
mallard hen during the nesting season specific interactions with other pairs and varies with the quality and accessibility other disturbances that curtail feeding of food resources. Dabbling duck hens activity. Certain species are more are physiologically capable of renesting tolerant to crowding than are others and several times after initial nests are tolerance is affected by food abundance. destroyed if high quality foods are avail When adequate nutrients are not ac able at adequate levels. Pintails, mal quired despite prolonged feeding efforts, lards, blue-winged teals, gadwalls, and yolk deposition is inhibited, follicles shovelers are all known to renest (Sowls collapse, and yolk material is resorbed 1955). Radio-marked mallard hens moni from the follicles. Drought is a principal tored during the nesting season in south natural phenomenon leading to inhibi central North Dakota made up to four tion of laying and follicular atresia. The nesting attempts in a single season (G. L. effects of drought on reproduction in Krapu, unpublished data). Swanson and waterfowl can be severe, as reported in Meyer (1977)studied experimental ponds several studies (Salyer 1962, Rogers 1964, and reported that blue-winged teals laid Smith 1969), but females are long lived, four and five clutches of eggs when each hence populations are capable of with clutch was removed soon after comple standing several years of widespread tion. Because dabbling duck hens mobi reproductive failures resulting from ad lize a major part of stored nutrients verse climatic conditions. Man-induced during initial nesting efforts (G. L. changes in the environment that either Krapu, unpublished data), access to high reduce or contaminate food resources, quality foods is a particularly important however, pose a serious, long term threat factor governing the magnitude of re to reproduction in dabbling ducks. nesting efforts. Water level management in breeding marshes should include con sideration of practices that enhance hen access to those protein- and calcium-rich CONCLUSIONS foods sought during the nesting season, thereby adding to recruitment through Reproduction in dabbling ducks is increased rene sting activity. strongly influenced by the quality and' Nutrient stress caused by deteriora abundance of foods accessible to the tion of wetland habitat conditions or female from shallow wetlands. Selection other factors during the breeding season of a diet that is principally animal mat reduces nesting activity in dabbling ter during the laying period provides ducks. Securing adequate nutrients, par adequate levels of calcium, total protein, ticularly protein, for laying one or more and essential amino acids for egg produc clutches of eggs requires prolonged feed tion. Whereas my data suggest hens ing bouts as shown by the proportion of producing clutches require invertebrates the daily time budget devoted to feeding throughout the nesting season, access during the laying period by hens of is particularly important during renest various species of dabbling ducks: gad ing when stored nutrient reserves have walls, 75% (Dwyer 1975), shovelers, 57% been depleted. The need for ingestion of (Afton 1977), mallards, 55% (Dwyer et al. animal matter during the nesting period 1979), and blue-winged teals, 35% (Miller to meet nutritional requirements under 1976). Feeding time needed to secure scores the key importance of maintaining adequate nutrients to lay a clutch of eggs an adequate base of shallow wetland is affected by the quality, density, and habitat to sustain the desired popula size of available foods and level of intra tions of breeding dabbling ducks.
68 WATERFOWL AND WETLANDS SYMPOSIUM
LITERATURE CITED
AFTON, A. D. 1977. Aspects of reproductive ciency on laying hen pheasants. J. Wildl. behavior in the northern shoveler. M. S. Manage. 26(2): 186-193. Thesis. Univ. of Minnesota, St. Paul. HINKSON, R. S., JR., L. T. SMITH, AND 65pp. A. G. KESE. 1970. Calcium requirement BREITENBACH, R. P., C. L. NAGRA, AND of the breeding pheasant hen. J. Wildl. R.K. MEYER. 1963. Effect of limited Manage. 34(1): 160-165. food intake on cyclic annual changes in HOLM, E. R., AND M. L. SCOTT. 1954. ring-necked pheasant hens. J. Wildl. Studies on the nutrition of wild water Manage. 27(1): 24-36. fowl. New York Fish Game J. 1(2): 171 CHAMBERS, G. D., K. C. SADLER, AND 187. R. P. BREITENBACH. 1966. Effects of INGRAM, G. R., W. W. CRAVENS, C. A. dietary calcium levels on egg production ELVEHJEM, AND J. G. HALPIN. 1950. and bone structure of pheasants. J. Wildl. Relation of tryptophan and lysine to egg Manage. 30(1): 65-73. production, hatchability and composition COMAR, C. L., AND J. C. DRIGGERS. 1949. of the protein of hens' eggs. Poult. Sci. Secretion of radioactive calcium in the 29(6):793-803. hen's egg. Science 109(2829): 282. IVY, R. E., AND E. W. GLEAVES. 1976. COOPER, J. B., AND B. L. HUGHES. 1974. Effect of egg production level, dietary Vegetable diet with or without fish meal protein and energy on feed consumption and hatchability of chicken eggs. Poult. and nutrient requirements of laying hens. Sci. 53(5): 1849-1852. Poult. Sci. 55(6):2166-2171. CRISSEY, W. F. 1969. Prairie potholes from JUNCA, H. A., E. A. EPPS, AND L. L. GLAS a continental viewpoint. Pages 161-171 in GOW. 1962. A quantitative study of the Saskatoon wetlands seminar. Can. Wildl. nutrient content of food removed from ServoRep. Ser. 6. the crops of wild mallards in Louisiana. N. Am. Wildl. Conf. 27: 114-121. DROBNEY, R. D. 1977. The feeding ecology, KANTRUD, H. A., AND R. E. STEWART. nutrition, and reproductive bioenergetics 1977. Use of natural basin wetlands by of wood ducks. Ph. D. Thesis. Univ. of breeding waterfowl in North Dakota. J. Missouri, Columbia. 170pp. Wildl. Manage. 41(2): 243-253. DWYER, T. J. 1975. Time budget of breeding KRAPU, G. L. 1974. Feeding ecology of pin gad walls. Wilson Bull. 87(3): 335-343. tail hens during reproduction. Auk 91(2): __ , G. L. KRAPU, AND D. M. JANKE. 278-290. breeding mallards. J. Wildl. Manage. 43 __ , AND G. A. SWANSON. 1975. Some (2):526-531. nutritional aspects of reproduction in FISHER, H. 1972. The nutrition of birds. prairie nesting pintails. J. Wildl. Manage. Pages 431-469 in D. S. Farner and J. R. 39(1): 156-162. King, eds. Avian biology. Vol. II. Academ LEONG, K. C., AND J. McGINNIS. 1952. An ic Press, New York and London. estimate of the methionine requirement for egg production. Poult. Sci. 31(4): 692 GARDARSSON, A., AND R. MOSS. 1970. 695. Selection of food by Icelandic ptarmigan MENGE, H., L. H. LITTLEFIELD, L. T. in relation to its availability and nutritive FROBISH, AND B. T. WEINLAND. value. Pages 47-71 in A. Watson, ed. 1974. Effect of cellulose and cholesterol Animal populations in relation to their on blood and yolk lipids and reproductive food resources. Blackwell Scientific Pub efficiency of the hen. J. Nutr. 104(12): lications, Oxford and Edinburgh. 1554-1566. GRAU, C. R. 1968. Avian embryo nutrition. MILLER, K. J. 1976. Activity patterns, vocali Fed. Proc. 27(1): 185-192. zations, and site selection in nesting blue GREELEY, F. 1962. Effects of calcium defi winged teal. Wildfowl 27:33-43.
69 NUTRITION OF FEMALE DABBLING DUCKS
MOSS, R. 1972. Food selection by red grouse SMITH, A. G. 1969. Waterfowl-habitat rela (Laqopus laqopue scoticuslLath.]) in tionships on the Lousana, Alberta, water relation to chemical composition. J. fowl study area. Pages 116-122 in Saska Anim. Ecol. 41(2): 411-428. toon wetlands seminar. Can. Wildl. Servo REINECKE, K. J. 1977. The importance of Rep. Ser. 6. freshwater invertebrates and female SUGDEN, L. G. 1973. Feeding ecology of pin energy reserves for black ducks breeding tail, gadwall, American widgeon and les in Maine. Ph. D. Thesis. Univ. of Maine, ser scaup ducklings in southern Alberta. Orono. 113pp. Can. Wild\. ServoRep. Ser. 24. 45pp. ROGERS, J. P. 1964. Effect of drought on SWANSON, G. A., AND J. C. BARTONEK. reproduction of the lesser scaup. J. Wildl. 1970. Bias associated with food analysis Manage. 28(2): 213-222. in gizzards of blue-winged teal. J. Wildl. SALYER, J. W. 1962. Effects of drought and Manage. 34(4):739-746. land use on prairie nesting ducks. Trans. __ , G. L. KRAPU, AND J. R. SERlE. N. Am. Wildl. Nat. Resour. Conf. 27: 1979. Foods of laying female dabbling 69-79. ducks on the breeding grounds. Pages SCOTT, M. L. 1973. Nutrition in reproduction in T. A. Bookhout, ed. Waterfowl - direct effects and predictive functions. and wetlands - an integrated review. Pages 46-59 in D. S. Farner, ed. Breeding Proc. 1977 Symp., Madison, WI, N. Cent. biology of birds. National Academy of Sect., The Wildlife Society. Sciences, Washington, D. C. __ , AND M. 1. MEYER. 1977. Impact of fluctuating water levels on feeding eco __, M. C. NESHEIM, AND R. J. YOUNG. logy of breeding blue-winged teal. J. 1969. Nutrition of the chicken. M. L. Scott Wild\. Manage. 41(3): 426-433. and Associates, Ithaca, NY. 511pp. __ , M. 1. MEYER, AND J. R. SERlE. SERlE, J. R., AND G. A. SWANSON. 1976. 1974. Feeding ecology of breeding blue Feeding ecology of breeding gad walls on winged teals. J. Wildl. Manage. 38(3): saline wetlands. J. Wildl. Manage. 40(1): 396-407. 69-81. TURK, D. E., AND B. D. BARNETT. 1971. SOWLS, L. K. 1955. Prairie ducks. The Stack Cholesterol content of market eggs. Poult. pole Co., Harrisburg, PA. 193pp. Sci. 50(5): 1303-1306.
70 WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977 Syrnp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
BIOENERGETICS OF BREEDING DABBLING DUCKS
R. B. OWEN, JR., AND K. J. REINECKEI
School of Forest Resources, University of Maine, Orono, Maine 04469
Abstract: A thorough understanding of waterfowl reproduction requires an appreciation for the energy requirements of breeding birds. Recent reviews of avian energetics are used as a starting point for this synthesis of information on the bioenergetics of breeding waterfowl. A major obstacle to our understanding is the inability to measure directly the energy needs of free-living birds. The data available for Anatini in particular, and Anseriformes in general, are incomplete and often inconsistent. Such basic information as basal metabolic rates (BMR) and lower critical temperatures (LCT) has not been satisfactorily established. )I'he present analysis is organized around a FORTRAN model that estimates the daily energy requirement during the breeding season as a summation of increments to BMR, and then calculates and partitions the daily energy intake. Manipulation of program parameters and inputs suggested that egg production and behavior, especially flight, are the most energy demanding activities. Analysis of tempera ture data from Maine indicated that thermoregulation is a minor energy expenditure for the black duck (A nus rubripen) during the breeding season. For female dabbling ducks, the daily energy requirement during egg laying is 3.4 times BMR, whereas the requirement for males peaks at 2 times BMR during prenesting. An analysis of the model indicated that the total daily energy requirement and dry matter intake during the breeding season were most sensitive to estimates of BMR, flight time, energy cost for incubation, and percent fiber in the diet. Values for LCT and for the contribution of specific dynamic effect to the energy cost of thermoregula tion are more important for wintering than breeding Anatini. Additional research on the above relationships would further our understanding of the energy requirements of waterfowl. The model suggests four strategies used by temperate and arctic nesting waterfowl to meet net energy requirements for reproduction: (l) reliance on exogenous energy supplemented by a small but important endogenous energy reserve accumulated away from the breeding area (e.g., black duck), (2) reliance on exogenous energy supplemented by a small but important endoge nous energy reserve accumulated on the breeding area (e.g., wood duck fAix sponsa] ), (3) reliance on a large proportion of endogenous energy reserves accumulated away from the breed ing area (e.g., blue goose [Anser caerulescens D, or (4) reliance on a large proportion of endoge nous energy reserves accumulated on the breeding area (e.g., American eider [Somatena mol lissima] ).
I Present address: Migratory Bird and Habitat Research Laboratory, U.S. Fish and Wildlife Service, Laurel, Maryland 20811.
71 BIOENERGETICS OF BREEDING DABBLING DUCKS
Every organism interacts with a set of and ideas on the energetics of avian environmental factors that may be reproduction, and to A. N. Moen (1973) physical (e.g., temperature, wind), for his analytical approach to energy chemical (e.g., quality of the diet), or relationships. T. J. Shriner, University biological (e.g., courtship and predation). of Maine, volunteered many hours of pro Life history strategies enable birds to gramming expertise. This study was maximize their reproductive effort with supported by funds from U. S. Fish and in this sphere of interaction. Part of the Wildlife Service Contract No. 14-16-0008 strategy is the allocation of available 874 and Hatch Act funds administered resources during the reproductive period. through the University of Maine Agricul Energy is a common denominator for tural Experiment Station; computer time expressing the requirements and activi was provided by the University of Maine ties of a duck during the reproductive Computing Center. season. The consumption of midge larvae (Chironomidae), territorial defense, egg LITERATURE REVIEW production, and temperature regulation can each be expressed in terms of calories Gessaman (1973), King (1973), Ricklefs gained and lost. Energy requirements (1974), and Kendeigh et al. (1977) re during the breeding season can be met by viewed the concepts and methodology of exogenous sources such as midge larvae avian energetics. Ricklefs' data are or from endogenous stores in the form of drawn from a variety of taxa, and his fat and protein. discussions provide only a starting point Krapu (1979) has shown that breeding for anyone working with a particular females have specific nutritional require taxonomic group. Unfortunately, the ments (e.g., increased protein and cal data necessary to understand the energy cium during the egg laying period), and relationships of breeding Anseriformes Swanson et al. (1979) have discussed the are not available, and limiting the dis manner in which birds adjust their cussion to dabbling ducks compounds the feeding habits and choice of foods to problem. Nevertheless, interest in the meet these nutritional needs. At the bioenergetics of dabbling ducks is in same time, however, ducks must also ful creasing and the available data are fill their energy requirements, and it is reviewed below. the integration of these needs that this Laboratory data on the energy cost of symposium is addressing. thermoregulation are available for mal The objectives of this paper are to: (1) lards (Anas platyrhynchos) (Hartung review studies related to the bioenerge 1967, Prange and Schmidt-Neilsen 1970, tics of breeding dabbling ducks, (2) McEwan and Koelink 1973, Smith and discuss current methods and their appro Prince 1973), black ducks (Hartung 1967, priateness for energy studies, (3) provide Berger et al. 1970, Wooley and Owen a detailed energy partition diagram 1977), and blue-winged teals (A. discors) specific for birds, (4) present a model for (Owen 1970). Information on changes in calculating energy costs during the body weight and/or composition has breeding season, (5) compare the energy been obtained for mallards (Folk et al. requirements of breeding ducks under 1966), black ducks (Reinecke 1977), blue alternative sets of model parameters and winged teals (Harris 1970), pintails (A. inputs, (6) identify research needs, and acuta) (Krapu 1974a, Calverley and Boag (7) examine management decisions as 1977), and gad walls (A. strepera) (Oring they relate to energy metabolism. 1969). Time budgets for various activities We owe a debt of gratitude to R. E. during the reproductive period have been Ricklefs (1974) for his synthesis of data calculated for gadwalls (Dwyer 1974,
72 WATERFOWL AND WETLANDS SYMPOSIUM
1975), blue-winged teals (Miller 1976), abolic rates (RMR) (King 1974), lower and black ducks (Wooley and Owen critical temperatures (LCT), and the cost 1978). Incu bation behavior has been of thermoregulation. Gas exchange, described for mallards by Caldwell and adjusted for the respiratory quotient Cornwell (1975) and blue-winged teals by (RQ), is converted to energy expended in Miller (1976). Converting time budgets to calories (Depocas and Hart 1957). energy costs is difficult, and data ob Digestion trials have been used to tained from other taxa are usually measure nutrient retention and to esti applied. For Anseriforms, the cost of mate the cost of thermoregulation, tissue swimming has been measured in mal growth, and egg production. Generally lards (Prange and Schmidt-Neilsen the energy content of the feces is sub 1970), and Wooley and Owen (1978) have tracted from the energy content of the attempted to measure the energy cost of food without a correction for kidney a variety of activities in black ducks. waste. For digestion trials the energy Composition of the diet during the expended is called existence energy breeding season is available for mallards (Kendeigh 1949) and is not directly (Perret 1962), black ducks (Reinecke equivalent to BMR, because the birds are 1977), blue-winged teals (Swanson et al. free to feed and exhibit limited activity. 1974), pintails (Krapu 1974a,b) and gad Both indirect calorimetry and food con walls (Serie and Swanson 1976). Proxi sumption can be used in the laboratory mate nutrient and energy content of to assess the energy cost of a treatment waterfowl foods was documented by such as low temperature. Unfortunately, Bardwell et al. (1962),Driver et al. (1974), in the field aduck's thermal environment Krapu and Swanson (1975), and Reinecke is modified by temperature, wind, and (1977). Digestibility of commercial diets radiation simultaneously so that it is was determined for mallards by Sugden very difficult to measure the microcli (1971) and for several dabbling species mate affecting a bird (Moen 1973, King by Miller (1974). Finally, the nutritional 1974, Mahoney 1976). The problem is requirements for egg production were complex, but probably more significant studied in mallards (Holm and Scott for dabbling ducks in the winter than 1954, Foster 1976) and pintails (Krapu during the breeding period. and Swanson 1975). Two methods have been used to obtain Thus a variety of dabbling ducks has estimates of daily energy expenditures been studied, but the information on (DEE) for birds in the field. Carbon diox particular species is inadequate to ide production, and 02 consumption if describe the energy requirements during the RQ is known. can be estimated from the breeding season. Data from several the turnover rates of D20 and H2180 waterfowl species must be combined within the body (Mullen 1973). Birds are with information from other avian captured and injected with heavy water, groups to estimate an energy budget blood samples are taken, and the birds during the reproductive period. are released. After a specified period the birds are recaptured and blood samples again are withdrawn for analysis. This REVIEW OF METHODS method has been tested on a variety of species with variable success, but to date Indirect calorimetry for measuring no waterfowl have been studied. The oxygen (02) consumption and/or carbon drawbacks of the technique are (1) the dioxide (C0 2) production has been used birds must be recaptured, (2) it is expen in the laboratory to determine basal sive, and (3) one does not obtain data on (BMR), standard (SMR), or resting met the cost of specific activities during the
73 BIOENERGETICS OF BREEDING DABBLING DUCKS
experimental period. and heart rate-metabolism relationships Daily energy expenditures also can be (Wooley and Owen 1977). Thus differ estimated from time activity budgets for ences in objectives and methods have birds at different times of the year if reduced the value of the data for com increments to BMR are assumed for spe parative purposes. cific activities. It is preferable to observe marked individuals for time activity A VIAN ENERGYPARTITION analysis, and in some instances only telemetry is effective, as in determining We found it necessary to modify activity at night. Limited data on the existing energy partitions to obtain a energy expenditure for specific activities satisfactory model for interpreting the by dabbling ducks suggest that the esti waterfowl data. Our partition (Fig. 1) mates currently in use (Dwyer 1975) are was derived from Crampton and Harris reasonably accurate (Wooley and Owen (1969:58-59) with three modifications. 1978). First, the mixture of renal and intestinal Important information concerning the waste products in birds is combined energy balance of breeding waterfowl within the fecal energy component. can be obtained by monitoring changes Second, we have identified endogenous in body weight and carcass composition. energy (tissue and fat catabolism) as an Reductions in lipid or protein reserves alternate source of net energy, and have indicate periods of metabolic stress and indicated a potential pathway for the measure endogenous energy inputs dur waste heat from catabolism to be used ing reproduction. Although few studies for thermoregulation. The final modifi of dabbling ducks have measured varia cation was a separation of the behavioral tions in carcass composition (Reinecke energy requirement from the mainte 1977), work on other waterfowl (Ankney nance and productive components 1974, Korschgen 1977, Drobney 1977) has because of difficulties in assigning speci highlighted the value of this technique. fic activities (e.g., preening, feeding, In summary, several methods have territorial defense) to either a mainte been used under both laboratory and nance or productive function. field conditions to determine components of the energy budget of dabbling ducks. THE MODELLING PROGRAM Much of the work is fragmented and has involved techniques with varying accu General Feature. racy and precision. Rigorous statistical The energy partition from Fig. 1 pro evaluation has not been possible in most vided the conceptual framework for studies. developing a FORTRAN computer model Laboratory experiments should be of anatid energy requirements. At pres more amenable to statistical treatment, ent the modelling program deals only but results from studies of related spe with the breeding pair from the time of cies have been inconsistent. For example, arrival on the nesting area to the aban we used data from a variety of studies donment of the brood by the female or of to estimate LCT and basal metabolic the female by the male. rates. Unfortunately, the data came from The structure of the program is experiments that were designed to mea illustrated in the flow diagram of Fig. 2. sure the influence of other parameters Complete details of the program are such as the effect of oiling (Hartung available on request. The components of 1967, McEwan and Koelink 1973), cost of the energy partition are also the system swimming (Prange and Schmidt-Neilsen state variables of the model. The der iva 1970), cost of flight (Berger et al. 1970), tion of each component is explained in a
74 Tissue Cain
r- Produeli .. --{ Energy ::::J Egg >>-3 Production trl ~ "'Jo (,ogeaous ::::J Net ~Net t'" Energy > Apparent .-- Digestible I ""0' S I""' Maintenance Energy Endogenous ::::J -l True L- Energy ----.- BMR <.T' Net trl Metabolizable - >-3 Energy Energy ---., t'" Cross _ I Energy Metabolic f- True > Fecal ----.j Digestible I Food Residue S L------Thermoregulation UJ L Fecal Energy Energy Unnary I + --r UJ Energy I >< Energy U'nury Energy I is: 1) Food He'd Spedfic I Endogenous '"d 2) Slue- EndogOROUS L-- Dynamic ..J I-- Urinary o Effect Energy UJ Fecal a Food is: i Residue Metabolic L Fecal Energy
Fig. 1. Avian energy partition modified from Crampton and Harris (1969). The broken lines indicate hypothetical pathways of energy flow, Body Basal Metabolic Endogenous Lower RtproductiW! Metabolic Fecal Urinary Critical Uermoregulalion Chronology Weight Rate Energy Energy Temperature ----r-- ob:I t"l Z t"l 1~~7ation ;:0 I CJ t"l I Printer .-,3 (') - U"1 Request, Di~nsion, Read Read, Program Initialize Output Tektronix o Declare Temperature ""j Document Time Values (31) Grapllics Arrays, Data Set Input Structure Day (llegil -1) Variables Display b:I Variables 1911 - 1977 ;:0 -l Parameters t"l a> t"l Calcomp tJ Plotter Z CJ tJ >b:I b:Ie- Z CJ Egg Weight Weight Diet Energy Behnior tJ ProductiOll Gains Losses Partition c::: (') :>:: U"1 Fig. 2. Flow chart for the computer program modelling the bioenergetics of breeding dabbling ducks. WATERFOWL AND WETLANDS SYMPOSIUM
later section. In its current form the tion. The program terminates with the modelling program is strictly determinis ou tpu t of the energy variables to a tic. Program execution requires the input printer, graphics unit, or electromechani of a temperature data set and 10 vari cal plotter. ables specifying the size and timing of The calculations performed by the the reproductive effort; the input vari modelling program fall in three groups, ables are summarized in Table 1. one dealing with energy requirements, Subroutines TIMING and INTLIZ are another with energy sources, and a third called before the main program is with the partition of energy intake. The entered. TIMING uses the input para daily net energy requirement is esti meters to develop a time structure for mated from the maintenance, behav events during the breeding season, ioral, and productive requirements. Once including dates for hatching of the the net energy requirement is known, the clutch, fledging of the juveniles, and contributions from exogenous and molting by the adults. Subroutine endogenous sources can be estimated. INTLIZ provides values for several vari Then, the requirement for exogenous ables for the day prior to arrival on the energy and estimates of digestive effi nesting area because certain components ciency are combined to derive the gross of the energy partition are functionally energy intake that is partitioned as in dependent upon the daily net energy Fig. 1. requirement as well as being terms in the summation used to calculate this Energy Requirements value. The program, therefore, must use The daily net energy requirement, values from the previous day for these expressed as the sum of the maintenance, calculations. behavioral, and productive require The main program is now entered; its ments, was calculated as follows (all primary function is to give access to the units are kcal unless otherwise stated): 13 subroutines that describe secondary NRGREQ (DATE) = MAINRG (DATE) relationships (e.g., body weight) or cal + BEHNRG (DATE) + PRONRG culate components of the energy parti (DATE) Table 1. Input variables required for execution of the modelling program. Parameter Interpretation Value Specie Species 1= Black duck Agesex Age and sex 1=Adult female, 2 =Adult male Arival Date of arrival at nesting area Julian date, i.e., 110 Frsteg Date first egg laid Julian date, i.e., 125 Devper Days required for maturation of a follicle Approximately 7 Clutch Clutch size As desired Incub Incubation period in days 23 for black duck Incost Energy cost of incubation as increment to BMR 0.0 to desired level Sdeper SDE available for thermoregulation 0.0 to 1.0 Unkcst Energy cost of unknown activity as increment to BMR 0.0 to desired level Temp 71-77 Daily maximum and minimum temperatures (C) March to July 1971-77 For Orono, ME
77 BIOENERGETICS OF BREEDING DABBLING DUCKS
The components of maintenance energy critical temperature for body size and are basal metabolic rate, metabolic fecal acclimatization to ambient temperature. energy, endogenous urinary energy, and The effect of seasonal acclimatization thermoregulation: (average temperature previous 14 days) MAINRG (DATE) = BMR (DATE) + on the lower critical temperature is METFEC (DATE) + ENDUNE (DATE) illustrated in Fig. 3. In our model the + HETREG (DATE) adjustment of the lower critical for Basal metabolic rate, taken from Wooley ambient temperature occurs daily, and Owen (1977) and others (Hartung whereas for the birds this adjustment 1967, McEwan and Koelink 1973, Smith may be seasonal in relation to feather and Prince 1973),was expressed as: molts. The effect of body size on lower critical temperature as modelled in the BMR (DATE) = 75 * Met Body Wt (kg) program is shown in Fig. 4. We have where Met Body Wt. (kg) = (Body Wt. assumed that the effects of acclimatiza [kg] )0.72 Metabolic fecal energy was tion and body size are independent and modelled as a function of body weight, additive; the lower critical temperature dietary fiber content, and dry matter is more sensitive to seasonal acclimati intake (after Brody 1945:374-397), and zation than to changes in body size. This was expressed as: treatment of lower critical temperatures METFEC (DATE) =0.08 g N * Met Body may not be biologically realistic due to Wt (kg) * 8.22 kcal/g N Excreted * ([% lack of data, but it does adequately repre Dietary Fiber * 100/23.0 + 0.96) + sent the available data (McEwan and m.M. Intake (DATE-I) (g)/Maintenance Koelink 1973, Smith and Prince 1973, D.M. Intake (DATE-I) (g»)) Wooley and Owen 1977). Both the illus where N =nitogen, D.M.= dry matter, trations and the modelling program and maintenance intake = the ratio of assume that regressions of metabolism maintenance to gross energy intake on ambient temperature extrapolate to a times dry matter intake. Metabolic fecal body temperature of 40 C (see West energy will increase as dry matter intake 1962). increases, and will double with a change Once the lower critical temperature is in dietary fiber from 0 to 24%. established, the number of hours, if any, The endogenous urinary energy below the thermoneutral zone is deter estimate was related to the net energy mined by solving for the intersection of requirement, metabolic body weight, and the lower critical temperature with a BMR (Brody 1945:374-397), and was cal sine curve representing ambient daily culated as: temperature (Fig. 5). Daily temperature ENDUNE (DATE)= 0.2 g N * 8.22 kcal/g was modelled with two sine curves hav N Excreted * Met Body Wt (kg) * ing amplitudes equal to the difference NRGREQ (DATE-l)/BMR (DATE-I) between the maximum or minimum arid Thermoregulation was the most diffi the average temperature, and having a cult component of maintenance energy periodicity of one-half the light or dark to model. Ideally the calculation would period. For the time spent below the include (1) seasonal changes in thermal thermoneutral zone, the effective tem conductance due to molt, (2) variations perature is defined as the mean of the in body size and thus surface to volume lower critical and minimum tempera ratio, and (3) differences in plumage con tures, and the energy requirement is ductance among species. Because these calculated by solving the equation relat data are lacking, we constructed a ing metabolism to temperature (Figs. 3, simplified model that adjusts the lower 4) for metabolic rate at the effective
78 WATERFOWL AND WETLANDS SYMPOSIUM
~l temperature. Finally, the energy incre ment for thermoregulation is obtained by subtracting BMR from the energy requirement for any time below the lower critical: HETREG (DATE) =( l75/(Lower Critical Temp [C ] - 40)1 *Effective Temp Lower Critical TempI + 75) * Met Body Wt (kg) * Hours/24.0 - BMR (DATE) * Hours/24.0 - SDEPER * SDENRG (DATE-I) - 0.2 * ENDNRG (DATE-I) where SDENRG = specific dynamic ef Fig. 3. Effect of temperature of acclimatiza fect, SDEPER= proportion of SDE avail tion (-5, 5, 15 C) on lower critical temperature able for thermoregulation, and END and metabolic rate of a duck weighing 1 kg. NRG= energy contributed by fat and tissue catabolism. The productive energy requirement was calculated as the sum of require ments for tissue growth (ovary, oviduct, testis) and egg production: PRONRG (DATE)=EGCOST (DATE) + TISNRG (DATE) For estimating the energy increment of egg production, we assumed that the cumulative growth of a follicle is sigmoid and that the energy requirement for each follicle over time is a bell-shaped curve. Fig. 4. Effect of body weight (0.25-1.5 kg) on King (1973:88-92) discussed use of the lower critical temperature and metabolic rate for a duck acclimatized to 10C. sine curve as a model for the energy re-
MAXIMUM DAILI TEMP
AVERAGE PHClTClPERIClD SCClTClPER I ClD i DAILI 24 HClURS TEMP
UIWER CR I TICAL TEMP \ EFFECTIVE TEMP \ / MINIMUM DRILl TEMP Fig. 5. Use of sine curves as a model for the derivation of the effective temperature and the number of hours spent by a duck below the LCT given the daily maximum and minimum tem peratures and photoperiod.
79 BIOENERGETICS OF BREEDING DABBLING DUCKS
quirement of egg production. As pointed was calculated as: out by Drobney (1977:82), this model TISNRG (DATE) = 0.25 *Tissue Gain (g) does not account for the time difference *5.65 kcal/g + 1.0 * Fat Gain (g) * 9.45 in yolk and albumen production. The cost kcal/g of egg production is calculated as the where tissue gain is the sum of ovarian, sum of all sine curves representing folli testicular, and oviductal growth. cles developing at a given time. In our The energy increment for activity was simulations, the efficiency of egg produc expressed as a sum of products of the tion (egg energy/metabolizable energy) time spent in each activity multiplied by averaged 73% and was calculated as: the energetic cost of the activity: . n ~ 12 EGCOST (DATE)= sin (i) BEHNRG = (DATE).:2: Activity (i) i=1 1=1 Figures 6 and 7 illustrate the energy requirement for egg production when (Hours)/24.0 * Cost Activity (i) clU'tch size is greater and less than the where the cost of an activity is expressed number of days required for follicular as an increment to BMR, and activities maturation. The energy requirement for 1, ... , 12) =rest, stand, preen, walk, feed, egg production reaches a plateau when alert, swim, bathe, chase, unknown, in clutch size exceeds developmental period, cubate, and fly. and the bird can decrease its peak energy EMrgy Sources requirement for egg production only by The daily net energy requirement is reducing its clutch size to less than the satisfied via exogenous and endogenous developmental period, by producing a sources. In the model both fat and struc smaller egg, or by increasing the laying tural tissue are considered to be sources interval. of endogenous energy. From 50 to 150 g Estimates of tissue energy were based of fat may be catabolized during the pre on descriptions of testicular, ovarian, laying, laying, and incubation periods and oviductal growth by Johnson (1961), (Drobney 1977:59, Reinecke 1977:69). We Phillips and van Tienhoven (1962), Drob have assumed a ratio of 1 g per day fat ney (1977), and Calverly and Boag (1977). input during prenesting, 2 g during egg Nonfat tissue was assumed to have a dry laying, and 1 g during incubation; this matter content of 25%. Tissue energy pattern of weight loss is consistent with
Fig. 6. Percentage of egg energy accumulated in a developing ovary (upper curve) in which the clutch size is greater than the number of 1[l't£. IN DRYS . days required for the growth of a follicle. Fol liculargrowth was modelled with a sine curve Fig. 7. Percentage of egg energy accumulated (after King 1973). The maximumdaily cost of in a developing ovary (upper curve) in which any individual follicle is 28.6% times the the number of days required for the growth of energycontentofthe egg. a follicle is greater than the clutch size.
80 WATERFOWL AND WETLANDS SYMPOSIUM
Harris' (1970) data for blue-winged (g)/ % D.M. teals. Testicular. ovarian. and oviductal The dry matter content of the diet varied regression were also considered to. be with season and with sex of the bird as sources of endogenous energy. For both described in recent literature (Krapu fat and tissue catabolism. an efficiency 1974b, Swanson et al. 1974, Serie and of 80% for conversion to net energy was Swanson 1976). assumed. Endogenous energy was cal Dry matter intake was converted to culated as: gross energy with an expression for ENDNRG (DATE)= 0.25 * Tissue Loss dietary caloric density. as follows: (g) * 5.65 kcallg + 0.8 * Fat Loss (g) * GRONRG (DATE)=DINTAK (DATE) 9.45 kcallg (g) *Caloric Density (kcallg) Exogenous energy, the portion of the net where Caloric Density=(% Protein * 5.65 energy requirement met by dietary in kcallg) + (% Fat * 9.45 kcallg) + (% take, was calculated by difference: NFE * 4.15 kcallg) + (% Fiber * 4.15 EXONRG (DATE)=NRGREQ (DATE) kcallg) ENDNRG (DATE) Specific dynamic effect was estimated from gross energy intake and dietary Energy Partition composition with data from Ricklefs (1974:168): . The exogenous energy estimate was SDENRG (DATE) = GRONRG (DATE) * the basis for calculation of dietary ([% Fat * 0.13J +.[% Protein *0.31J + energy intake and its subsequent parti [% NFE * 0.181) tion. Metabolizable energy was expressed Food residue urinary energy is related as the sum of exogenous and specific to the difference between dietary protein dynamic effect: intake and the current protein require METNRG (DATE)= EXONRG (DATE) ment. For egg-laying females the model + SDENRG (DATE-1) assumes an 18% protein requirement; all The sum of metabolizable and food resi other adults require 12% (Scott 1973, due urinary energy equalled true Foster 1976).The equation is: digestible energy: FRESUE (DATE) = (% Dietary Protein DIGNRG (DATE)=METNRG (DATE) % Protein Required) * DINTAK (DATE) + FRESUE (DATE-1) (g) * (8.22 kcal/g N Excreted/6.25 g N/g Dry matter intake is the digestible Protein) energy requirement divided by the Apparent digestible. urinary. fecal food digestible energy content per gram of dry residue, and fecal energy were all de matter. In the model digestibility has rived from existing variables: been adjusted only for the level of dietary URINRG (DATE)=FRESUE (DATE) crude fiber (see Miller 1974). The equa + ENDUNE (DATE). tion is: APDNRG (DATE) =DIGNRG (DATE) DINTAK (DATE)=DIGNRG (DATE)/ METFEC (DATE)-URINRG (DATE). Digestible energy per g D.M. FECFOD (DATE) = FECNRG (DATE) where Digestible energy per g D.M. METFEC (DATE)-URINRG (DATE). =% Fat * (0.95 - 3.0 * [% FiberJ2) * 9.45 FECNRG(DATE)=GRONRG(DATE) kcallg + % Protein * (0.88 - % Fiber) * APDNRG (DATE) 5.65 kcal/g + % NFE * (0.96 - 6.0 * [% Fiber12)* 4.15 kcallg RESULTS AND DISCUSSION Daily wet matter intake was estimated from dry intake by the equation: We completed two types of analyses WINTAK (DATE)(g)=DINTAK (DATE) with the modelling program. In the first
81 BIOENERGETICS OF BREEDING DABBLING DUCKS
we executed the model with what we taken from Reinecke (1977:63), and for believe are the best estimates for para males from the pattern for mallards meters describing the breeding effort of described by Dement'ev and Gladkov male and female black ducks. We then (1967) (Fig. 8). Endogenous energy inputs manipulated several components of the were discussed above. Dietary composi model to identify those variables to tion varied seasonally, and during egg which the daily energy requirement is laying it was approximately 8% fat, 35% most sensitive. protein, 30% NFE, 14% fiber, and 13% ash; dry matter content was 35% (Swan Energy Requirements, Sources, and son et al. 1974, Reinecke 1977). Tempera Partition ture data from 1975 were used, and SDE was not allowed to substitute for any of Several assumptions of the model not the energy increment due to thermo discussed above are presented here. For regulation. The energetic cost of incuba our best estimate of the energy require tion and unknown activity was subjec ments of breeding black ducks, we as tively set at 1.5* BMR. sumed that (1) the breeding pair arrived Executing the program with these on 20 April, (2) the first egg was laid on assumptions generated the output 5 May, (3) clutch size was 10, (4) incuba illustrated in Figs. 9-18. The peak energy tion required 23 days, (5) the male aban requirement and dry matter intake (Figs. doned the female 10 days into incubation, 9, 10) for females during egg laying were and (6) the female abandoned the young 275 kcal (3.4 * BMR) and 120 g, respec 5 days before they fledged at 56 days of tively. Few experimental data are avail: age. Changes in body weight during nest able for comparison. King (1973:94-96) ing can affect the daily energy require estimated the cost of maintenance plus ment and the availability of endogenous the production of 1 egg per day at 3.5 energy. For our work the annual cycle of times BMR. This did not, however, ac body weight for female black ducks was count for any additional activity asso-
0 MRLE MOLT N
<..:l- ~ ~ I- ..: :I: LAST EGG <..:l fLlGHTLES U.J FEMRLE 3: 0 HATCH 0 > 0 '"CD 0 '"0
APAIL 1ST MAT 1ST JUNE 1ST JULY 1ST AUGUST 1ST ~ 9J+---,--l-----.------,--l-----,------,----l-----,------.-L--.....-----,---L------,150 IS 30 60 75 90 105 120 135 TIME IN DAYS Fig. 8. Annual weight curves for male and female black ducks (after Reinecke 1977, Dement'ev and Gladkov 1967).
82 WATERFOWL AND WETLANDS SYMPOSIUM
ciated with a free existence. In another tive season during the period of chasing paper, King (1974:39-40) reviewed esti and increased flight behavior. Maximum mates of the DEE of free-living birds, dry matter intake (80 g) was only two most of which were breeding. The thirds that of a female laying eggs, in majority of the estimates were between spite of the larger size of the male. 2 and 4 times BMR. Our estimates for In Figs. 11-12 the daily net energy dry matter intake are higher than those requirement is shown as a sum of its reported by Foster (1976:40-44) for mal components, each of which is further lards of comparable size (1,100 g), but his subdivided. The maintenance and behav birds were caged and fed a diet contain ioral energy requirements fluctuate only ing less than 5% crude fiber. . slightly, but productive energy increases The energy requirement for males was from zero during prenesting to a value highest (174 kcal) early in the reproduc- (132 kcal) nearly equal to the sum (143
TOTAL DRILY ENEAGY REQUIREMENT
FEMRLE
"'RLE
Fig. 9. Total daily energy requirement of a Fig. 11. Partition of the total daily energy male and female black duck during the breed requirement of a female black duck during the ing season. Time axis is based on Julian calen breeding season. Time axis is based on Julian dar (See Table 1). calendar (See Table 11.
~ PRODUCTIVE ENERGY
EGG PACIDUCT 1t'lN
I fEHRlE
~ o cr_ P\c~------, u o I "'ALl I \ I I "I \ \ -I 1._-~--l--~-~lI - ..-/:1 T 1\55UE PAt'lOUCTI ON ja~ 9:10 109 12B 1\1) 166 2011 ;>.?3 In 166 res TIME IN DRYS T [ME IN OAT5 Fig. 10. Dry food intake of a male and female Fig. 12. Partition of the productive energy of black duck during the breeding season. Time a female black duck during the breeding sea axis is based on Julian calendar (see Table 1). son. Time axis is based on Julian calendar (see Table 1).
83 BIOENERGETICS OF BREEDING DABBLING DUCKS
kcal) of behavior and maintenance. If the of wind or solar radiation on the energy model is realistic, then follicle and ovi cost of thermoregulation, because rele duct growth causes the peak energy vant microclimatic data were unavail requirement to occur when the first egg able. is laid (Figs. 11, 12). Behavioral require ments (Fig. 13) are greatest during pre nesting when flight activity is high. The energy increment for thermoregulation
(Fig. 14) was minimal when we incor HJTAL ORll T ENEAGT REQUIREMENT porated the 1975 temperature data into the model. We did not consider the effect
EXOGENOUS
ENDOGENOUS
I 8 lin t 8 1 5 TI"'£ IN OATS Fig. 15. Relative contributions of exogenous and endogenous energy to the total daily ENEAGY" F'OA ACTIVITT energy requirement of a female black duck during the breeding season. Time axis is based on Julian calendar (See Table 1).
, 12. I 1 186 115 . lUtE IN DAYS Fig. 13. Energy requirement of a female black duck for activity during the breeding season. Time axis is based on Julian calendar (See Table 1).
GROSS ENEAGY INTRKE
:3 . "AINTENANCE ENERGT ~ D ~ ~ U YJI r------.....:::::::::::::======~ D :;: '" t APPRRENT DIGESTISLE '" FECRl
ENDOGENl:!US URI NARY I'1ET~lIC FECAL, I HEAT REGULATION
I • 1~7 18. liS ,. Ill? t • I "5 ". TII'IE IN OATS ." TUtE IN OATS Fig. 14. Partition of the maintenance energy Fig. 16. Partition of the gross energy intake of requirement of a female black duck during the a female black duck during the breeding sea breeding season. Time axis is based on Julian son. Time axis is based on Julian calendar (see calendar (See Table 1). Table 1).
84 WATERFOWL AND WETLANDS SYMPOSIUM
. ~ ~ . . f\
~ ~ ~ ~ ~ h ~ TAUE DIGESTIBLE ENEAGY ~ r' HETFlBOLI lABLE ENEAGY ~; r!J ~! I~ \..----/ !'1ETAB~l f lABlE 1.--1 ::.::~ :.::; EXOGENOUS L
~ ~ J\ SOE fOOD RESIDUE URrNFlflY --./' 9> 10. 128 166 185 m 9>0 109 rae l~6 ,b, m '"TIHE IN OATS '" 11,1T I HE DRYS laS Fig. 17. Partition of the true digestible energy Fig. 18. Partition of the metabolizable energy intake of a female black duck during the intake of a female black duck during the breeding season. Time axis is based on Julian breeding season. Time axis is based on Julian calendar (See Table 1). calendar (See Table 1).
The relative contributions of endoge Sensitivity Analyses nous and exogenous energy to the net In the model, estimates of the daily net energy requirement are shown in Fig. 15. energy requirement are dependent on the With an input of 2 g fat per day during constant (i.e., 75) used to calculate BMR egg laying, endogenous energy was from metabolic body weight. Although approximately 6% of exogenous. The we have chosen 75 as the best estimate gross energy intake calculated from the for the constant, a wide range of values exogenous energy requirement is parti has been reported (Wooley and Owen tioned in Figs. 16, 17, and 18, which show 1977, Prince, personal communication). the magnitude of the inefficiencies asso By varying the value of the constant in ciated with digestion and intermediary the model (Table 2), we calculated that metabolism. Sugden and Harris (1972), an error of 22% in the estimation of BMR for example, reported that lesser scaups (70 versus 90 * Met Body Wt.) would (Aythya alfinis) metabolized 69% of a cause an 11 to 12% increase in the energy commercial ration. In the model metab requirement and dry matter intake. Esti olizable energy averaged 64% of gross mates of energy requirements based on energy for natural diets higher in crude the summation of increments of BMR fiber than were commercial preparations are therefore sensitive to estimates of
Table 2. Effect of increasing the value of BMR on the daily energy requirement and dry matter intake of female dabbling ducks during laying. BMR Daily energy requirement Dry matter (kcal) Multiple of BMR Kcal intake (g) 70' Met Body Wt 3.5 266 116 75' Met Body Wt 3.4 275 120 80 • Met Body Wt 3.3 283 124 85 • Met Body Wt 3.2 292 128 90 • Met Body Wt 3.1 300 132 100' Met Body Wt 2.9 317 139
85 BIOENERGETICS OF BREEDING DABBLING DUCKS
Table3. Effect of varying the lowercritical temperature on thermoregulation and the daily energy requirement offemale dabbling ducksduring egglaying. Lowercritical Energy requirement during egglaying (kcal) Thermoregulation temperature (C) ThermoregulatIOn Total as % of total Control o 2,227 0.0 Control + 2.0 o 2,227 0.0 Control + 4.0 o ~227 0.0 Control + 6.0 o ~227 0.0 Control + 10.0 33 2,260 1.5 0.0 o 2,227 0.0 5.0 o ~227 0.0 10.0 28 2,254 1.2 15.0 88 2,315 3.8 20.0 237 2,465 9.6 25.0 476 2,706 17.6 the metabolic constant. the potential for heat energy from SDE None of the temperature data sets for to offset the cost of exposure to tempera spring 1971-77 produced significant tures below LCT (Crampton and Harris energy requirements for thermoregula 1969). To illustrate this relationship, we tion. We used the model to simulate a varied the availability of SDE from 0 to wide range of values for LCT. Relatively 80% with LCT at 25 C to generate a signi large changes in LCT had little effect on ficant requirement for heat regulation the daily energy requirement (Table 3). (Table 4). Even at this elevated LCT the Incrementing the standard estimate in cost of thermoregulation was eliminated the model by 10 C caused a 33 - kcal re with inputs of SDE at 40 to 60%. quirement for thermoregulation during Kendeigh et al. (1977:146-147) suggested the entire laying period. Only at unrealis that 100% of SDE may be available for tic LCT values of 20 to 25 C did the re thermoregulation. The availability of quirement for thermoregulation become SDE may be of little importance to significant. Despite the insensitivity of breeding birds but could be highly signi the model to changes in LCT during the ficant during winter. breeding season, better estimates of LCT The response of the energy require are critical for understanding the ener ment to variations in the cost and dura getics of wintering waterfowl. tion of incubation, unknown, and flight Another aspect of thermoregulation is activity was simulated with the model.
Table 4. Effect of increasing the availability of SDE for thermoregulation on daily energy requirements of female dabbling ducks during the entire egg laying period. Lower critical temperature is held at 25 C. Availability Energy requirement Thermoregulation ofSDE (%) Thermoregulation Total Multiple as % of total (kcal) (kcal) ofBMR o 476 2,706 4.0 17.6 20 291 2,515 3.7 11.6 40 132 2,355 3.5 5.6 60 11 2,235 3.4 0.4 80 o 2,224 3.4 0.0
86 WATERFOWL AND WETLANDS SYMPOSIUM
Table 5. Effect of increasing the energetic cost of flight activity on the daily energy require ment and dry matter intake of female dabbling ducks during prelaying.
Cost of Daily energy requirement Dry matter flying (kcal ) Multiple of BMR Kcal intake (gl 8.0' BMR 1.8 146 66 12.5' BMR 1.9 150 68 15.0' BMR 1.9 155 7fl
Given the amount (15) min) of flight acti The existence of an energy require vity per day programmed for the pre ment for incubation that exceeds normal laying period, the energy requirement is heat loss is a controversial topic (King not very responsive to large changes in 1973, Ricklefs 1974). The data in Table 8 the energetic cost of flight (Table 5). show the effect of varying the cost of However, as flight time was increased incubation from 1.2 to 2.1 BMR. We ob from 0.5 to 1.5 h, the energy requirement tained the latter value by assuming that rose 10 to 20% (Table 6). In the future, the clutch of eggs requires as much heat modelling may provide a means of relat as a bird of similar weight, but with a ing disturbance, flight activity, energy somewhat lower body temperature.
Table 6. Effect of increased flight and decreased feeding time on the daily energy require ment of female dabbling ducks during egg laying. Flight Daily energy requirement t irne th) Multiple of BMR Kcal Control ;1.4 27;) Control + 0.5 ;16 29;3 Control + 1.0 ;3.8 ;111 Control + 1.5 4.0 3;10 requirements, feeding time, and rates of Energy requirements and dry matter energy intake. intake increased sharply (43%) across Changing the energetic cost of nightly this range of values. Field data on the unknown activity from 1.3 BMR (resting) we ight losses (Harris 1970) and re to 1.7 BMR (feeding) resulted in a 3% stricted foraging time available to increase in dry matter intake (Table 7). incubating females (Miller 1976,Caldwell The analyses suggest that values for and Cornwell 1975) are more consistent unknown activity currently used for with the lower estimates. Korschgen extrapolating from time activity studies (personnel communication) believes that to energy budgets are valid. incubating female eiders function at a
Table 7. Effect of increasing the energetic cost of unknown activity on the daily energy requirement and dry matter intake of female dabbling ducks during egg laying.
Cost of Daily energy requirement unknown activity Dry matter (kcal l Multiple of BMR Kcal intake (g) 1.3' BMR 3.;3 270 118 1.5' BMR :1.4 27.5 120 1.7' BMR :3.4 280 122
87 BIOENERGETICS OF BREEDING DABBLING DUCKS
Table 8. Effect of increasing energetic cost of incubation on the daily energy requirement and dry matter intake of female dabbling ducks.
Cost of Daily energy requirenll'nt Dry matter incubation Multiple of BMR Kcal intake (g) 1.2*BMR 1.:3 103 44 1.5*BMR 1.6 125 55 1.8*BMR 1.9 147 66 2.1*BMR 2.2 173 77 level just above BMR. A reduction in posed that loss of endogenous energy BMR is known to occur in fasting geese stores may reduce the clutch size of dis (Benedict and Lee 1937); the relationship placed prairie pintails attempting to of fasting to metabolic rates in incubat breed in the arctic. ing waterfowl should be investigated in The influence of dietary fiber on the field. energy intake is shown in Table 10. The The potential contribution of endoge model predicted a 29% increase in dry nous energy to the daily energy require matter and energy intake in response to ment is illustrated in Table 9. Given the a 10% change in crude fiber. Female assumptions of the model, endogenous dabbling ducks that use invertebrate
Table 9. Effect of increasing endogenous energy on exogenous energy requirement and dry matter intake during egg laying of female dabbling ducks. Control endogenous input was 50 g fat.
Endogenous Daily energy Exogenous Dr,' matter energy (kcal ) requirement (kcal I cneruv (kcal I intake(gl Control 275 267 120 Control * 2 275 259 116 Control *;3 274 252 11:3 Control * 4 274 244 109 Control * 5 274 2:36 106
energy provides 3% of the requirement foods during the laying period not only during laying. At a level 4 times higher, obtain elevated protein levels, but also endogenous sources account for 11% of greatly reduce their dry matter intake. the daily requirement during egg produc tion. Carcass analysis of female wood Energy Metabolism and Reproductive ducks (Drobney 1977) has shown that the Strategy input of this amount of fat (8 g/day) is On the basis of recent field studies and realistic. Calverley and Boag (1977) pro- our simulation analyses, we propose that
Table 10. Effect of varying crude fiber and NFE levels on gross energy and dry matter intake by female dabbling ducks during egg laying.
'7, r!r Energv requirement Gross energy Dry matter Crude fiber NFE as multiple of BMR intake (hal) intake (gl 9 :37 :3.4 468 10:3 11 :3.5 3.4 495 109 12 :J4 3.4 510 112 13 :3:3 3.4 527 116 14 :J2 :3.4 545 120 19 27 :3.4 658 145
88 WATERFOWL AND WETLANDS SYMPOSIUM
temperate and arctic nesting waterfowl tirely upon endogenous fat and protein have evolved four identifiable strategies reserves once laying has begun. Energy for using endogenous and exogenous stores are obtained by the eiders during sources to meet net energy requirements a period of hyperphagia in the vicinity during reproduction. These strategies of the nesting areas. The arctic nesting are (1) reliance on exogenous energy sup blue geese studied by Ankney (1974) plemented by a small but important illustrate an alternative endogenous endogenous energy reserve accumulated energy strategy. Female blue geese feed away from the breeding area, (2) reliance little before the incubation period and on exogenous energy supplemented by a depend like the eider upon nutrient re small but important endogenous energy serves. Unlike the eiders, however, blue reserve accumulated on the breeding geese deposit reserves prior to reaching area, (3) reliance primarily on endoge the nesting area. . nous energy reserves accumulated away Among the selective pressures favor from the breeding area, and (4) reliance ing endogenous energy strategies in the primarily on endogenous energy reserves eider and blue goose are the short, harsh accumulated on the breeding area. We do breeding season of the goose and the nest not intend that all species be placed in predation (Bourget 1973) faced by the one of the categories, but rather suggest eider. For dabbling species, the deposi that certain points within a continuum tion of lipids prior to egg laying will not can be illustrated. affect the net energy requirement during The simulation analyses indicate that egg production, but may be critical in dabbling ducks obtain most of their daily reducing the exogenous energy require requirement as exogenous energy, ment to a level within the foraging whereas endogenous inputs provide a capabilities of the birds. lesser but highly significant energy Because of data limitations the model source that may vary from 6 to 28% of has not been used to investigate factors exogenous energy. The data for female affecting clutch or egg size. In the future, pintails (Krapu 1974a) and black ducks we believe that modelling efforts that (Reinecke 1977) indicate that peak lipid incorporate data on body weights, energy levels occur at the time of arrival in early content of eggs, and nest predation rates nesting species. These females probably for additional species may offer insight store nutrient reserves while occupying into factors affecting clutch size. migrational or wintering habitats. A second strategy for birds using RESEARCHNEEDS primarily exogenous energy is the attain We have shown that the value of ment of reserves after arrival at the several parameters in the model can breeding area. Weight and condition significantly affect the energy require index data (Harris 1970) for blue-winged ments of breeding ducks. Research needs teals indicate that late nesting may be listed below outline studies that could related to this strategy. Drobney's work obtain some of the needed data: (1977) with wood ducks illustrates weight 1. BMR as a function of metabolic and lipid increases in females that ac body weight. Current estimates range cumulate nutrient reserves after arrival from 70 to as high as 100. Indirect calori on the breeding ground. metry can provide more precise esti Korschgen's (1977) research on the mates and also measure seasonal breeding biology of American eiders variation. nesting on the Maine coast showed that 2. Energy requirements for incubation. the females are dependent almost en An opportunity exists with ducks nesting
89 BIOENERGETICS OF BREEDING DABBLING DUCKS
in cavities or other structures to monitor moregulation is unknown. Theoretically 02 consumption by indirect calorimetry. SDE could reduce these energy costs Also, late in the incubation period the significantly during critical winter heavy water technique could be used. It months. would be especially interesting to know 3. Carcass condition. Limited data if BMR drops during the incubation period as Benedict and Lee (1937) have (Reinecke 1977) suggest that the body weights and energy reserves of young suggested for fasting geese. birds are lower than those of adults in 3. Time activity analyses. There is a severe winter weather. This could in need to measure the activity patterns of fluence survivorship rates and physiolo females during the reproductive season. gical condition the following spring. Emphasis should be placed on time in flight, because this is the most energy demanding activity. If possible, the im pact of increased disturbance to the nest MANAGEMENT ing pair should be evaluated. Also, com CONSIDERATIONS bining estimates of feeding time and dry The amount of time spent in flight can matter intake values provided here could increase a duck's DEE significantly. In allow calculation of estimated rates of addition as flight time increases, time resource exploitation. availabl~ for feeding decreases, reducing 4. Food digestibility. Detailed studies the bird's energy intake. Spring trapping, on food habits should provide an esti fishing, and the rapid growth o.f canoeing mate of the proximate analysis of the in the Northeast can cause disturbance composite diet to facilitate application to pairs. Isolation is important during in modelling efforts. Artificial diets this period, and thought should be gi~en could then be prepared having the same to restricting access to major breeding nutrient and energy content so that the areas until incubation is under way. effect of changes in levels of fiber and Unless our estimates of BMR and LCT protein, e.g., could be assessed. are unrealistic, temperature in the 5. Carcass condition. Additional work spring causes little need for thermoregu needs to be done on measuring the levels lation. Instead, temperature affects the of carcass fat and protein in reproducing phenology of nesting indirectly by regu ducks. Nutrient reserves may influence lating ice cover, food availability, and the reproductive strategies, including time opportunity for pairs to disperse. of laying, clutch size, and ability to re The model has provided good estimates nest. of total daily food requirements and The model is sensitive to parameters should help us to place other aspects of that may be especially important during territory such as the requirements for winter: spacing and isolation in better per 1. LCT. Although energy costs for spective. . thermoregulation are small during the Severe winter conditions can affect reproductive period, they may be very the physiological condition of the ducks important in winter. The estimate of the and may influence endogenous energy LCT determines the amount of this cost. stores necessary for early reproduction Few data are available on the relation and large clutch size. In Maine, critical ship of LCT to body size or seasonal black duck winter feeding areas are kept acclimatization. open by tidal amplitude and current 2. SDE. The degree to which SDE can (Hartman 1963). These sites should be meet the energy requirements of ther identified and protected.
90 WATERFOWL AND WETLANDS SYMPOSIUM
LITERATURE CITED
ANKNEY. C. D. 1974. The importance of lem. 683pp. (Transl. from Russian) nutrient reserves to breeding blue geese, DRIVER, E. A.• 1. G. SUGDEN, AND R. J. Anser caerulescens. Ph.D. Thesis. Univ. KOVACH. 1974. Calorific. chemical and of Western Ontario. London. 212pp. physical values of potential duck foods. BARDWELL. J. 1.. 1. 1. GLASGOW. AND Freshwater BioI. 4(3):281-292. E. A. EPPS. JR. 1962. Nutritional analy DROBNEY, R. D. 1977. The feeding ecology, ses of foods eaten by pintail and teal in nutrition, and reproductive bioenergetics south Louisiana. Proc. Southeastern of wood ducks. Ph.D. Thesis. Univ. of Assoc. Game and Fish Commissioners Missouri, Colum bia. 170pp. 16:209-217. DWYER, T. J. 1974. Social behavior of breed BENEDICT, F. G., AND R. C. LEE. 1937. ing gad walls in North Dakota. Auk 91(2): Lipogenesis in the animal body, with spe 375-386. cial reference to the physiology of the goose. Carnegie Institution. Washington. __ . 1975. Time budget of breeding gad D.C. 232pp. walls. Wilson Bull. 87(3):335-342. BERGER, M., J. S. HART. AND O. Z. ROY. FOLK, C., K. HUDEC, AND J. TOUFAR. 1970. Respiration. oxygen consumption 1966. The weight of the mallard, Ana.~ and heart rate in some birds during rest platyrhynchos. and its changes in the and flight. Z. Vergl. Physiol, 66(2):201 course of the year. Zool. Listy 15(3):249 214. 260. BOURGET. A. A. 1973. Relation of eiders FOSTER, J. A. 1976. Nutritional requirements and gulls nesting in mixed colonies in of captive breeding mallards. Ph.D. Penobscot Bay. Maine. Auk 90(4):809 Thesis. Univ. of Guelph, Guelph. Ontario. 820. 93pp. BRODY. S. 1945. Bioenergetics and growth. GESSAMAN, J. A.. ED. 1973. Ecological Reinhold Publishing Corporation, New energetics of homeotherms: a view com York. 1023pp. patible with ecological modeling. Utah State University Press, Logan. 155pp. CALDWELL, P. J .. AND G. W. CORNWELL. 1975. Incubation behavior and tempera HARRIS, H. J .• JR. 1970. Evidence of stress tures of the mallard duck. Auk 92(4):706 response in breeding blue-winged teal. 731. J. Wildl. Manage. 34(4):747-755. CALVERLEY. B. K., AND D. A. BOAG. 1977. HARTUNG. R. 1967. Energy metabolism in oil-covered ducks. J. Wildl. Manage. 31(4): Reproductive potential in parkland and arctic-nesting populations of mallards 798-804. and pintails (Anatidae), Can. J. ZooI. HARTMAN, F. E. 1963. Estuarine wintering 55(8):1242-1251. habitat for black ducks. J. Wild!. Manage. CRAMPTON. E. W.. AND L. E. HARRIS. 27(3):339-347. 1969. Applied animal nutrition. 2nd ed. HOLM, E. R.. AND M. 1. SCOTT. 1954. W. H. Freeman -and Co.• San Francisco. Studies on the nutrition of wild water 753pp. fowl. New York Fish Game J. 1(2):171 DEPOCAS, F.• AND J. S. HART. 1957. Use 187. of the Pauling oxygen analyzer for mea JOHNSON. O. W. 1961. Reproductive cycle of surement of oxygen consumption of the mallard duck. Condor 63(5):351-364. animals in open-circuit systems and in a KENDEIGH, S. C. 1949. Effect of tempera short-lag, closed-circuit apparatus. J. ture and season on the energy resources Appl, Physiol, 10(3):388-392. of the English sparrow. Auk 66(2):113 DEMENT'EV. G. P.• AND N. A. GLADKOV. 127. EDS. 1967. Birds of the Soviet Union. Vol. __ , V. R. DOL'NIK. AND V. M. GAVRI 4. Israel Program for Sci. Trans!., Jerusa LOV. 1977. Avian energetics. Pages 127
91 BIOENERGETICS OF BREEDING DABBLING DUCKS
204 in J. Pinowski and S. C. Kendeigh, MULLEN, R. K. 1973. The D2 0 method of eds. Granivorous birds in ecosystems. measuring the energy metabolism of free Int. Bio. Programme. Vo\. 1~. Cambridge living animals. Pages 32-43 in J. A. Gessa University Press, Cambridge. man, ed. Ecological energetics of home KING, J. R. 1973. Energetics of reproduction otherms. Utah State Univ. Monogr. Ser. in birds. Pages 78-107 in D. S. Farner, ed. Vo\. 20. Breeding biology of birds. National Acad ORING, L. W. 1969. Summer biology of the emy of Science, Washington, D.C. gadwall at Delta, Manitoba. Wilson Bul\. --_ . 1974. Seasonal allocation of time and 81(4):44-54. . energy resources in birds. Pages 4-70 in OWEN, R. B., JR. 1970. The bioenergetics of R. A. Paynter, Jr., ed. Avian energetics. captive blue-winged teal under controlled Nuttall Ornitho\. Club Pub\. 15. and outdoor conditions. Condor 72(2):153 KORSCHGEN, C. E. 1977. Breeding stress of 163. female eiders in Maine. J. Wild\. Manage. PERRETT, N. G. 1962. The spring and sum 41(3):360-373. mer foods of the common mallard (Anas KRAHl, G. L. 1974a. Feeding ecology of pin platyrhynchos platyrhynchos L.) in south tail hens during reproduction. Auk 91(2): central Manitoba. M. S. Thesis. Univ. of 278-290. British Columbia, Vancouver. 82pp. ___ . 1974b. Foods of breeding pintails in PHILLIPS, R. E., AND A. VAN TIENHOVEN. North Dakota. J. Wild\. Manage. 38(3): 1962. Some physiological correlates of 408-417. pintail reproductive behavior. Condor 64(4):291-299. __ . 1979. Nutrient factors affecting repro ductive potential in dabbling ducks. Pages PRANGE, H. D., AND K. SCHMIDT-NIEL in T. A. Bookhout, ed. Waterfowl SEN. 1970. The metabolic cost of swim and wetlands: an integrated review. Proc. ming in ducks. J. Exp. Bio\. 53(3):763-777. 1977 Symp., Madison, WI, N. Cent. Sect., REINECKE, K. J. 1977. The importance of The Wildlife Society. aquatic invertebrates and female energy __ , AND G. A. SWANSON. 1975. Some reserves for black ducks breeding in nutritional aspects of reproduction in Maine. Ph.D. Thesis. Univ. of Maine, prairie nesting pintails. J. Wild\. Manage. Orono. 113pp. 39(1):156-162. RICKLEFS, R. E. 1974. Energetics of repro MAHONEY, S. A. 1976. Thermal and ecologi duction in birds. Pages 152-292 in R. A. cal energetics of the white-crowned spar Paynter, Jr., ed. Avian energetics. Nuttall row (Zonotrichia leucophrys) using the Ornitho\. Club Pub\. 15. equivalent black body temperature. Ph.D. Thesis. Washington State Univ., Pull SCOTT, M. L. 1973. Nutrition in reproduction man. 323pp. - direct effects and predictive functions. Pages 46-68 in D. S. Farner, ed. Breeding McEW AN, E. H., AND A. F. C. KOELINK. biology of birds. National Academy of 1973. The heat production of oiled mal Science, Washington, D. C. lards and scaup. Can. J. Zoo\. 51(1):27-31. SERlE, J. R., AND G. A. SWANSON. 1976. MILLER, K. J. 1976. Activity patterns, vocali Feeding ecology of breeding gad walls on zations, and site selection in nesting blue saline wetlands. J. Wild\. Manage. 40(1): winged tea\. Wildfowl 27:33-43. 69-81. MILLER, M. R. 1974. Digestive capabilities, SMITH, L. G., AND H. H. PRINCE. 1973. The gut morphology, and cecal fermentation fasting metabolism of subadult mallards in wild waterfowl (Genus Anas) fed vari acclimatized to low ambient tempera ous diets. M. S. Thesis. Univ. of Califor tures. Condor 75(3):330-335. nia, Davis. 87pp. SUGDEN, L. G. 1971. Metabolizable energy MOEN, A. N. 1973. Wildlife ecology. W. H. of small grains for mallards. J. Wildt. Freeman and Co., San Francisco. 458pp. Manage. 35(4):781-785.
92 WATERFOWL AND WETLANDS SYMPOSIUM
__ , AND L. E. HARRIS. 1972. Energy of wild birds to environmental tempera requirements and growth of captive les ture. Pages 291-321 in J. P. Hannon and ser scaup. Poult. Sci. 51(2):625-633. E. Viereck, eds. Comparative physiology SWANSON, G. A., M. I. MEYER, AND J. R. of temperature regulation. Part 3. Arctic SERlE. 1974. Feeding ecology of breeding Aeromedical Laboratory, Ft. Wain blue-winged teals. J. Wild\. Manage. wright, AK. 38(3):396-407. WOOLEY, J. B., JR., AND R. B. OWEN, JR. __ , G. L. KRAPU, AND J. R. SERlE. 1977. Metabolic rates and heart rate 1979. Foods of laying female dabbling metabolism relationships in the black ducks on the breeding grounds. Pages duck (Anus rubripesi. Compo Biochem. in T. A. Bookhout, ed. Waterfowl and Physio\. 57(3A):363-367. wetlands: an integrated review. Proc. __ , AND . 1978. Energy costs of 1977 Syrnp., Madison, WI, N. Cent. Sect., activity and daily energy expenditure in The Wildlife Society. the black duck. J. Wild\. Manage. 42(4): WEST, G. C. 1962. Responses and adaptations 739-745.
93
WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Symp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979
INDIVIDUAL VARIATION AND THE ANALYSIS OF MALLARD POPULATIONS
BRUCED.J. BATT
Delta Waterfowl Research Station, R. R. No.1, Portage la Prairie, Manitoba, Canada RIN3AI
Abstract: Scientists interested in social behavior have long recognized the importance of in depth analysis of individual animals as a technique for exposing underlying population mecha nisms. This paper presents evidence that illustrates the importance of applying the same study procedure to gain an understanding of mechanisms that affect population parameters of water fowl, and that are of interest to waterfowl managers. I studied captive mallards (Anas platy rhynchos) and found that laying dates, clutch size, and egg size showed considerable variation among individuals but showed marked consistency within individuals. These results help explain many of the problems inherent in breeding population inventory. The three variables were not significantly different between yearlings and older birds. I hypothesize that, in many species, the measured effects of age on productivity are a consequence of inexperience rather than the breeding strategy. Clutch size, laying date, and renesting potential are not independent variables, although they are often treated as such. Ecologists have devoted considerable represent different segments or cohorts attention to devising methods of trap of populations. This method has been ping and identifying individual animals used in waterfowl research to study the under study. In most analyses, data on effects of age on reproductive potential individuals have been used as single mea (e.g., Trauger 1971, Cooper 1978),renest surements in a sample, the characteris ing potential (e.g., Humburg et al, 1978), tics of which lead to inferences on the population turnover (e.g., Humburg et al. nature of the population. The goal is to 1978),the effect of restocking with hand obtain enough measurements to calcu reared waterfowl (e.g., Sellers 1973, Lee late statistical variance terms. This and Kruse 1973), migrational homing allows a statement about the confidence (e.g, Poston 1974), habitat use and home that the investigator places on his deduc range analysis (e.g., Gilmer et aI, 1975), tions about the population. and continental and regional character More sophistication is achieved when istics of migration and mortality (e.g., data are obtained on individuals that Anderson and Burnham 1976).
95 INDIVIDUAL VARIATION IN MALLARDS
Recently, with the expansion of re Batt and Prince (1978, 1979). Basically, I search dealing with adaptive strategies, collected initiation date, clutch size, and intensive, long-term observations of egg weight data for approximately 80 individuals have provided clues to why individual pairs of penned mallards. animals respond as they do in various These were held under standard pro social and environmental contexts. cedures (Ward and Batt 1972) at the Modern evolutionary theory considers Delta Waterfowl Research Station that natural selection occurs at the level during 1973, 1974, and 1975. The same of individuals with subsequent effects on pairs were held together for the 3 years the population gene pool (Williams 1966). of the study. This allowed an examina Significant advances are being made tion of the consistency of breeding dates with waterfowl in the area of ecoethology and clutch sizes of individual pairs. which attempts to integrate ecology, In 1973, 22 pairs of yearlings were evolution, behavior, morphology, and compared to 20 pairs of adult breeders physiology (McKinney 1973). Future (older than 1 year). Six reproductive management should benefit greatly from parameters were compared between the the products of this approach to water adult and the first year breeders. These fowl research. were: day first egg laid, day last egg laid, Individual variation is often seen as a size of first clutch, number of eggs per nuisance, particularly when it is great. hen, total number of nesting attempts Knowledge of the distribution of varia per hen, and mean egg weight. Unless tion in certain reproductive characteris otherwise stated, comparisons between tics of mallard populations may con groups are by one-way analyses of tribute to more realistic design and variance (Sokal and Rohlf 1969). interpretation of surveys. This study, conducted under the controlled condi RESULTS tions of captivity, also allows interpreta Detailed results were presented in Batt tion of the effects of age on waterfowl and Prince (1978, 1979). No statistically reproduction. Some of these results have significant differences were detected been presented in two other papers (Batt among the six parameters compared and Prince 1978, 1979). The purpose here between the two age groups in 1973. The is to expand the discussion on certain non-significant age effects allowed pool points and to identify some possibly ing of all data for further analyses. important considerations for manage First nest initiation dates varied ment. markedly between individual pairs dur The research was funded by the Ducks ing the 3 years of the study. There were Unlimited Foundation and the North 58, 50, and 43 days between nest initia American Wildlife Foundation through tion by the earliest and latest pairs in the Delta Waterfowl Research Station, 1973, 1974, and 1975, respectively. There and by the Michigan State Agricultural was a significant (P<0.05) difference Experiment Station. H. Prince, D. among individual female laying dates for Beaver, and W. Conley aided with earlier the 3 years but each hen tended to lay interpretations of the data. C. Savage near the same date each year. The re and D. Jelinski provided valuable techni peatability (Becker 1975:23) of laying cal assistance. date was calculated to be 0.57 - 0.07 (SE; N of hens =.0 60). Thus there was marked variation within the sample but consider METHODS able consistency by individual females. The methods used in this study were Clutch size declined significantly described in detail in Batt (1976) and in (P 96 WATERFOWL AND WETLANDS SYMPOSIUM The clutch size and laying date data II were submitted to regression analysis for each of the first three nests for each year 10 of the study. Significant regressions w N were calculated for the first nest for each Vi year, for the 1974 second nests, and for 9 the 1973 third nests (Table 1). Second I U f nests in 1973 and 1975 and third nests in :0 -.J 8 1974 and 1975 did not yield significant u regression equations. The trend in these data illustrates a decline in number of 7 eggs within and between each successive nest in relation to the time of year that initiation occurred. Z All nests for all 3 years' data were 2 3 4 combined and submitted to a further NEST NUMBER regression analysis. The best fit of the Fig. 1. Clutch size decline between first nests data was a curvilinear relationship and renests by a captive flock of breeding mal between initiation date and clutch size lards. Plotted are means, standard errors, and (Fig. 3, Batt and Prince 1979). ranges. tempts. Clutch size was lOA :: 0.2 (X t DISCUSSION SE; N = 151),9.5 ± 0.2 (116),804 t 0.3 (59), and 8.2 ± 0.8 (13) from the first through I assumed that all the necessary re the fourth nest, respectively (Fig. 1). sources for breeding were provided for Analysis of first clutch size and of mean the birds in this study, i.e., a mate, space, egg weight showed significant (P Table 1. Regression equations for clutch size (Y) and time (X)a for the first three nests by individual female mallards in 1973,1974, and 1975. Nest Significance sequence Year Equation n r 2 ofr First 1973 y= 22.76 - 0.10Xb 45 0.39 0.001 1974 y= 21.76 - 0.09X 52 0.21 0.001 1975 y= 20.89 - 0.08X 49 0.12 0.001 Second 1973 y= 15.93 - 0.04X 32 0.08 ns C 1974 y= 24.94 - 0.10X 54 0.20 0.01 1975 y= 9.29 +O.OOX 37 0.00 ns Third 1973 y= 20.79 - 0.07X 13 0.36 0.001 1974 Y==17.76 -0.06X 31 0.04 ns 1975 Y= 4.89 +0.02X 20 0.05 ns a Time is in days. • b The large-Y-intercept values result from using Julian calendar days. C Not significant. 97 INDIVIDUAL VARIATION IN MALLARDS results probably closely reflected the per se. This inexperience seems inevit birds' maximum reproductive capabili able since: 1) most yearlings are less than ties in the captive environment. 10 months old and have never been in a Several inferences about the charac breeding marsh in spring, and 2) they teristics of wild populations can be made must compete with older, more experi from the data. The lack of significant enced birds. age-related effects is inconsistent with Young produced in late mallard nests field data recorded for most species of may have several other disadvantages: ducks. Young birds nest later than adults they may be produced past the peak in the ringed-necked duck (Aythya col quality of their brood-rearing habitat laris) (Mendall 1958), gadwall (Anas and, as a result, have lower fledging suc strepera) (Gates 1962), wood duck (Aix cess; they have been fledged for a short sponsa) (Bellrose et al. 1964, Grice and period of time in early fall and might be Rogers 1965), blue-winged teal (Anas dis less well-equipped to sustain fall migra COTS) (Dane 1966), black duck (A. rub tion; and survivors to the subsequent ripes) (Coulter and Miller 1968), mallard breeding season will be the youngest (Coulter and Miller 1968), and hooded birds in the population and thereby all merganser (Mergus cucullatus) (Morse age-related effects will be compounded et al. 1969). Smaller clutches by yearling in them. breeders have been recorded in the black Under ideal conditions, such as those duck (Stotts and Davis 1960), blue approached in the captive environment winged teal (Dane 1966), ring-necked of this study, yearlings were as produc duck (Coulter and Miller 1968), and tive as were older birds. Data from other hooded merganser (Morse et al. 1969). species suggest that this does not happen Further, a lower degree of rene sting has in the wild. The most exciting challenge been recorded for the yearling gadwall for research is not only to demonstrate (Gates 1962), wood duck (Grice and age-related effects in the wild, but to Rogers 1965), and black duck and mal identify how birds of different ages react lard (Coulter and Miller 1968). Age under various habitat conditions and related effects in the field have been little various population densities. Location studied in the mallard. However, Dzubin on the breeding range should also be con (1969a:152) speculated that young birds sidered (Calverly and Boag 1977, Batt may, in general, be less successful than and Prince 1978). older birds. Bellrose (1976:236) accepted Many studies have shown that renest this idea and stated that mallards breed clutches have fewer eggs than first nests, late or not at all in their first year. He and Johnsgard (1973) provided a number believed that during drought years a of explanations for this phenomenon. large proportion of non-breeders are However, the relationship that I found of yearlings. These assumptions are not yet declining clutch size with time, regard substantiated for mallards with data less of clutch number, suggests that in from the field. the mallard, time alone may be the main Delayed breeding and smaller clutches factor that correlates with clutch size. by yearling waterfowl are often assumed This relationship must be tested in the to reflect a reproductive strategy in wild where other factors also operate. which some ultimate benefit is gained by Population modelers should be interested those genotypes that follow the typical in this result, because the simple func pattern. 1suggest that, in most cases, the tional relationship with time is easily lower reproductive potential shown by incorporated into simulation models. first-time breeders is a consequence of Mean clutch size has a direct effect on inexperience rather than a strategy recruitment rates, which are determi 98 WATERFOWL AND WETLANDS SYMPOSIUM nants of population management strate animal population that has been thor gies. oughly studied (Mayr 1963:129). The The clutch size-time relationship also main cause is that natural environments has implications for the analysis of age are variable in time and space and the related reproductive potential. If young fitness values of gene complexes are birds are forced to nest later because of therefore themselves variable. Ankney inexperience with the breeding environ and Bisset (1976) provided a similar ment, then we would predict a lower hypothesis on how a wide range of egg clutch size. Nesting later also allows less weight genotypes survives in the lesser time for renesting. Thus, we would ex snow goose (Chen caerulescens) due to pect renesting to occur less in yearling annual variations in the optim um date birds. There is a tendency to consider for young goslings to hatch. clutch size, initiation date, and renesting Weather (e.g., Lynch 1964), amongst potential as three independent para many other environmental characteris meters for comparison between year tics, varies widely throughout the mal lings and older birds. But my results lard nesting range and presumably main illustrate that they are probably not. tains much variation in the gene pool for Again, reproductive output appears to be timing of nest initiation. Historically, most related to seasonal chronology. optimum nest initiation date probably Dzubin (1969b) showed the difficulty fluctuated each year relative to earliness of ascribing a given pair of ducks to a or lateness of the transition from winter particular reproductive status. Problems to spring. At the present time, on the arise because in the same breeding prairies of Western Canada, biologists marsh there may be: 1) breeding resident generally accept the idea that virtually pairs, 2) pre breeding residents, 3) pre all early mallard nests are lost to agri breeding transients, 4) renesting resi culture. A large portion of the annual dents, 5) pairs displaced by spacing, or production thus comes from late first 6) nonbreeders. Smith and Hawkins nests or from renests, both of which have (1948) speculated that complete turnover a lower recruitment potential. Modern of the breeding population of a pond cereal crop farming practices limit suit would occur 3 times in a given 6-week able nesting cover, mechanically destroy season if each pair used a territory for early nests, and increase predation on only 2 weeks. nests and on the nesting hens themselves My data suggest that variation in (Johnson and Sargeant 1977). nesting dates by individual pairs ac In the present mallard nesting en counts for much of the variation ob vironment there may now be selection served in the field. Humburg et al. (1978) against early nesters as early nesting observed several marked pairs of mal hens contribute less to the gene pool. The lards that were resident and delayed wide range of individual variation breeding for several weeks past initiation evident in mallards provides a gene pool by most pairs. Such studies need to be potentially responsive to directional done in other parts of the continental selection. Although not common, mas breeding range to refine current survey sive shifts in gene frequencies have been techniques. recorded in wild populations of several The wide span of nesting dates and other animals (Mayr 1963:145). The best clutch size, along' with the consistency known case is that of industrial melan demonstrated by individual pairs, indi ism in the Lepidoptera (Kettlewell 1961). cate the existence of considerable genetic A similar shift in significant characteris variation in wild mallard populations. tics in the gene pool is implied in the pink This is characteristic of every natural salmon (Oncorhynchus qorbuscha) and 99 INDIVIDUAL VARIATION IN MALLARDS the Canada goose (Branta canadensis), potential would have important impli although these cases are somewhat con cations for management. founded by other factors such as learn ing and tradition. Early salmon runs CONCLUSION were markedly reduced as a result of greater harvest pressure, but later runs Waterfowl biologists are primarily thrived under season closures actually concerned with population responses intended to preserve the whole stock that result from management activities. (Vaughan 1947). Raveling (1978) con An understanding of the cause-and cluded that extermination of certain effect relationships of these responses Canada goose flocks was the result of cannot necessarily be gained by analysis over-harvest while other flocks thrived at the population level. Population para under protection. That the apparent meters are the measured responses of a selection against early nesters could sample of individuals, each of which has change the genetic composition of the a unique complement of characteristics continental mallard population is specu from the gene pool. An understanding of lation. However, management and re the needs and strategies of individuals search should be aware of this pos should be a central focus for research on sibility, because a changing recruitment managed wildlife populations. 100 WATERFOWL AND WETLANDS SYMPOSIUM LITERATURE CITED ANDERSON, D. R., AND K. P. BURNHAM. Wetlands Seminar. Can. Wild\. Servo 1976. Population ecology of the mallard: Rept. Ser. 6. the effect of exploitation on surviva\. U.S. __ . 1969b. Assessing breeding popula Fish Wild\. Servo Resour. Pub\. 128. 66pp. tions of ducks by ground counts. Pages ANKNEY, C. D., AND A. R. BISSET. 1976. 178-230 in Saskatoon Wetlands Seminar. An explanation of egg-weight variation Can. Wild\. Servo Rept. Ser. 6. in the lesser snow goose. J. Wild\. Manage. GATES, J. M. 1962. Breeding biology of the 40(4):729-734. gadwall in northern Utah. Wilson Bull. BATT, B. D. J. 1976. Reproductive parameters 74(1):43-67. of mallards in relation to age, captivity GILMER, D. S., 1. J. BALL, L. M. COWAR and geographic origin. Ph.D. Thesis. DIN, J. R. REICHMANN, AND J. R. Michigan State Univ., East Lansing. TESTER. 1975. Habitat use and home 50pp. range of mallards breeding in Minnesota. __ , AND H. H. PRINCE. 1978. Some J. Wild\. Manage. 39(4):781-789. reproductive parameters of mallards in GRICE, D., AND J. P. ROGERS. 1965. The relation to age, captivity and geographic wood duck in Massachusetts. Massachu origin. J. Wild\. Manage. 42(4):834-842. setts Div. Fish. Game, P-R Rep., Proj. __ , AND __ . 1979. Laying dates, W-19-R. 96pp. clutch size and egg weight of captive HUMBURG, D. D., H. H. PRINCE, AND R. A. mallards. Condor 81(1):35-41. BISHOP. 1978. The social organization BECKER, W. A. 1967. Manual of procedures of a mallard population in northern Iowa. in quantitative genetics. 3rd ed. Washing J. Wild\. Manage. 42(1):72-80. ton State University, Pullman. 170pp. JOHNSGARD, P. A. 1973. Proximate and BELLROSE, F. C. 1976. Ducks, geese and ultimate determinants of clutch size in swans of North America. Stackpole Anatidae. Wildfowl 24:144-149. Books, Harrisburg, PA. 544pp. JOHNSON, D. H., AND A. B. SARGEANT. __ , K. L. JOHNSON, AND T. U. MEY 1977. Impact of red fox predation on the ERS. 1964. Relative value of natural sex ratio of prairie mallards. U.S. Fish cavities and nesting houses for wood Wild\. Servo Res. Rep. 6. 56pp. ducks. J. Wild\. Manage. 28(4):661-676. KETTLEWELL, H. B. D. 1961. The phenome CALVERLEY, B. K., AND D. A. BOAG. 1977. non of industrial melanism in Lepidop Reproductive potential in parkland and tera. Ann. Rev. Entomo\. 6:245-262. arctic-nesting populations of mallards LEE, F. B., AND A. D. KRUSE. 1973. High and pintails (Anatidae). Can. J. Zoo\. survival and homing rate of hand-reared 55(8):1242-1251. wild-strain mallards. J. Wild\. Manage. COOPER, J. A. 1978. The history and breed 37(1):154-159. ing biology of the Canada geese of Marshy LYNCH, J. J. 1964. Weather. Pages 283-292 Point, Manitoba. Wild\. Monogr. 61. 87pp. in J. P. Linduska, ed. Waterfowl tomor COULTER, M. W., AND W. R. MILLER. 1968. row. U.S. Government Printing Office, Nesting biology of black ducks and mal Washington, D.C. lards in northern New England. Vermont MAYR, E. 1963. Populations, species and Fish Game Dept. Bul\. 68-2. 74pp. evolution: an abridgement of animal DANE, C. W. 1966. Some aspects of breeding species and evolution. Harvard Univer biology of the blue-winged tea\. Auk sity Press, Cambridge, MA. 453pp. 83(3):389-402. McKINNEY, F. 1973. Ecoethological aspects DZUBIN, A. 1969a. Comments on carrying of reproduction. Pages 6-21 in D. S. Far capacity of small ponds for ducks and ner, ed. Breeding biology of birds. Na possible effects of density on mallard tional Academy of Sciences, Washington, reproduction. Pages 138-160fn Saskatoon D.C. 10J INDIVIDUAL VARIATION IN MALLARDS MENDALL, H. L. 1958. The ring-necked duck tions. Trans. N. Am. Wild\. Conf. 13:57 in the northeast. Univ. Maine Bul\. 16. 69. 317pp. STOTTS, V. D., AND D. E. DAVIS. 1960. The MORSE, T. E., J. L. JAKOBOSKY, AND V. P. black duck in the Chesapeake Bay of McCROW. 1969. Some aspects of the Maryland: breeding behavior and biology. breeding biology of the hooded mergan Chesapeake Sci. 1(3/4):127-156. ser. J. Wild\. Manage. 33(3):596-604. TRAUGER, D. L. 1971. Population ecology of POSTON, H. J. 1974. Home range and breed lesser scaup (Aythya affinis) in subarctic ing biology of the shoveler. Can. Wild\. taiga. Ph.D. Thesis. Iowa State Univ., Serv.Rept.Ser.25.49pp. Ames. 118pp. . RAVELING, D. G. 1978. Dynamics of distri bution of Canada geese in winter. Trans. VAUGHAN, E. 1947. Time of appearance of N. Am. Wild\. Nat. Resour. Conf. 43:206 pink salmon runs in southeastern Alaska. 225. Copeia 1(1):40-50. SELLERS, R. A. 1973. Mallard releases in WARD, P., AND B. D. J. BATT. 1972. Prop understocked prairie pothole habitat. agation of captive waterfowl: the Delta J. Wild\. Manage. 37(1):10-22. Waterfowl Research Station system. SOKAL, R. R., AND F. J. ROHLF. 1969. Bio Wildlife Management Institute, Washing metry. W. H. Freeman and Co., San ton, D. C. 64pp. Francisco. 776pp. WILLIAMS, G. C. 1966. Adaptation and SMITH, R. H., AND A. S. HAWKINS. 1948. natural selection. Princeton University Appraising waterfowl breeding popula Press, Princeton, NJ. 307pp. 102 WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977 Symp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979 BIOENERGETICS OF POSTBREEDING DABBLING DUCKS I HAROLD H. PRINCE Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan 48824 Abstract: The postbreeding activities of dabbling ducks are evaluated in terms of energy and time allocation. Although limited data are available for the postbreeding period, the allometric relationship between body weight and basal metabolic rate (BMR)can serve as a basis for under standing energy metabolism. Laboratory estimates of the BMR of mallards (Anus platyrhyn chos) and increments for maintenance, activity, thermoregulation, and free-living conditions are presented. It is proposed that seasonal variation in energy consumption is relatively stable and amounts to 3x to 4x BMR. Stability is achieved during periods of increased energetic demands by behavioral modifications that result in the conservation of energy. Use-days based on esti mated energy expenditures and amounts of available food can be calculated to estimate the carrying capacity of specific areas for dabbling ducks. Postbreeding activities for North Unsuccessful females may accompany American waterfowl species belonging to the drakes to molting areas (Gilmer et al. the Tribes Cairinini and Anatini are 1977). The molt migration has been similar. Hochbaum (1944) outlined the described as a movement from the breed major events during this period at the ing place to a special molting area that is Delta Marsh in Manitoba. Although the common to a large number of birds. activities of all species are not as well Hochbaum (1944) described the molting understood as those during the breeding areas of dabbling ducks in Manitoba as period, we know that all species undergo large, permanent marshes. the prebasic molt prior to fall migration Salomonsen (1968) pointed out that the and wintering. Males of most species per selective advantage of the molt migra form a molt migration while females tion could be the reduction in competi that successfully nest usually stay on the tion for food between adult males and/ breeding areas with the ducklings or nonbreeders, and the female and (Salomonsen 1968, Gilmer et al. 1977). ducklings. In North America postbreed- IMichigan Agricultural Experiment Station Journal Article Number 9102. 103 BIOENERGETICS OF POST BREEDING DABBLING DUCKS ing activities have been described by of these methods require untested Wetmore (1921), Munro (1943), Hoch assumptions concerning their relation baum (1944, 1955), Sowls (1955), Oring ship to the energetic costs of a free-living (1964), Grice and Rogers (1965), Coulter bird. Although all these methods can and Miller (1968), Bellrose (1976), and provide useful data, thermal and behav Gilmer et al. (1977). ioral models such as the one presented by The change in waterfowl behavior Owen and Reinecke (1979) in this sympo from the widely spaced breeding birds to sium must be developed before a more the gregarious molting, migrating, and rigorous understanding can be achieved. wintering groups marks a change in the factors that affect survival and fitness. This has been recognized by hunters and Basal Metabolic Rate waterfowl managers, and techniques to provide food as an attractant are com The metabolic rate of an animal in a monly practiced throughout North thermoneutral zone, at rest, and in a America. Although techniques to attract postabsorptive state has been defined as postbreeding migrant and wintering the basal metabolic rate (BMR) (King birds are successful, the specific needs of 1974). King (1974) pointed out that each species are not well understood. standard metabolic rate (SMR) was An analysis of both time and energy allo originally synonymous with BMR, but cation is needed to understand the re has since been confused with fasting quirements of the postbreeding stages of metabolic rate (FMR) andresting meta the life cycle. This is necessary to eval bolic rate (RMR). He concludes that BMR uate the true impact of management is the only measure that has retained a recommendations and practices on dab clear definition. BMR is strongly weight bling ducks. This paper will review the dependent, and can be expressed by the energy conserving and energy demand equation: ing processes of energy expenditure for post breeding dabbling ducks. where M is a metabolic parameter, a is a ENERGY BUDGETS constant, W is body weight, and b is an exponent. This relationship has been Methods further refined by Aschoff and Pohl (1970), who reported that the metabolism The goal in the analysis of energy of fasted birds in a darkened respiratory expenditures is to estimate the cost of chamber has a measurable diurnal various metabolic activities in free-living rhythm. The metabolic rate during the birds. King (1974) reviewed the methods activity phase of the cycle was about 25% that have been used to estimate energy higher than during the resting phase. expenditures including laboratory mea They proposed that the equation express surements of oxygen consumption, ing the relationship between body weight metabolizable energy intake (ME), and and metabolic rate should be computed time-energy analyses of free-living birds. separately for the rest and activity Energy expenditures of free-living birds phases of the diurnal cycle. King (1974) can be calculated directly by quantifying calculated an equation for nonpasserines their activities in caloric terms or by at rest based on Aschoff and Pohl's equa using indirect measures such as body tion to be kcal/h == 3.60 WO.734 where W weights or analysis of crop contents. All is body weight in kg. He considered this 104 WATERFOWL AND WETLANDS SYMPOSIUM to be the best estimate of BMR. BMR greatest in the early part of the run and can be used to formulate energy budgets decreased with time. if rates of energy expenditure for various Incubating females were restricted to activities are considered as multiples of their nest boxes at least 18 h prior to the BMR (King 1974). run and then 02measurements were Other indirect estimates of BMR are made for 36 h. The straw and down from needed to evaluate the applicability of the nest box and the original number of Aschoff and Pohl's equation estimating eggs containing dead embryos were BMR to dabbling ducks. Although there placed in the respiratory chamber with are no data for postbreeding birds, I have the female. One of the six females ac collected data on the diurnal cycle of tively incubated her clutch of eggs while in the respiratory cham ber. Oxygen 2.• 'I[I'E£DIIIC consumption remained constant at about DAY IiIIGHT DAY illiCit' 1.0 cc 02/h for the first 20 h (Fig. 2). Oxy I.' <," -.:: .. I.• :: ... :: .., ,. It U Fig. 1. Metabolic rates of prebreeding male 121&20244.,,1t2024 and female mallards at 25C for a 28·h period TI.I lid expressed incc02/g/h. Fig. 2. Metabolic rates of incubating female mallards fasted for 18 h at rest in a mallards at 30 C for a 40-h period expressed darkened metabolic chamber at a ther incc02/g/h. moneutral temperature (Prince unpub gen consumption increased significantly lished). Techniques for measurement of on the morning of the second day, de oxygen consumption are presented in creased to a low point at 1600 h, and Hill (1972).Three female and 3 male mal increased prior to sunset. lards in the prebreeding chronological Although 02 consumption did fluctuate stage (late April) and 6 females that had among individuals, Prince (unpublished) been incubating eggs from 18 to 22 days did not observe the diurnal cycle in pre were monitored for 28 and 40 h, respec breeding mallards that Aschoff and Pohl tively. (1970) reported for bram blings (Fringilla. The pattern of oxygen consumption for montigringillu). This is a period of the prebreeding birds was similar among year when a great deal of nocturnal acti individuals (Fig. 1). Their initial con vity occurs. The diurnal cycle was ap sumption was above 1.0 cc 02/h when parent for the incubating females when they were placed in the chamber in the the 02 consumption increased on the early evening. Oxygen consumption morning of the second day of the experi declined throughout the night to about mental run. More data are needed for 0.8 cc 02/h and remained at a constant mallards as well as other species to deter level throughout the following day until mine the nature of the metabolic cycle. the run was terminated. Variability was Because body weight and metabolic 105 BIOENERGETICS OF POSTBREEDING DABBLING DUCKS rate were measured in my study, the mic action - SDA) occurs during the constant a can be calculated. A compari process of digestion and molecular trans son of the a value of the predictive equa formation of foodstuffs into chemical tion and the computed a value from my states. data should give some indication of the The concept of productive energy (PE) applicability of Aschoff and Pohl's equa developed by Kendeigh (1949) and re tion to mallards as well as its value as a cently summarized by Kendeigh et al. base for an energy model. I examined the (1977) is basic to understanding the bio data for pre breed ing and incubating energetics of birds. This concept has been birds and selected the lowest rate of 02 reviewed by Ricklefs (1974), who sum consumption for a 30-min period. These marized the relationship between values were then converted to kcal per productive energy (available energy Table 1. The a values calculated from the equation M =a W b where m=kcal per day, a =con stant, and Wb weight to the 0.734 power. The a values (x + SE)are from the 3 lowest metabolic readings for male and female mallards prior to breeding and incubating females. The chamber temperatures were 25 and 30C for pre breeding and incubating birds, respectively. Female Male Chronological n Value n Value stage Pre breeding 3 85.3 ± 3.4 3 88.4 + 1.0 Incubation 6 88.9 ± 4.5 Pooled value 87.9 ± 2.3 day with a respiratory value of 0.8, and minus existence energy) and ambient solved the equation M=a W for a. There temperature (Fig. 3). Existence energy were no significant differences among (EE) is the energy needed by the animal the calculated a values for pre breeding to stay alive; it includes basal metabo females, males, and incubating females lism, SDA, foraging activity, and tem (Table 1). The pooled value of 87.0 + 2.3 perature regulation. PE is the portion (SE) for a is not different from the value available for productive processes. For of 86.4 for nonpasserines at rest. The As post breeding waterfowl this would in choff and Pohl equation appears to be a clude molt and migration. Most winter good estimator of BMR for mallards and ing activity could be included under the possibly other species of dabbling ducks. EE category. Available energy (AE) has been defined as the maximum rate at Energy Expenditure which energy can be metabolized by the bird, which is a function of the quantity Many models have been developed to and quality of food (Ricklefs 1974). Ken depict the energy partitioning process. deigh (1949) suggested this could be esti Brody (1945) developed the basic model mated from the metabolic rate of an for the energetics of production in individual maintaining weight but sub domestic animals. Various foods yield jected to maximum cold stress. Esti different quantities of metabolizable mates of AE for house sparrows (PU1Jser energy (ME). The net or available energy domesticus) have been made by observ is the quantity that remains after the ing the lowest temperature that 50% calorigenic effect of food (specific dyna (LD 50) of newly caught, locally-acclima 106 WATERFOWL AND WETLANDS SYMPOSIUM ample of cold tolerance does not negate the value of the AE concept, it does mean that equipment is a problem and some other standardized procedure is needed. E The highest rate of food consumption VI by a bird under laboratory condition o ..c provides an estimate of the limit of AE. c For mallards, laying females consistent Q) ~ ly consume the greatest quantities of food. Energy requirements for female mallards laying at varied rates are pre sented in Table 2. The energy needs ad justed to a rate of lay of 1 egg per day Tc ranged from 339 to 389 kcaJ/bird/day. Temperature Purol (1975) reported that female mal lards held outdoors and fed a commercial Fig. 3. The relationship between ambient breeder chow metabolized approximately temperature and productive energy (available 405 kcallbird/day during peak egg pro energy minus existence energy) when TB= duction in May when ambient tempera body temperature, Tc=lower critical tem tures were about 13 C. Although this perature, and TL=upper and lower tempera value would include some of the free ture limits of long-term existence (From Rick lefs 1974: 173). living energy costs, the birds could not fly; the estimate is, therefore, conserva tized birds could survive and then solving tive because the birds did not lose weight. the EE equation for energy. This pro Based on these data a value of 450 kcall cedure is difficult to do and it is unlikely day should be used as the best estimate that many estimates of AE for dabbling of AE for mallards. ducks will be made based on cold toler If the BMR as well as the cost of ther ance. For instance, Giaj a and Males moregulation can be estimated for a (1928, in Brody 1945:284) found that a species, then the cost of some of the pro mallard in a postabsorptive state was ductive processes can be compared to the able to maintain body temperature for AE. Although estimates of the energetic Ih at -lODe. Although this extreme ex costs of certain activities can be ex- Table 2. Estimated energy requirements of mallard females laying 1 egg/day based on metabo lized energy consumption by caged females at varied rates of lay. Total needs were estimated on a metabolic cost of 157kcal per egg produced (PuroI1975). Energy needs Location Metabolized energy Rate of lay adjusted to 1 egg/day Study of bird (kcall bird/day) (no./day) (kcallbird/day) Purol (l975) Michigan 289 0.68 339 (indoors) Foster (1976) Manitoba 265 0.33 370 (indoors) Foster (1976) Manitoba 330 0.62 389 (outdoors) Holm and Scott (1954) New York 325 0.69 373 (outdoors) 107 BIOENERGETICS OF POSTBREEDING DABBLING DUCKS pressed as an increment of BMR (King ological periods. The values can be 1972, 1974), this can lead to confusion standardized by solving for a in the when applied to behavioral data that can equation M =aW (Table 3). Although the be observed and measured for free-living values of a range from 100.1 to 134.5, individuals. This happens because there there are no significant differences is an overlap and at times an interaction between sex or chronological periods. The between the existence and productive pooled value of a is 114.3 ± 3.3 (SE), categories (e.g., foraging and courtship which is 1.3x above a value computed as activities). The existence activity takes the coefficient for the BMR of mallards. precedence over the productive category. This is similar to a difference of 1.24x Thus, the cost of thermoregulation be between the resting and activity phases comes a base for an energy model. These of the daily cycle for passerines and non costs are usually met when BMR·incre passerines reported by Aschoff and Pohl ments are considered. Increments of (1970). This is the best estimate of mini BMR can be useful for establishing a mum energy expenditure of birds that dimension among food resources, clima are awake, and it probably more nearly tic factors, and waterfowl numbers and represents the minimum metabolic rate activities that occur on specific areas. of free-living mallards. Although there are no significant dif ferences in the calculated a values, some ENERGETIC INCREMENTS different trends in the a values between Maintenance sexes were apparent. The largest dif ference in the values occurred for fe Maintenance has been defined by King males and the largest variation about the (1974) as the increase in metabolic rate means was recorded for males. The a resulting from neuromuscular tonus and value of birds in the pre basic molt was the physical activity associated with the largest for both sexes, which suggests wakefulness. I have measured the fasting that the metabolic rate of birds under metabolic rate of mallards in a darkened going molt may be slightly elevated. metabolic chamber at a thermoneutral Locomotion temperature of 30 C. Three birds per sex were measured over five different chron Tucker (1973) reviewed the theoretical Table 3. The a values calculated from the equation M=aWbwhere M=kcal per day, a=con stant and Wbweight to the 0.734 power. The a values (x ± SE) are from 6 metabolic readings between 3 to 4 h after the start of the run for male and female mallards at 5 chronological stages at a thermoneutral temperature of 30 C (n=3). Chronological stage Female Male Winter 100.1 ± 3.7 111.5 ± 12.1 Pre breeding 116.2 ± 9.3 108.4 ± 3.7 Laying e 121.9 + 2.0 111.0 ± 8.0 Incubation-' 107.6 ± 4.4 110.1 ± 14.2 Molt 134.5 + 17.3 121.1 ± 18.1 Pooled value 114.3 ± 3.3 a Male paired with laying or incubating female. 108 WATERFOWL AND WETLANDS SYMPOSIUM aspects of the energetics of flight. Hart as a complete pre basic molt just after and Berger (1972) empirically analyzed breeding, followed by the basic or eclipse the cost of flight and computed the equa plumage, and then another partial or tion kcallh = 45.5W 0.73 where W = kg. prealternate molt that results in the Tucker (1970, 1973) calculated an equa alternate or breeding plumage. The pat tion estimating energetic costs that tern of molt for adult females is more according to King (1974) is not statisti confused because both plumages are cally different from the Berger-Hart similar. Although there is some variation equations. Tucker's estimate is kcallh= in terminology, females undergo a com 44.7WO.78 where W=kg. plete molt in the summer, after breeding, The estimated costs of flight for a 1.1 and another partial molt the following kg mallard calculated with the Berger spring prior to the breeding season. Hart and Tucker equations are 49 and 60 The energetics of molt for postbreed kcallh, respectively. This is a rate of ing waterfowl are not well understood. 12.4x and 15.3x BMR, or between 2 and The process places a number of nutri 3 times more than the AE estimate of 450 tional and energetic demands upon the kcallday. Raveling and LeFebvre (1967) individual. According to King (1974), a recommended 12x BMR be used when l-kg bird will have to synthesize about energetic demands of long range flight 64 g dry weight of feathers. In addition, are considered. For long distance flights there are cardiovascular demands caused stored energy obviously must be used. by growing feathers as well as a potential A flying time of 2 to 3 h/day would also for extra thermoregulatory costs. Al make an energetic demand comparable though King (1974) cited four studies to egg production. King (1974) estimated that reported higher 02 consumption by that the flight range of a l-kg bird would molting birds when contrasted with non be from 1,800 to 3,800 km with a 25 to molting individuals, Prince (unpublished 50% body mass loss when fat is used as data) could find no significant increases fuel. in the amount of 02 consumed by male or Swimming is another form of locomo female mallards that were growing new tion for which there are some estimated remiges. Prince's (unpublished data) energetic costs. Prange and Schmidt results on mallards were similar to those Nielsen (1970) measured the metabolic of Davis (1955) and West (1968) on caged cost of swimming for mallards. They birds that suggested no net increases in estimated 02 consumption to be 2.2x the caloric cost. If this is true, a modification resting metabolic level for birds swim of behavior would be required to offset ming at moderate speeds and 4.1x the the energetic cost of molting. resting metabolic level at maximum sus General descriptions of waterfowl tainable speed. When these estimates are activities during molt suggest there are contrasted to predicted BMR they are specific ecological requirements. Weller 3.2x and 5.7x BMR (King 1974). Observa (1976) pointed out that the birds seek tions of swimming ducks suggest that food-rich water areas during the molt they swim at rates that optimize the cost periods. During the flightless period of transport (Prange and Schmidt-Niel mallards and other dabbling ducks fre sen 1970). quent areas with dense cover (Munro 1943, Hochbaum 1944, Raitasuo 1964). Molt For mallards there is a large individual variation for the date of molt within The Anatini have at least two body sexes (Raitasuo 1964). In addition, males plumages per year. Weller (1976) ou t molt 2 to 3 weeks before females (Hoch lined the general pattern for adult males baum 1944, Boyd 1961, Lebret 1961, Rai 109 BIOENERGETICS OF POSTBREEDING DABBLING DUCKS tasuo 1964). Gilmer et al. (1977) found only species of Anus for which there are that drake mallards and some unsuccess enough data to begin to understand the ful hens left the breeding areas in north effects of low temperature on energetics. western Minnesota by early summer and For fasted mal1ards metabolism begins that about one-half of the successful hens to increase below the lower critical tem remained on the breeding areas and perature range of 18 to 25 C at a rate of molted. The pattern appears to be to 2.6 kcall WOo 734/ day for each degree of maximize variation among individuals decrease (Prince, unpublished data). Al during molt which does reduce intra though Wooley and Owen (1977)reported specific competition. It is not clear if a similar pattern for black ducks, the breeding and brood marshes meet the lower critical temperature ranged from specific needs of postbreeding mal1ards 8 to 14 C, which is about 10 C below that (Gilmer et al. 1977). for mallards, and the rate of heat produc The ecological needs of dabbling ducks tion below the lower critical temperature during the molt period require more ranged from 2.7 to 3.8 kcallbird/day, study. Presently, our waterfowl manage which is higher than that for mallards. ment strategies do not encompass this When temperature is considered as a period when birds may have require multiple of BMR, then the effect on the ments as complex as those during the mal1ard can be expressed as (2.06 - 0.03T) breeding period. x BMR where T=C. Thus, at 0 C a mal lard will increase metabolic rate above Climatic Factors basal by 2.1x and by 2.7x at -20 C. Al though these estimates include heat loss Although a general inverse relation through the feet, a study by Kilgore and ship between temperature and metabolic Schmidt-Nielsen (1975) on mallards rate is wel1 documented for birds (Ken showed that heat loss through the feet deigh 1969, King and Farner 1961, King becomes more important at low tempera 1974, Ricklefs 1974), the response of tures. They found that loss of heat from individual species will vary with size, feet was 3 to 7% of the simultaneous thermal conductance of plumage, and metabolic heat production between 0 and thickness of subcutaneous fat. For exam 20 C and the rate doubled below 0 C. ple, Owen (1970) estimated that outdoor Freeman (1971) stated that sensible existence energy of blue-winged teals heat exchange between the body and' the (Anus discors) during the fal1, winter, environment occurs primarily by radia and spring increased by 1.7 kcallbird/ tion and convection. The impact of solar day/degree C of decrease. Prince (unpub radiation on metabolic rates needs to be lished data) estimated that mallards will evaluated, because the zone of thermo need to produce an additional 2.6 kcall neutrality could be depressed on cold, bird/day/degree C of decrease. The sunny days. Conduction is also important metabolic body weight (WO,734) of blue because heat loss through the feet can be winged teals is 50% that of mallards, significant at low temperatures. This which is similar to the 65% difference in explains why the typical response of a the rate of heat loss. mal1ard to low temperatures is to reduce Temperature and/or wind velocity activity and rest on ice or land with its begins to have an observable effect feet tucked up against the abdomen beyond the thermoneutral zone. Sensible (Raitasuo 1964,Reed 1971). heat exchange will be affected by phys iological and behavioral adjustments Free-living Conditions that are made by the bird. The mallard and black duck (Anus rubripes) are the The energetic demands on postbreed 110 WATERFOWL AND WETLA~DS SYMPOSIUM ing dabbling ducks are diverse and, at his estimate of 431 kcallbird/day (4.6x times, demanding. The energy needed for BMR) as the cost of egg laying and free maintenance during migration and existence. periods of climatic stress during the win ter might approach energetic demands of Biological Factors breeding. King (1974) suggested that the daily Several physiological and behavioral energy expenditure (DEE) in birds and processes affect survival during periods mammals is an allometric function of of climatic stress. Prince (unpublished body weight. This means that energetic data) did not find a difference in meta costs for DEE of dabbling ducks can be bolic rates of mallards as a function of estimated on the basis of their body season. This implies that insulative weight. Values of DEE range from 1.5x covering and/or BMR of mallards to 4.0x BMR for nontorpid, free-living throughout the year is the same. This homeotherms; the average for birds is does not seem to be the case for black 3.5x BMR (King 1974). These values are ducks as evidenced by individual birds very general and include energy output acclimated to 19 C producing more heat for maintenance, maintenance of social than those acclimated to 5 C (Wooley and structure, and reproduction. Owen 1977). Although King (1974) indicated that Body weights of mallards fluctuate energy expenditures by free-living birds seasonally (Fig. 4). In England, Owen outside the breeding season are un and Cook (1977) recorded the highest known, he cited Dolnik (1971), who sug @- Folk et at 1966 "- 0 ••" and Cook 1971 gested that an energy utilized by a hypo o Male thetical migratory bird might balance o Female out to be fairly stable through the year. This may be the case for dabbling ducks if the cost of egg production for nesting females is excluded, Owen (1970)showed that metabolized energy of captive blue winged teals was fairly stable through out the year. Purol (1975) reported that the energy intake by a group of 35 male mallards held in an outdoor pen was fairly stable through the year at about MONTH 240 kcallbird/day, or about 2.5x BMR. If the additional demand of 1 h of flight per Fig. 4. Body weights of male and female day were included for the captive birds, mallards by month. another 50 to 60 kcal should be added to weights for males between October and the estimate, yielding 280 to 290 kcall December and for females between bird/day (1.1 kg body weight) or at 3.0x November and January. Although Folk BMR. This seems to be a realistic esti et al. (1966) reported a similar seasonal mate for the DEE of free-living mallards weight pattern in Czechoslovakia, these at intermediate (0-20 C) temperatures data are more variable and show a 10 to during the postbreeding period. This does 12% reduction in weight of both sexes not consider the cost of migration. The between December and January. Owen estimate is lower than the estimate of (1970) reported a similar weight cycle in 3.6x BMR that Purol (1975) made for a captive blue-winged teals. female laying an egg per day (Table 2) or Owen and Cook (1977) reported that III BIOENERGETICS OF POSTBREEDING DABBLING DUCKS the condition index (defined as weight! hunting (Pulliainen 1963, Moilanen 1971, wing ratio expressed as g/cm) of mal Reed 1971, Sugden et al. 1974,Cooper and lards was highest during the winter Johnson 1977). A characteristic of all months. The pattern is similar for blue northern wintering flocks is a preponder winged teals (Owen 1970). This implies ance of males, suggesting that females that there is a physiological adaptation are not capable of doing as well in these for mallards and blue-winged teals to environs. Smith and Prince (1973) ob build up body reserves prior to periods of served such a pattern between sexes for cold stress. It would not be surprising for fasting metabolism of mallards. A simi similar patterns to exist for other dab lar pattern has been reported in the bling duck species. stress response of green-winged teals The condition of mallards can also (A nas crecca) wintering on the high vary between years on a wintering area. plains region of Texas (Bennett and Owen and Cook (1977) observed dif Bolen 1978). More research of the meta ferences in body conditions of mallards bolic and physiological response of dab wintering in England that were corre bling ducks to climatic stress might give lated with the amount of cereal grain additional insight to the problem of un available on stubble fields. They sug balanced sex ratios. gested that these differences affect win Body weights of dabbling ducks indi ter survival as well as the ability to breed cate energetic capabilities and needs the following summer. (Fig. 5). All species are dimorphic; males Behavioral changes in mallards occur during periods of climatic stress. Reed (1971) observed activities of 6,000 to 8,000 ~~:i "~:IA" 1200 mallards wintering in southeastern ... - MALE F - FEMALE lIDO Af AF Michigan and described a number of A - AOULT "8LACltiF changes in daily activities that were ! - IMMATURE 1000 9~ associated with both wind and tempera A"l1M 'ADwm AM... ture. These included a reduction of daily 900 AF llill! WIb:EON feeding flights to 1 per day contrasted AF ~ 000 ~~IFIF IM1 with 2 per day during the fall period as W'(q) AF WOOD reported by Bossenmaier and Marshall 100 IF ~ (1958) and Winner (1959). Reed (1971) ::I'F::'! also noted that the birds reduced the 000 IF := NDRTHERN duration of feeding flights as the mean ~ 3-day temperature decreased; most of the 000 additional time was spent sitting near water. Rather than increasing foraging activities during periods of extreme cli matic stress, mallards reduce their activities and depend on body reserves. Fig. 5. Fall body weights of dabbling ducks by Owen and Cook (1977)reported that win age and sex (data from Bellrose 1976). tering mallards in England emigrated during long periods of unfavorable are heavier than females and adults are weather. heavier than immatures, based on fall Investigators studying mallards on the weights reported by Bellrose (1976). The northern edge of the wintering range heavier males would require more energy describe their major needs as available than females and they would also be bet food, open water, and protection from ter able to withstand. climatic stress by 112 WATERFOWL AND WETLANDS SYMPOSIUM virtue of their larger body size conferring 4. Although these values would be the an advantage of endurance (Calder 1974). best to use for dabbling ducks, estimates This differential could be a factor that of the ME can also be obtained from contributes to disparate sex ratios favor work done on domestic birds (Scott et al. ing males, which has been observed in 1969). Estimates of physiological require dabbling ducks (Bellrose 1976). The win ments can be based on the activity incre ter distribution of dabbling ducks ments of BMR that have been previously reported by Bellrose (1976) from north to discussed (Table 5). These values then Table 4. Metabolizable energy (ME) of food items for mallards. Food item ME (kcal/g dry matter) Reference Wheat 3.53 Sugden (1971) (Triticum spp.) Barley 3.17 Sugden (1971) (Hordeum vulgare) Fall rye 3.34 Sugden (1971) (Secale cereale) Proso millet 3.57 Purol (1975) (Panicum miliaceum) Soldierfly larvae 2.39 Purol (1975) (Stratiomys spp.) Duckweed 1.43 Purol (1975) (Lemnaminor) Cellulose 0.20 Purol (1975) south is similar to the weight distribu can be combined with the estimate of tion. Mallards and black ducks are BMR based on body weight in order to species with the more northern distribu estimate the amount of energy needed by tion, whereas the teal species occur the the bird. Use-days then can be calculated farthest south. Although many other according to the equation: factors affect winter distribution of dab bling ducks, body size does give an indi Use-days cation for closely related species of the ME of Food (kcal/g) physiological capability to withstand (birds/days/ha) - x Yield (g/ha) climatic stress. Energy Needs (kcal/bird/day) ENERGYRESOURCES Crop yield data must be converted to a Use-Days dry weight value for inclusion in the equation. Use-days then can be used to Food consumption is influenced by better understand the relationship many factors. Although nutrition is very between the maximum number of birds important, especially during breeding, using a particular habitat and the capac this discussion will be limited to energy, ity of that area to support the population. which appears to be the most dominant ecological factor during the post breeding Environmental-Energy Resource period. Values of ME of plant and animal Interactions foods for mallards are presented in Table Although egg production and time 113 BIOENERGETICS OF POSTBREEDING DABBLING DUCKS Table 5. Summary of activity levels and energetic capabilities applicable to postbreeding dabbling ducks as multiples of BMR. Activity xBMR Reference Maintenance 1.3x Prince (Unpublished) Swimming resting 3.2x Prange and Schmidt-Nielsen (1970) maximum 5.2x Prange and Schmidt-Nielsen (1970) Flying 12.4x - 15.3x Hart and Berger (1972),Tucker (1973) Temperature (C) 10 1.8x Prince (Unpublished) 0 2.1x Prince (Unpu blished) -10 2.4x Prince (Unpublished) -20 2.7x Prince (Unpublished) Molt 1.3x Prince (Unpublished) Free-living range 1.5x - 4.0x King (1974) birds 3.5x King (1974) fall mallards 3.0x Prince (Unpublished) Available energy (daily) 5.0x Prince (Unpublished) spent in flight have been identified by breeding energetic demands as are the Owen and Reinecke (1979:84) in this males. symposium as the most energetically Dabbling ducks are best adapted for a demanding activities during the breeding climate above 0 C. Although they do win season, the emphasis shifts to molting, ter in areas where temperatures are flight, swimming, and thermoregulation lower, the energetic demands increase during the other parts of the year. Much rapidly, and behavioral and physiological of the selection pressure to maximize adjustments are made that result in the fitness with respect to energy during the conservation of energy. The range of the breeding season is focused on the female, DEE appears to be between 3x and 4x whereas the selection pressures for the BMR. As the DEE approaches 4x BMR remaining part of the year appear to be the likelihood of mortality would appear similar for both sexes. With the intense to increase as well as the potential to selection pressures being focused on the reduce the condition of the bird and the female during the breeding season, a dif ability to breed the following spring. ferential response by sex might occur Research on the impact of winter activi during the rest of the year, and females ties on the reproduction is needed to ob might not be as well adapted to the post- tain additional insight into the manage ment of postbreeding dabbling ducks. 114 WATERFOWL AND WETLANDS SYMPOSIUM LITERATURE CITED ASCHOFF, J., AND H. POHL. 1970. Rhyth Physiology and biochemistry of the mic variations in energy metabolism. domestic fowl. Vol. 2. Academic Press, Fed. Proc. 29:1541-1552. New York. BELLROSE, F. C. 1976. Ducks, geese and GIAJA, J., AND B. MALES. 1928. Sur la swans of North America. Stackpole valeur du metabolisme de base de qual Books, Harrisburg, PA. 544pp. ques animaux en function de leur surface. BENNETT, J. W., AND E. G. BOLEN. 1978. Ann. Physiol. Physiochem. BioI. 4:875 Stress response in wintering green 904. winged teal. J. Wildl. Manage. 42(1):81-86. GILMER, D. S., R. E. KIRBY, I. J. BALL, AND J. H. RIECHMANN. 1977. Post BOSSENMAIER, E. F., AND W. H. MAR breeding activities of mallards and wood SHALL. 1958. Field-feeding by waterfowl ducks in north-central Minnesota. J. in southwestern Manitoba. Wildl. Wildl. Manage. 41(3):345-359. Monogr. 1. 32pp. GRICE, D., AND J. P. ROGERS. 1965. The BOYD, H. 1961. The flightless period of the wood duck in Massachusetts. Massachu mallard in England. Wildfowl Trust setts Div. Fish Game P-R Rep., Proj. Annu. Rep. 12:140-143. W-19-R.96pp. BRODY, S. 1945. Bioenergetics and growth. HART, J. S., AND M. BERGER. 1972. Ener Reinhold, New York. 1023pp. getics, water economy and temperature CALDER, W. A., III. 1974. Consequences of regulation during flight. Proc. Intern. body size for avian energetics. Pages 86 Ornithol. Congr. 15:189-199. 151 in R. A. Paynter, Jr., ed. Avian ener HILL, R. W. 1972. Determination of oxygen getics. Nuttall Ornithol. Club Publ. 15. consumption by use of the paramagnetic COOPER, J. A., AND M. A. JOHNSON. 1977. oxygen analyzer. J. Appl. Physiol. 33(2): Wintering waterfowl in the Twin Cities. 261-263. Loon 49(3):121-138. HOCHBAUM, H. A. 1944. The canvasback on COULTER, M. W., AND W. R. MILLER. 1968. a prairie marsh. American Wildlife Nesting biology of black ducks and mal Institute, Washington, D.C. 201pp. lards in northern New England. Vermont __ . 1955. Travels and traditions of water Fish Game Dept. Bull. 68-2. 74pp. fowl. University of Minnesota Press, DAVIS, E. A., JR. 1955. Seasonal changes in Minneapolis. 301pp. the energy balance of the English spar HOLM, E. R., AND M. L. SCOTT. 1954. row. Auk 72(4):385-411. Studies on the nutrition of wild water DOLNIK, V. R. 1971. The extent of productive fowl. New York Fish Game J. 1(2):171 energy in birds in different phases of the 187. annual cycle. E. Kologiya 2(5):89-91. (In KENDEIGH, S. C. 1949. Effect of tempera Russian.) ture and season on the energy resources I<'OLK, C., K. HUDEC, AND J. TOUFAR. of the English sparrow. Auk 66(1):113 1966. The weight of the mallard AnuB 127. platyrhynchos and its changes in the ___ . 1969. Energy responses of birds to course of the year. Zool. Listy 15(3):249 their thermal environments. Wilson Bull. 260. 81(4):441-449. FOSTER, J. A. 1976. Nutritional requirements __ , V. R. DOL'NIK, AND V. M. GAVRI of captive breeding mallards. Ph.D. LOV. 1977. Avian energetics. Pages 127 Thesis. University of Guelph, Guelph, 204 in J. Pinowski and S. C. Kendeigh, Ontario. 93pp. eds. Granivorous birds in ecosystems. FREEMAN, B. M. 1971. Body temperature Cambridge University Press, New York. and thermoregulation. Pages 1115-1151 KILGORE, D. L., AND K. SCHMIDT-NIEL in D. J. Bell and B. M. Freeman, eds. SEN. 1975. Heat joss from duck's feet 115 BIOENERGETICS OF POSTBREEDING DABBLING DUCKS immersed in cold water. Condor 77(4): PUROL, D. A. 1975. Metabolizable energy of 475-517. cellulose, three natural foods and three KING, J. R. 1972. Energetics of reproduction diets for mallards. M. S. Thesis. Michigan in birds. Pages 78-120in D. S. Farner, ed. State Univ., East Lansing. 39pp. Breeding biology of birds. National RAITASUO, K. 1964. Social behavior of the Academy of Sciences, Washington, D.C. mallard, A nas platyrhynchos, in the __ . 1974. Seasonal allocation of time and courses of the annual cycle. Pap. Game energy resources in birds. Pages 4-70 in Res. 24. 72pp. R. A. Paynter, Jr., ed. Avian energetics. RAVELING, D. G., AND E. A. LEFEBVRE. Nuttall Ornithol. Club Publ. 15. 1967. Energy metabolism and theoretical __ , AND D. S. FARNER. 1961. Energy flight range of birds. Bird-Banding 38(1): metabolism, thermoregulation and body 97-113. temperature. Pages 215-280 in A. J. Mar REED, 1. W. 1971. Use of western Lake Erie shall, ed. Biology and comparative phy by migratory and wintering waterfowl. siology of birds. Vol. II. Academic Press, M.S. Thesis. Michigan State Univ., East New York. Lansing. 71pp. LEBRET, T. 1961. The pair formation in the RICKLEFS, R. E. 1974. Energetics of repro annual cycle of the mallard, Anas platy duction in birds. Pages 151-292 in R. A. rhynchos L. Ardea 49(3):98-.158. Paynter, Jr., ed. Avian energetics. Nuttall MOILANEN, P. 1971. Etala-Hameesa Luon Ornithol. Club Publ. 15. nonvaraisesti Talvehtivista Sinisorsista. SALOMONSEN, F. 1968. The moult migra Suomen Riista 23:23-38. tion. Wildfowl Trust Annu. Rep. 19:5-24. MUNRO, J. A. 1943. Studies of waterfowl in SCOTT, M. L., M. C. NESHEIM, AND R. J. British Columbia. Can. J. Res. 21 (Sec D): YOUNG. 1969. Nutrition of the chicken. 223-260. M. L. Scott and Associates, Ithaca, NY. ORING, L. W. 1964. Behavior and ecology of 511pp. certain ducks during the post breeding SMITH, K. G., AND H. H. PRINCE. 1973. The period. J. Wildl. Manage. 28(2):223-233. fasting metabolism of subadult mallards OWEN, M., AND W. A. COOK. 1977. Varia acclimatized to low ambient tempera tions in body weight, wing length and tures. Condor 75(3):330-335. condition of mallard Anas platyrhynchos SOWLS, 1. K. 1955. Prairie ducks. The Stack platyrhynchos and their relationship to pole Co., Harrisburg, PA. 193pp. environmental changes. J. Zool. 183(3): SUGDEN, L. G. 1971. Metabolizable energy 337-395. of small grains for mallards. J. Wildl. OWEN, R. B., JR. 1970. The bioenergetics of Manage. 35(4):781-785. captive blue-winged teal under controlled ___ , W. J. THURLOW, R. D. HARRIS. and outdoor conditions. Condor 72(1):153 AND K. VERMEER. 1974. Investigations 163. of mallards overwintering at Calgary, __ , AND K. J. REINECKE. 1979. Bio Alberta. Can. Field-Nat. 88(3):303-311. energetics of breeding dabbling ducks Pages 71-94 in T. A. Bookhout, ed. Water TUCKER, V. A. 1970. Energetic cost of loco fowl and wetlands - an integrated review. motion in animals. Compo Biochem. Phy Proc. 1977 Symp., Madison, WI, N. Cent. siol. 34(4):841-846. Sect., The Wildlife Society. __ . 1973. Bird metabolism during flight: PRANGE, H. D., AND K. SCHMIDT-NIEL evaluation of a theory. J. Exp. BioI. 58(3): SEN. 1970. The metabolic cost of swim 689-709. ming in ducks. J. Exp. BioI. 53(3):763-777. WELLER, M. W. 1976. Molts and plumages of PULLIAINEN, E. 1963. On the history, waterfowl. Pages 34-38 in F. C. Bellrose, ecology and ethology of the mallards Ducks, geese and swans of North America. (Anas platyrhynchos 1.) overwintering in Stackpole Books, Harrisburg, PA. Finland. Ornis Fennica 40(2):45-66. WEST, G. C. 1968. Bioenergetics of captive ns WATERFOWL AND WETLANDS SYMPOSIUM willow ptarmigan under natural condi metabolism relationships in the black tions. Ecology 49(6):1035-1045. duck (A na.~ ru bripes.). Compo Biochem. WETMORE, A. 1921. Wild ducks and duck Physiol. 57(3AI:363-367. foods of the Bear River Marshes, Utah. WINNER, R. W. 1959. Field-feeding periodi USDA Agric, Bull. 936. 20pp. city of black and mallard ducks. J. Wildl. Manage. 23(2):197-202. WOOLEY, J. B., JR., AND R. B. OWEN, JR. 1977. Metabolic rates and heart rate- 117 WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Symp., Madison, WI, NC Sect., The Wildlife Society. T. A. Bookhout, ed. Published in 1979 HABITAT UTILIZATION BY POSTBREEDING WATERFOWL! LEIGH H. FREDRICKSON AND RONALD D. DROBNEy 2 School of Forestry, Fisheries, and Wildlife, University of Missouri-Columbia. Gaylord Memorial Laboratory, Puxico, Missouri 63960. Abstract: Studies of postbreeding waterfowl are needed to elucidate the biology and habitat requirements between breeding seasons. Movements of waterfowl immediately after breeding and habitat characteristics that attract molting waterfowl are poorly understood. Although extensive information is available on factors that stimulate and control migration, information on the nutritional and energy requirements of molting, migrating, and wintering waterfowl is minimal. Nutrition is an important factor in survival, but behavioral and habitat aspects must be understood before the constraints on survival are known. As the loss and deterioration of natural wetland habitats continue, the need to understand the factors that control survival and especially non-hunting mortality becomes increasingly important, because they provide criteria for assigning management priorities. In North America the major thrust of grounds. The assumption that studies of waterfowl research by conservation nonbreeding waterfowl have been ne agencies and by universities has been to glected is supported by the papers in elucidate breeding biology. However, the cluded in a recent bibliography on water management of waterfowl probably is fowl prepared by Reinecke, (personal more intense and extensive on stopover communication) that includes articles and wintering areas than on the breeding from 120 periodicals. Of 174 articles, 116 1 Contribution from Gaylord Memorial Laboratory (School of Forestry, Fisheries, and Wildlife, University of Missouri-Columbia and Missouri Department of Conservation cooperating), Ed ward K. Love Fellowship, and Missouri Agricultural Experiment Station, Project 170, Journal SeriesNumber8041. 2 Present address: School of Natural Resources, The University of Michigan, Ann Arbor, MI 48109. 119 HABITAT UTILIZATION BY POST BREEDING WATERFUWL were related to breeding and 58 to non creases carrying capacities for ducks. breeding. Only 3 of the 58 articles dealt Divers and dabblers that have the specifically with postbreeding activities. greatest flexibility in food habits are the Other articles on nonbreeding included most abundant species. Females of both 35 on migration, 8 on molt, 10 on winter groups switch to a higher trophic level ecology, and 2 on depredations. and consume animal foods that are Research on postbreeding has been important during pre-laying and laying. more extensive in Europe than in North Young rely heavily on invertebrate foods America. Undoubtedly, the inaccessibil for a few weeks after the hatch as well ity of many breeding areas and the close (Bartonek and Hickey 1969, Krapu 1974a, proximity to molt and wintering sites b). used by European species make post As young mature and as females com breeding studies more attractive for plete breeding, they switch to a lower Europeans than for North Americans. trophic level and feed predominantly on The paucity of information on post plant matter. Because males do not breeding emphasizes the need for more switch to high protein diets during breed research to better understand waterfowl ing, they do not show the dramatic shift biology during the 8 or 9 months when from one trophic level to another (Krapu birds are not on breeding areas. Investi 1974b). gation of postbreeding problems are par Although waterfowl are predomi ticularly difficult because waterfowl are nantly a freshwater group, a few species mobile; waterfowl that congregate on one have made the transition to marine habi site may move hundreds of kilometers tats. The best examples of anatids within 1 day, and some movements may adapted to marine environments include take waterfowl to inaccessible areas. In kelp geese (Choephaga hybrida), herbi addition, habitats used and secretive vores that live almost exclusively on behavior during molt often make study marine algae but both adults and young difficult. Biological studies can be seek fresh water for drinking (Pettingill further complicated by hunting seasons 1965); North American brant (Branta that restrict research activities on public berniela) that switch to terrestrial foods hunting areas and that may disrupt nor and concentrate near the mouths of mal patterns of waterfowl behavior. northern rivers during breeding; and A shift in strategies between breeding common eiders (Somateria mollissima), and nonbreeding waterfowl has been carnivores that use strictly marine foods described by Weller (1975). In North during brood rearing. Because cold seas America the strategies of many species are known for their richness (Ashmole change during the annual cycle because 1971), the abundance of coastal benthos of the instability of wetland ecosystems may explain why eiders are abundant at high latitudes. Freezing and the con species within their habitat range. current lack of food necessitate seasonal There is a definite tendency for water migrations to warmer latitudes. An ob fowl to shift from unstable freshwater vious question of great interest is how habitats during breeding to more stable does the smaller wintering area support and permanent wetlands or marine the waterfowl from the vastly larger situations in winter (Fig. 1). A large breeding area? Possible explanations proportion of the dabblers and divers suggested by Weller (1975) include: be that nest in the prairie pothole region of havioral changes (spacing), a shift in North America winter near the coast in habitats from freshwater to marine, and Texas and Louisiana. During winter, a shift to a lower trophic level that in seed availability is greatest in these 120 WATERFOWL AND WETLANDS SYMPOSIUM HABITAT SHIFT TROPHIC TERRESTRIAL FRESH WATER MARINE 1 NICHE SHIFT ~ CARNIVORE (C~) ------::..... lD ~ ...J ~ Fig. 1. Food and habitat shifts in migratory waterfowl of North America. southern wetlands (Arner et al. 1974, cause of a lack of information on post Knauer 1977), and agricultural prod uc breeding ecology both within and be tion makes field feeding possible (Bos tween species, the categories are tenta senmaier and Marshall 1958). Waterfowl tive. Well defined categories may never are opportunists and use these abundant be possible because several of these foods when habitat conditions permit. activities may occur concurrently. We believe that techniques developed Despite the possibility for overlap. an in recent years for breeding studies can understanding of habitat and nutritional be useful in elucidating postbreeding requirements during these periods is problems. Our intent is to review some of essential for developing a proper perspec the postbreeding studies and to attempt tive for management. We will discuss to stimulate researchers to investigate migration first and attempt to point out the challenging problems associated with the types of constraints that energy de postbreeding ecology. mands may pose for postbreeding water fowl. We have divided postbreeding activi ties into four categories on the basis of MIGRATION probable differences in nutritional and Migration has probably been studied in habitat requirements: 1) migration, more detail and is better understood than including both fall and spring move any other nonbreeding activity. Lincoln's ments and staging; 2) postbreeding dis (1935) suggestion that waterfowl used persal; 3) molt, including the complete four major flyways stimulated addi pre basic molt when birds are flightless tional research. Hochbaum (1955) re and the pre-alternate molt; and 4) win viewed early concepts of orientation and tering, including intermediate stops. Be- migratory movements with special 121 HABITAT UTILIZATION BY POSTBREEDING WATERFOWL reference to waterfowl. His extensive fore moving south; 4) reduced food avail experience with waterfowl suggested ability on preceding stopover areas may that general migratory movements are increase the number of days spent on an instinctive, but learned traditions deter area; 5) low temperatures may increase mine use of specific geographical sites. existence energy requirements and re By using data from banding, aerial duce the amount of productive energy for inventories, radar surveillance, and fat synthesis; 6) heavy hunting pressure visual sightings, Bellrose (1976) de or other harassment could also increase scribed the geographical pathways or existence energy requirements and re migration corridors and the numbers of duce feeding time. Even if the effects of waterfowl that move along each corridor the preceding variables could be estab from nesting to wintering areas. lished, efforts to estimate food require- ~ Many key findings on orientation, ments would be hampered by our lack of navigation, and movements have re knowledge of the nutritional require sulted from waterfowl studies. A ments of migratory waterfowl. description of pre migratory behavior In the previous paper, Prince described indicates that on the day of migration the general relationships between tem blue-winged teals (Anus discors) shifted perature and energy (See Fig. 3, p. 107). feeding times to midday (Owen 1968). Although this figure is not completely Other behavioral changes included in accurate with respect to waterfowl creased wing flapping, turning into the under free-living conditions, the relation wind, swimming south, less calling, more ships between temperature and energy comfort movements, and especially alert do provide a generalized framework for' postures prior to departure. Migration discussing energy requirements. At the movements are not normally initiated outset, it is important to point out that under cloud cover, beacause either the the existence energy values are normally sun or stars are necessary for orientation derived from birds confined to small (Hamilton 1962, Bellrose 1966, 1971). cages so that activity is restricted. There Landmarks and wind provide additional fore, there is a curve of unknown form cues for navigation once movements are that represents the energy requirement underway (Bellrose 1966, 1971). Emlen of "free existence." For most tempera (1975) provided a comprehensive review tures, this curve probably lies above the of migration by waterfowl and other existence energy curve. This added birds. energy requirement for free existence Despite the extensive work on migra would reduce the amount of energy avail tion, an important problem facing able for productive processes. An esti managers is how to estimate the food mate of the energy requirements for free requirements of migratory waterfowl. existence could be made by applying the This problem is complicated by a number costs of various activities to time budget of variables: 1) the number of waterfowl data. Unfortunately, this kind of infor using an area changes from year to year; mation is not available for waterfowl 2) waterfowl use days can be affected by during migration. local temperature, water conditions, and Although ingested (potential) energy is food availability; 3) energy requirements represented as a constant, the actual at stopover areas may vary with the con amount of energy available is probably dition of birds leaving breeding or molt also variable under free-living condi ing areas, and if breeding is delayed, tions. The amount of energy that a bird hens and young may not have had assimilates can be affected by the physi enough time to store migratory fat be cal and chemical properties of the foods 122 WATERFOWL AND WETLANDS SYMPOSIUM Table 1. Estimated energy costs and time to replenish endogenousfat reserves for migra tory waterfowl weighing1100 g. Days to replenish fatC Flight Distance a Kcalb 480Kcal 390Kcal time (h) (km) used intake intake 2 128 120 0.8(0.6) 1.7(1.0) 4 256 240 1.5(1.1) 3.5(2.0) 6 384 360 2.3(1.7) 5.2(3.0) 8 512 480 3.0(2.3) 6.9(3.9) 10 640 600 3.8(2.8) 8.6(4.9) 12 768 720 4.5(3.4) 10.3(5.9) 14 895 840 5.3(4.0) 12.1(6.9) a Flight time X a flight speedof 64km/h (Tucker 1971'). b Caloriccost offlight/h =55.7 W 0.78 (Tucker1970, 1973, from King 1974). C Based on an estimated existence energy requirement of 3.4X BMR and potential energy values of 480·and 390 kcal/day. Open figures derived using BMR estimates for mallards; BMR :::87.9WO.734(Prince, personal communication). Figures in parentheses derived using estimates for nonpasserinesat rest; BMR=73.5 WOo 734(Aschoffand PohI1970). eaten, food availability, and feeding mained the same, suggesting that they behavior. were relying partially on fat reserves Hard seeded food items may be re (Owen 1970). These results indicate that tained in the gizzard for several days free-living birds may attempt to "wait and/or they may pass through the diges out" cold snaps, seeking additional food tive tract intact (Swanson and Bartonek only when body reserves reach a certain 1970). The passage rate of some foods low level. therefore may limit the rate at which There is some evidence that waterfowl energy can be assimilated. Foods that replenish metabolic reserves utilized pass through the digestive tract intact during migration at stopover areas prior are of no nutritive value to the bird and to proceeding on the next leg of their reduce foraging efficiency (energy de journey (Harris, personal communica rived per unit of energy expended in tion). If adequate data were available, it foraging). would be possible to estimate the time Potential energy differs according to and energy needed to replenish reserves the chemical composition of each food at various points along the migratory because the metabolizable energy (ME) route. content is variable. The effect of ME on The kind of information needed to potential energy would probably be most make these calculations is not available, pronounced when food supplies become but to serve as an illustrative case, we depleted and the foods being consumed have made some very broad assumptions are low in ME. concerning energy requirements and cal In addition to its effect on existence culated the number of days needed to energy, temperature may change poten replenish fat reserves for migratory tial energy through its influence on for flights 2 to 14 h in duration (Table 1). aging behavior. After a sudden decrease These estimates were computed for a in temperature, food intake by captive mallard (Arms platyrhynchos) weighing blue-winged teals often decreased or re 1.1 kg with BMR of 87.9 WO.734 (Prince, 123 HABITAT UTILIZATION BY POSTBREEDING WATERFOWL personal communication), an energy 245.86 kcal per bird. This quantity is requirement for flight of approximately sufficient to account for only 77 percent 55.7 WO.78 (Tucker 1970, 1973, from of our estimated cost of free existence King 1974), a flight speed of 64 km/h (320.62 kcal). Even if the 245.86 kcal of (Tucker 1971), and an existence energy energy were sufficient to meet free exis requirement of 3.4 X BMR. Maximum tence requirements, this amount would potential energy (480 kcal/day) was not be adequate to meet the needs for based on food consumption by penned productive processes such as replenish mallard hens during egg laying (Prince, ment of fat reserves. personal communication). Reduced cal Twenty years ago, when wetland oric intake can have a dramatic effect on habitats were more abundant, genera the time needed to replenish fat reserves. lized estimates of food requirements To demonstrate this point, we have re might have been adequate. However, the duced the daily caloric intake by 19% currently increasing impact of a man (390 kcal/day). This reduction more than altered environment predicates a need to doubles the estimated time required for better understand and provide for the fat replenishment. It should be pointed nu tritional requirements of migratory out that these estimates represent a sim waterfowl. Some possible factors that plified case and that actual requirements may influence the energy budgets of may be greater or less that the figures present day migrants are outlined in listed. Our intent in presenting these Fig. 2. data is not to define precisely the re The decline in natural wetlands along quirements for migration, but to em phasize that a new approach is needed to allow a more realistic assessment of the WETLANDS DECREASE food requirements of migratory water 1 fowl and that this approach requires WATERFOWL CONCENTRATIONS INCREASE more information than is currently avail able. / -, Past estimates based on waterfowl-use RAPID FOOD DEPLETION HUNTING PRESSURE I \ l days and food consumption of penned FORAGING TIME LONGER HARASSMENT AND waterfowl probably are lower than INCREASES FORAGING MOVEMENTS INCREASE actual food requirements. Free-living FLIGHTS waterfowl almost certainly incur a greater energy cost as a result of forag ing and daily feeding flights than do penned birds under ad libitum food con ENERGY FOR FAT DEPOSITION DECREASES ditions. Energy required for the replen TIME REQUIRED FOR REPLENISHMENT ishment of metabolic reserves by INCREASES migrants must also be established. 1 TIME ON STOPOVER AREAS INCREASES To illustrate the point, we have taken AMBIENT TEMPERATURE DECREASES our admittedly tenuous estimates and compared them with estimates based on the average intake of corn (71.68 g/bird/ 1 day) by mallards during December in PRODUCTIVE ENERGY DECREASES lllinois (Jordan 1953). If the ME value of corn (3.43 kcal/g) reported for poultry Fig. 2. Potential effects of decreasing wetlands (Scott et al. 1969:452) is used, the daily and increased waterfowl concentrations on the intake of metabolizable energy would be energy budgets of migrant waterfowl. 124 WATERFOWL AKD WETLANDS SYMPOSIUM migration corridors has resulted in a (1968) distinguished several situations greater concentration of waterfowl on in which the molting occurs: 1) on or many stopover areas. Concentrating immediately adjacent to the breeding waterfowl creates two problems that areas; 2) during the fall or spring migra could adversely affect their energy bud tion; 3) on the wintering grounds; and 4) gets. First, food supplies become de on a special area distinct from the breed pleted more rapidly. Decreased food ing grounds. Typically adults and parti availability necessitates increased forag cularly males and broodless females ing time and/or longer foraging flights move to molting areas after breeding, for those species that field feed. Second but immatures move directly to these ly, hunting pressure tends to increase in areas from the wintering sites or from areas where waterfowl are concentrated. the stopover points used during spring' Harassment by hunters could cause in movements. He further classified the creased movements and reduce time molting areas on the basis of flock available for foraging. Both problems characteristics: 1) individuals or small ultimately result in a reduction in the groups; 2) small flocks of usually no more amount of productive energy available than a few hundred birds, but occasional for fat deposition and thereby increase ly up to a thousand birds; and 3) huge the time needed for replenishment. As congregations that may number hun the duration of stay increases, the effect dreds of thousands of birds. of declining ambient temperature could The initiation of postbreeding activi compound energy problems by increas ties is variable and depends on the sex, ing existence energy requirements. It species, and chronology of nesting. The would seem theoretically possible that a chronology of dispersal from breeding combination of these factors could create areas is an important constraint on post a situation whereby migrants with de breeding strategies. Those species that pleted fat reserves would be unable to leave the breeding grounds late in the replenish their reserves and, therefore, annual cycle must molt, regain flight, could not continue migration. and accumulate sufficient energy re serves for migration prior to freeze-up. POSTBREEDING DISPERSAL In species that pair annually, most Many waterfowl have developed molt males leave the breeding areas before migrations that are described as mass females with or without broods. Some movements to traditional areas where mallard and wood duck (Aix sponsa) the pre-basic molt occurs. The molting drakes may depart during laying, but areas provide food, cover, and isolation most leave during early incubation and when the birds are flightless and vulner a few remain with their hens until hatch able to predation. This movement of ing (Gilmer et al. 1977). In the Chippewa males and non breeders may be an adap Forest of Minnesota, all male mallards tation to reduce competition for food on left the breeding area to molt, but 48% of breeding areas (Salomonsen 19(8). Post the male wood ducks molted on the breeding dispersal is distinct from the breeding area (Gilmer et al. 1977). Most fall migration because the direction of drake pintails (Anas acuta), redheads flight is often opposite from that of fall (Aythya americana), canvasbacks (A. movements, breeding females generally valisineria), and lesser scaups (A. aJJinis) do not participate in the movements, and leave in early incubation, whereas the birds usually congregate on specific most wigeons (Anas americana), shov geographical areas in large concentra elers (A. clypeataj, and gad walls (A. tions (Salomonsen 1968). Salomonsen strepera) leave in mid-incubation. Blue 125 HABITAT UTILIZATION BY POSTBREEDING WATERFOWL winged and cinnamon teals (A. cyanop scaups (Aythya manla), and oldsquaws tera) and ruddy ducks (Oxyura jamai (Clangula hyemalis) are most common, censis) generally leave the breeding areas with nearly 300,000 of each species pres in late incubation (Oring 1964, Bellrose ent. Goldeneyes (Bucephala sp.), buffle 1976). Ruddy ducks may go through the heads (Bucephala albeola ), and canvas flightless period on the wintering backs occur in lesser numbers and gen grounds (Palmer 1976:505). Delayed molt erally total less than 25,000. On the might be in part an adaptation related to Camas National Wildlife Refuge in late nesting by some birds and late Idaho, 52,000 molting dabbling ducks that departure from the breeding grounds included 25,000 mallards, 20,000 pintails, (Bellrose 1976). 5,000 wigeons, and 2,000 teals of 3 species Some broodleis wood duck and mal used 4,265 ha of wetlands (Oring 1964). lard females leave the breeding area as In Europe molting mute swans (Cyg early as some of the drakes, but most of nus olor) congregate on traditional these nonbreeding females remain molting areas that have been used for at several weeks longer than males (Gilmer least 350 years (Mathiasson 1973a, b). et al. 1977). Brood females delay their Some swans appear on the molting areas departure from breeding areas until as early as mid-May and most have de broods are reared, but the time of depar parted by mid-November. Flightless ture varies with each species. swans can be found from mid-June to Female redheads and white-winged mid-October, but individual birds are scoters (Melanitta fusca) consistently flightless for about 1 month. leave their broods before the young reach Despite a lack of supporting evidence flight stage (Weller 1959, Brown 1977). to elucidate evolutionary development of molt migrations, these movements ap MOLT AND POSTBREEDING pear to maximize individual fitness. CONGREGATIONS Theoretically food is one important fac tor in the development of molt migra Waterfowl concentrations on molting tions (Salomonsen 1968). When im areas may include aggregations of sever matures, males, and broodless females al species in varying num bers. On Swan move from the breeding areas, the com Lake (310 krn-) in southwestern Mani petition for foods required for brood toba, male pochards were predominant rearing is reduced. There is a tendency and accounted for 85 to 95% of the molt for waterfowl to shift to molting sites ing population (Bergman 1973). In July where breeding is limited (Salomonsen and August 11,000 dabblers, including 1968). Some high latitude molting areas 5,000 wigeons, used the area. As many as that are exploited by nonbreeding or 3,000 canvasbacks and 20,000 redheads postbreeding waterfowl are unsuitable used the lake in early September, but the for breeding waterfowl because they are 2 species segregated themselves. During ice-free only for short periods. Ducks staging an estimated 50,000 American that breed in more southern ecosystems coots (Fulica americana) also used the may also use tundra wetlands for molt area in September and lesser scaups ing. For example, cavity nesting species occurred in large concentrations in such as goldeneyes and buffleheads October. have moved from boreal forest breeding In Alaska, Takslesluk Lake, a 67,340 areas to the tundra for molt (King 1973). km2molting area on the Yukon Delta, Although large concentrations of birds may hold nearly a million ducks of sever may use a given molting area, competi al species (King 1973). Pintails, greater tion for food could be reduced by inter 126 WATERFOWL AND WETLANDS SYMPOSIUM specific differences in foods eaten, feed molting waterfowl were found on lakes ing habitat, and feeding behavior. On where considerable human activity oc Swan Lake in Manitoba, canvasbacks curred in summer (Bergman 1973). Not concentrated near beds of Potamogeton only do waterfowl seek out secluded pectinatus and P. richardsonii, but red areas for molting, but their behavior is heads used a different part of the lake also secretive (Oring 1964, Owen 1970). where Scirpus acutus occurred as scat tered clumps and P. pectinatus, Ruppia occidentalis, and Chara sp. predominated WINTERING (Bergman 1973). Stopover and staging areas may serve Molting swans in the Baltic area as extensions of the wintering areas. This appear to be attracted to sites with ex is particularly true when abundant food tensive submergent vegetation. Mute supplies hold large populations at north swans preferred sites where Zostera ern latitudes during mild weather. The marina and Ulva lactuca were abundant use of food resources at higher latitudes (Mathiasson 1973a). Estimates of food reduces the demand for food on winter resources required for the equivalent of ing habitats and may enable birds to 94,561 swans for the 5-month period arrive on the wintering areas in better from 22 May to 25 October was 401,523 condition. kg of Zostera and 22,832 kg of Ulva or a Recent work on wintering and stopover total of 424,355 kg of fresh plant materi areas indicates that waterfowl have al. There is some evidence that when the specific habitat requirements for feeding carrying capacity of a traditional molting that allow a variety of ducks to exploit site is reached, molting concentrations food resources. In March and April in develop elsewhere. For example, a molt southeastern Missouri, shovelers consis ing population in one Baltic area has re tently used water between 17 and 23 cm mained rather constant, but the breeding deep (Taylor 1977) on areas with produc population has tripled (Mathiasson tion of natural foods like millet ( Echi 1973b). nochloa crusgalli) or smartweeds (Poly Our ability to estimate energy and gonum sp.). Pintails used slightly shal nutrient requirements for molt is severe lower water (14 to 21 em) and mallards ly limited by the lack of data on the tim consistently used the shallowest water ing and duration of molt for free-living (11 to 16 cm). These findings suggest that waterfowl. Time budget information is when fields with natural vegetation are essential to assign the costs of daily flooded too deeply, conditions are unsuit energy demands, but such data are diffi able for feeding by most dabbling ducks. cult to obtain because of the secretive The goal of management on many pub habits of molting ducks. licly owned areas is to provide hunting There is some evidence that molt may opportunities. When habitat conditions influence premigratory physiology and such as water depth are unsatisfactory behavior. Owen's (1970) work with blue to attract ducks, not only are food re winged teals suggests that there may be sources unavailable, but hunting op an inhibitory effect of molt on prevernal portunities are reduced. fat deposition and nocturnal activity. A more sophisticated approach (princi Waterfowl require isolation on molting pal component analyses) to determine areas (Salomonsen 1968). The use of iso wintering requirements of 13 species of lated high latitude lakes suggests that waterfowl in Texas from 3 October to 15 birds seek seclusion during the flightless December indicated that waterfowl period. In southwestern Manitoba few exploited several habitat niches on win 127 HABITAT UTILIZATION BY POSTBREEDING WATERFOWL tering areas (White and James 1978). influence daily activity patterns. Interestingly, the mottled duck (A nas fulvigula) restricted its use to the shal SUGGESTED APPROACH TO lowest water and was segregated from POSTBREEDING STUDIES all other species. Of the species studied, only mottled ducks bred in the area. The The study of postbreeding ecology mottled demonstrated habitat pref should provide an understanding of habi erences different from all other species tat use and resource allocation in relation even though the investigation was con to the requirements of the organism. The ducted during the time of nonbreeding. habitat must therefore be evaluated both The other ducks were classified into in terms of its physical characteristics three groups that exploited water of in and how its use relates to the behavioral, creasing depths as follows: 1) bl ue physiological, and psychological needs of winged and green-winged teals (A. crecca the organism. Our proposed approach is carolinensis) and shovelers; 2) fulvous a comprehensive one requiring the inte whistling ducks (Dendrocygna bicolor), gration of a number of elements (Table pintails, gad walls, wigeons, and ring 2). Even though waterfowl exploit dif necked ducks (Aythya collaris); and 3) ferent habitats and have requirements ruddy ducks, redheads, canvasbacks. and after breeding that are different from lesser scaups. those during breeding, the same basic In the Lou isiana coastal marshes questions must be answered. green-winged teals and pintails form Ultimately research efforts should large diurnal concentrations on resting provide answers to three basic questions: areas that have large open expanses and 1) How do postbreeding waterfowl appor slightly sloping beaches so that whatever tion their time and energy; 2) What are the water level, a broad strip of shallow the characteristics of the habitat used; water is available (Tamisier 1976). The and 3) Why is time apportioned among three primary daily diurnal activities activities and habitats as it is? Because were: sleeping (8 to 9 h), preening (2 to the essential continuity between the 3 h and related to molt), and swimming. organism and the environment is re Feeding was an insignificant diurnal vealed most obviously in energy ex activity. Ducks consistently fed at night, changes and transformations (King 1974: and both the timing and direction of 4), time and energy budget data provide flights were constant. Hunting did not a central framework for evaluating and Table 2. Suggested areas of research emphasis for the study of postbreeding waterfowl. Habitat Foods Behavior Physiology Wetlands used Foods consumed Time budget Condition Vegetation Feeding associations habitat Feeding Hormones Chemical Inter- and intra and physical Chemical specific characteristics composition interactions Nutrition Man's developmental Meteorological Nutritional and recreational data values activities Metabolizable energy 128 WATERFOWL AND WETLANDS SYMPOSIUM integrating data on, e.g., habitat selec FOOD AND tion, food habits, and changes in con NUTRITION dition. On the basis of energetics work during ~HYSIOLOGY the breeding season, we suggest that -: HABITAT AND productive work include the following ~ /CONDITION components: food and nutrition, habitat, physiology and condition, weather, com TIME petition, behavior, and time and energy AND budgets (Fig. 3). Although a comprehen sive discussion of the potential inter actions among these components is inap /''''''~ propriate here, we will suggest several WEATHER COMPETITION approaches that have been successful in our studies. Preliminary time budget studies are useful in identifying habitats ~/ used and suggest sites where data on BEHAVIOR habitat characteristics and food habits should be collected. Once foods are iden Fig. 3. Use of time and energy budget data for tified, their nutritional values (e.g., the integration of major elements in the study chemical composition and ME) should be of postbreeding waterfowl. determined. Carcasses of birds collected can be used to establish baseline data on Obviously, these are complex problems body and organ weights and measure that are best solved by teams of re ments and on carcass composition. These searchers or in programs with several data are important in determining students working simultaneously. The changes in condition and how the use of opportunity to better understand post metabolic reserves relates to strategies breeding ecology is an exciting challenge employed at various stages in the annual with a broad range of research oppor cycle. tunities and management applications. 129 HABITAT UTILIZATION BY POSTBREEDING WATERFOWL LITERATURE CITED ARNER, D. H., E. D. NORWOOD, AND B. M. ducks in north-central Minnesota. J. TEELS. 1974. Comparison of aquatic WildI. Manage. 41(3):345-359. ecosystems in two national waterfowl HAMILTON, W. J., III. 1962. Celestial orien refuges. Proc. Southeastern Assoc. Game tation in juvenal waterfowl. Condor 64(1): and Fish Commissioners 28:456-467. 19-33. ASCHOFF, J., AND H. POHL. 1970. Der HOCHBAUM, H. A. 1955. Travels and tradi Rueheumasatz von Vogeln als Funktion tions of waterfowl. Charles T. Branford der Tageszeit und der Korpergrosse. J. Co., Newton, MA. 301pp. Ornithol. 111(1):38-47. JORDAN, J. S. 1953. Consumption of cereal ASHMOLE, N. 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Feeding ecology of pin __ . 1971. The distribution of nocturnal tail hens during reproduction. Auk 91(2): migrants in the air space. Auk 88(2): 278-290. 397-424. __ . 1974b. Foods of breeding pintails in __ . 1976. Ducks, geese, and swans of North Dakota. J. Wildl. Manage. 38(3): North America. Stackpole Books, Harris 408-417. burg, PA, and Wildlife Management Institute, Washington, D.C. 544pp. LINCOLN, F. C. 1935.The waterfowl flyways of North America. U.S. Dept. Agric. Circ. BERGMAN, R. D. 1973. Use of southern 342. 12pp. boreal lakes by postbreeding canvasbacks and redheads. J. WildI. Manage. 37(2): MATHIASSON, S. 1973a. Moulting grounds 160-170. of mute swans (Cygnus alar) in Sweden, their origin and relation to the population BOSSENMAIER, E. F., AND W. H. MAR dynamics of mute swans in the Baltic SHALL. 1958. Field-feeding by waterfowl area. Viltrevy 8(6): 400-452. in southeastern Manitoba. Wildl. Monogr. 1.32pp. __ . 1973b. A moulting population of non BROWN, P. W. 1977. Breeding biology of the breeding mute swans with special re white-winged scoter (Melanitta fusca ference to flight-feather moult, feeding deglamii). M. S. Thesis. Iowa State Univ., ecology, and habitat selection. Wildfowl Ames. 51pp. 24:43-53. EMLEN, S. T. 1975. Migration: Orientation ORING, L. W. 1964. Behavior and ecology of and navigation. Pages 129-219 in D. S. certain ducks during the postbreeding Farner and J. R. King, eds. Avian biology. . period. J. Wildl. Manage. 28(2): 223-233. Vol. 5. Academic Press, New York. OWEN, R. B., JR. 1968. Premigratory be GILMER, D. S., R. E. KIRBY, 1. J. BALL, havior and orientation in blue-winged teal AND J. H. RIECHMANN. 1977. Post (A na.~ discors). Auk 85(4):617-632. breeding activities of mallards and wood __ . 1970. The bioenergetics of captive 130 WATERFOWL AND WETLANDS SYMPOSIUM blue-winged teal under controlled and M. S. Thesis. Univ. of Missouri, Columbia. outdoor conditions. Condor 72(2): 153-163. 98pp. PALMER, R. S., ed. 1976. Handbook of North TUCKER, V. A. 1970. Energetic cost of loco American birds. Vol. 3. Yale University motion in animals. Compo Biochem. Phy Press, New Haven, CT. 560pp. siol. 34(4):841-846. PETTINGILL, O. S. 1965. Kelp geese and __ . 1973. Bird metabolism during flight: flightless steamer ducks in the Falkland evaluation of a theory. J. Exp. BioI. 58(3): Islands. Living Bird 4:65-78. 689-709. SALOMONSEN, F. 1968. The moult-migra __ , and K. Schmidt-Koenig. 1971. Flight tion. Wildfowl 19:5-24. speeds of birds in relation to energetics SCOTT, M. L., M. C. NESHEIM, AND R. J. and wind directions. Auk 88(1):97-107. YOUNG. 1969. Nutrition of the chicken. WELLER, M. W. 1959. Parasitic egg laying M. L. Scott and Associates, Ithaca, NY. in the redhead (Aythya americana) and 511pp. other North American Anatidae. Eco!. SWANSON, G. A., AND J. C. BARTONEK. Monogr. 29(4):333-365. 1970. Bias associated with food analysis __ . 1975. Migratory waterfowl: a hemi in gizzards of blue-winged teal. J. Wildl. spheric perspective. Pu blicaciones Biolo Manage. 34(4):739-746. gicas Instituto De Investigaciones Cienti TAMISlER, A. 1976. Diurnal activities of ficas, U.A.N.L. 1(7): 89-130. green-winged teal and pintail wintering in Louisiana. Wildfowl 27:19-32. WHITE, D. H., AND D. JAMES. 1978. Dif ferential use of fresh water environments TAYLOR, T. S. 1977. Avian use of moist soil by wintering waterfowl of coastal Texas. impoundments in southeastern Missouri. Wilson Bull. 90(1):99-111. 131 WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Syrnp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Pu blished in 1979 WINTER HABITAT OF DABBLING DUCKS PHYSICAL, CHEMICAL, AND BIOLOGICAL ASPECTS ROBERT H. CHABRECK School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge, Louisiana 70803 Abstroct: Each fall some 50 million dabbling ducks representing 10 species depart the northern breeding grounds and make their way southward for the wintering season. Birds begin arriving on the wintering grounds in August and remain through April the following year. Migrant dabbling ducks make use of winter habitat 8 months of the year, and, as a result, are greatly influenced by habitat quality and abundance during that time. Diversity of habitat is an impor tant aspect of meeting the requirements of the many species involved. Important features of winter habitat are presented for the various species and include physical, chemical, and biologi cal aspects. Physical features affecting winter habitat include distribution of aquatic area, water depth, and weather patterns. Important chemical aspects are soil and water salinity and habitat pollution. Major biological considerations are food availability, diseases, and parasites. The availability of suitable breeding breeding condition of birds departing habitat is the major factor affecting con from them in the spring. tinental populations of dabbling ducks in The selection of winter habitat by North America; however, the importance dabbling ducks is, like fall migration, of winter habitat should not be over primarily a matter of tradition. Areas looked. Certain species, such as bI ue visited during a wintering season are winged teals (Anas discors), begin fall usually those visited previously. How migration in August and remain on ever, continued use during a wintering wintering grounds into the following season varies with habitat quality and May, a period exceeding 8 months of the preferences of the individual species, as year. Most others use winter habitat in well as individual birds or groups within excess of 7 months. Conditions on the a species. The quality of winter habitat wintering grounds can influence the encompasses numerous physical, chemi welfare of birds using them and also the cal, and biological factors that can 133 WINTER HABITAT OF DABBLING DUCKS change within a period of only a few levels. hours to make an area less attractive or Gadwalls (A. streperai, American more attractive to ducks. Large-scaled wigeons (A. americana), and shovelers changes in habitat quality can even (A. clypeata) are commonly found on modify migratory patterns. The purpose shallow, open lakes containing dense of this paper is to' review some of the growth of aquatic plants. On their arrival factors affecting winter habitat quality to the Louisiana coast in October, gad for dabbling ducks. walls and wigeons will congregate in large bodies on isolated, brackish lakes, PHYSICAL ASPECTS often with as many as 5,000 birds on an OF WINTER HABITAT area of less than 10 ha. The birds are at tr acted there by dense wigeongr ass Species Preferences (Ruppia maritima), remain until stands are depleted, then disperse to other near Although dabbling ducks are adapted by areas. However, they remain mostly for use of shallow water areas, feeding in open water habitat, selecting whatever and resting habitats selected by the indi may be available. Gadwalls also occupy vidual species vary. In fact, certain lakes in forested bottomlands that con species have different habitat prefer tain abundant aquatic growth. Wigeons, ences in different parts of their range. however, will disperse to upland areas For example, the mallard (A. platyrhyn for feeding and frequently cause damage chos) seems equally at home in the corn to green agricultural crops (Horn 1949). fields of the Midwest as it does in the During early spring, large flocks of flooded pin oak (Quercus palustris) flats wigeons may be seen feeding out of water of Arkansas or the coastal marshes of on newly sprouted vegetation on the Louisiana. Mississippi River Delta. The shoveler, Pintails (A. o.cuta) also display con though more of an opportunistic feeder, siderable variability in habitat selection; remains in aquatic habitat. in certain regions they depend heavily on The wood duck (Aix sponsa), as its grain and soybean fields for feeding, but name implies, is typically a bird of elsewhere they may use shallow water forested areas, occupying sloughs, marshes and impoundments, even when streams, lakes, and flooded timber. agricultural crops are nearby. Mallards Exceptions to this have been noted in and pintails feed largely on seeds, and several areas; in Louisiana wood ducks select habitats with an abundance of this are occasionally seen in coastal marshes food easily available. However, at times considerable distances from timbered pintails will raft on large, shallow water areas, and Bellrose (1976) reported feed lagoons and feed almost entirely on sub ing in corn fields. merged aquatics. Mallards, on the other Cowardin (1969) studied use of flooded hand, are more secretive and in marshes timber and marsh by mallards, black or other aquatic habitats are commonly ducks (Anas rubripesi, and wigeons and found in small ponds and potholes. noted that the birds spent more time Blue-winged and green-winged teals resting than feeding in timbered areas (A. carolinensisl are the smallest of the and more time feeding than resting in dabbling ducks and appropriately select marsh areas. Mallards and black ducks habitats with shallowest waters, often used flooded timber during the fall as a feeding or resting on mud flats. They rest area at night and flew out to nearby frequently shift about on local winter agricultural fields for feeding during the habitat in response to changes in water day. The preference of flooded timber 134 WATERFOWL AND WETLANDS SYMPOSIUM over the adjacent marsh was attributed tial component of dabbling duck winter to the abundance of logs, which provided habitat, the relationship of open water almost unlimited loafing sites. to marsh or terrestrial areas often deter mines the attractiveness of a particular Distribution of Aquatic Habitat habitat. Even small wetland areas can provide important wintering habitat if The construction of permanent water open water areas are properly dispersed. areas over the past several decades has Where adequate water areas are not resulted in broad changes in the distribu available, they can be easily developed tional pattern of dabbling ducks. Reser (MacNamara 1957), and thus provide voirs constructed for irrigation, flood better distribution of birds and improve control, and hydroelectric power have opportunity for harvest. Hopper (1972) provided permanent water to regions observed that marshes without adequate where the absence of available water open water or a proper interspersion previously limited winter use by dab between water and cover are normally bling ducks (Williams 1964). In the short avoided by dabbling ducks. Efforts to history of reservoir construction in the create more open water in a dense Colo United States, 1,300 reservoirs were con rado marsh resulted in increased duck structed by 1954 with a water storage of use. 4.5 million surface hectares. By 1964, Fresh marshes in southeastern Louisi another 1 million surface hectares were ana that are overgrown with vast, un added and the predictions were for a broken stands of maidencane (Panicum total of 16 million surface hectares by the hemitomon) receive little duck use. Open year 2000 (White and Malaher 1964). ing such stands by prolonged flooding or Also, farm ponds for livestock watering temporary exposure to brackish water and fish production literally dot the land makes the area more attractive to dab scape and constitute a key segment of the bling ducks. In brackish marshes, wire winter habitat in many areas. Edminster grass (Spartina patens) presents a simi (1964) estimated that by 1980, 2.5 million lar problem, and its gradual encroach farm ponds covering 1.2 million hectares ment into marsh ponds results in re would be available to waterfowl. duced use by ducks. The creation of new aquatic habitats An excessive amount of open water can occurred at the same time that millions also present problems. Large ponds are of hectares were being lost because of more exposed to wind and wave action habitat alterations. Newly constructed and less attractive to dabbling ducks. water areas receiving greatest use were Duck use is often limited to coves in such those in close proximity to agricultural areas, which offer some protection. areas. Dabbling ducks. particularly mal lards, used the reservoirs and ponds as Water Depth rest areas and spread out to adjacent grain fields to feed (White and Malaher Water is an essential element of winter 1964). The abandonment of traditional habitat for most species of dabbling wintering areas for the new man-made ducks and must be present in proper habitat resulted in a more even distribu amounts for an area to be attractive. tion of dabbling ducks on the wintering Inadequate amounts and excessive grounds. New areas most readily used amounts both regulate food availability. were those within or near natural fly Bu rgess (1969) described methods of ways (Edminster 1964). regulating dabbling duck use of manage Although available water is an essen ment units on Squaw Creek National 135 WINTER HABITAT OF DABBLING DUCKS Wildlife Refuge in Missouri by manipu water levels than most other species of lating water levels. Units were flooded to dabbling ducks. a shallow depth in the fall to attract Wills (1965) related water depths to ducks, drawn down in December to dis dabbling duck populations on Catahoula courage winter use and move ducks from Lake in central Louisiana and reported the refuge, and flooded in spring to at tremendous concentrations of most spe tract ducks during northward migration. cies during the fall and early winter In an evaluation of duck use of marsh when depths were less than 0.5 m and impoundments in Louisiana, Chabreck favorable for feeding. Deeper flooding in et al. (1974) noted several instances late winter caused most dabblers to where waterdepth affected duck popula abandon the area. The purpose of deeper tion levels and distributional patterns. flooding was to restrict feeding in the Blue-winged teal use of impoundments lake and prevent the birds from consum was related to water depth, independent ing lead shot deposited during the hunt of foods present. The area studied nor ing season. Mallards and pintails con mally received high use by blue-winged tinued to use the lake as a rest area but teals from late August into October; moved out into nearby soybean fields to however, brackish water impoundments feed. were mostly dry in August 1970 and con tained very few teals as a result. Heavy Weather rains associated with Hurricane "Felice" in mid-September raised water levels, Weather patterns are a key factor and teal populations were much larger by regulating fall migration of dabbling the following week. The following year a ducks (Hochbaum 1955), and the behav contrasting situation was observed in the ior of birds on wintering grounds is also brackish water impoundments. Water greatly affected by weather conditions. levels and blue-winged teal populations Nelson (1954) reported that ducks remain in late August 1971 were similar to those on winter habitat in Utah until lakes and present in September 1970. Then, Hurri ponds freeze over, thus forcing most cane "Edith" struck the area in mid birds from the area. Bellrose (1976)noted September 1971, and over 12 inches of that over 1 million mallards winter in the rain fell in the study area. As a result, Midwest and feed in corn fields when water depths increased greatly and teal lakes and marshes become frozen. Many use declined drastically. birds remain until snow cover becomes Other species were also responsive to too deep for field feeding. Ducks forced changes in water depth and increased or southward by adverse weather may re decreased use of an area as water depths turn when conditions improve. changed. Green-winged teals preferred Rainfall plays a key role in renovating areas with water depths less than 10 cm winter habit (Lynch 1964). Annual plants and moved from areas whenever the provide valuable food sources in wet water depth increased. Numbers of div lands, particularly in the Deep South, ing ducks such as lesser scaups (Aythya and summer drying is necessary for affinis), ring-necked ducks (A. collaris), germination and growth (Chabreck 1959) and ruddy ducks (Oxyura jamaicensis) Dry summers usually result in abundant generally increased as water depths in growths of annuals in marshes and creased. Gadwalls, wigeons, and shov swamps; however, fall and winter rains elers, which feed heavily on aquatic are necessary to restore water and make vegetation or animal material, were nor the seeds produced available to wintering mally found under a wider range of birds. 136 WATERFOWL AND WETLANDS SYMPOSIUM Hurricanes in coastal areas may have but widened 3.4 km in the southeast. The adverse effects by sweeping away impor brackish type in southwestern marshes tant aquatic plants in tidal surges (Grif was 8.2 km wide on the earlier map but fith 1939). Impoundments and other only 4.2 km wide by 1968, a reduction of habitat development projects may also about 47 percent. In southeastern be damaged by rushing waters(Ens marshes, the brackish type was 10.6 km rninger and Nichols 1957). Hurricanes wide in 1943 but increased to 13.4 km in often improve winter habitat by revers width by 1968. ing plant succession and improving The widening of saline and brackish conditions for growth of annual plants. vegetational types in southeastern Louisiana resulted from saltwater intru CHEMICAL ASPECTS OF sion from the Gulf of Mexico into inter WINTER HABITAT mediate and fresh types and was caused by increased canal dredging and stream ....Soil and Water Salinity channelization. The reduction in width of the brackish type in southwestern In coastal areas, soil and water salinity Louisiana reflects a reduction in water is usually the major factor regulating salinities in that area that resulted from plant species composition of lakes and saltwater barriers on irrigation projects marshes (Penfound and Hathaway 1938). and special management practices on It is also one of the principal factors wildlife refuges. Because dabbling duck limiting plant growth in certain western use is greater in fresh and intermediate areas (Nelson 1954). The Louisiana vegetational types, the change represents coastal marsh has been delineated into an improvement of winter habitat in 4 vegetational types on a basis of salinity southwestern Louisiana and a deteriora (Chabreck 1972). The types occurred in tion in southeastern Louisiana (Chabreck bands generally paralleling the coastline, 1970). contained characteristic floral patterns, and were designated as saline, brackish, Habitat Pollution intermediate, and fresh. Plant species diversity and the number of duck food The wide-scale release of chemical plants increased with decreasing water pollutants into aquatic and wetl and salinity (Chabreck 1970, Martin and environments is a matter of great con Uhler 1939). Palmisano (1972) studied cern to waterfowl managers. This con dabbling duck use of these marshes and cern stems not only from the fact that found greatest duck concentrations in many pollutants cause mortality, but the fresh and intermediate types, which also because they affect bird behavior had lowest salinities. The saline type, and reproductive success and may cause which was adjacent to the coastline, had a deterioration of winter habitat. highest salinity and lowest dabbling duck The discharge of lead shot into the use. environment by hunters is a form of Retreat and advancement of vegeta pollution and occurs nationwide, but the tional types over a 25-year period were majority of deaths from lead poisoning determined by comparing a type map of are within the Mississippi Flyway (Stout the Louisiana coast in 1943 (O'Neil 1949) and Cornwell 1976).The gradual transfer with a type map of the area in 1968 from lead to steel shot offers a logical (Chabreck et al. 1968). Comparisons dis alternative for curtailing the problem. closed that the saline type remained Various other forms of pollution are unchanged in southwestern Louisiana reported in the literature, and most mor 137 WINTER HABITAT OF DABBLING DUCKS tality occurs on the wintering grounds. well known. The value of food for attract Oil spills are an important mortality ing birds was the basis for outlawing factor in waterfowl, but diving ducks are baiting in areas used for hunting. Also, the group most affected. The nature of the use of baits to lure ducks into traps is winter habitat used by dabbling ducks the most common capture technique used largely removes them from contact with by agencies banding birds. Management oil. An oil spill in winter habitat used by programs for ducks usually involve im dabbling ducks was investigated, but no provement of food supplies by artificial bird mortality was noted (Chabreck 1973) plantings or habitat manipulation to The oil did, however, act as a repellent increase growth of natural foods (Davi to ducks, and habitat use did not return son and Neely 1959, Givens and Atkeson to normal until 6 months after the spills. 1959). Numerous industrial pollutants and Impoundments were constructed on insecticides have been investigated to the 50,000-ha Rockefeller Wildlife Refuge determine their distribution in the in Louisiana during the mid-1950's as environment and effects upon dabbling habitat management for dabbling ducks. ducks (Hunt and Ewing 1953, Dustman Although less than 20% of the area was et al. 1971, Brunch and Low 1973, Long impounded, wintering duck populations core and Samson 1973, Heinz 1976, on the refuge increased from 75,000 to Pearce et al. 1976). Very often the water 400,000 birds as a result of the program, that enters drainage systems and wet and 80% of the ducks were in the im lands used by waterfowl has been used poundments. Vegetational sampling and reused many times and contains a disclosed that species important as duck variety of contaminants when it reaches foods made up 50% of the plants in the the birds. More effort is needed to impoundments but only 20% of those properly identify these problems and outside (Chabreck 1959). solve them (Friend 1975). Since the 1930's, grain and soybean fields have become an increasingly BIOLOGICAL ASPECTS OF more important component of the winter WINTER HABITAT habitat of dabbling ducks, particularly mallards, pintails, black ducks and,wood Food Availability ducks. Many birds have adapted to dry field feeding and have become dependent All major dabbling duck concentration upon grain and soybeans as a primary areas have one common component: food source of winter food (Madson 1964, is abundant and readily available. By Horn and Glasgow 1964). Mallards have removal of this essential element, an altered their traditional migrational and area quickly loses its attractiveness to wintering patterns in response to this dabbling ducks. Hawkins et al. (1946) immense food supply. Only with a deep noted a mass exodus of mallards from snow covering of habitats are some birds the Grand Prairie Region of Arkansas discouraged enough to depart for milder into Louisiana and Mississippi caused climates (Madson 1964). mainly by the shortage of food. The movement took place in spite of favor Diseases and Parasites able weather conditions and with spring close at hand. Problems of diseases and parasites The importance of providing preferred have no doubt plagued dabbling ducks in foods in adequate amounts for attracting winter habitats throughout history. and holding dabbling ducks on an area is Botulism had been responsible for water 138 WATERFOWL AND WETLANDS SYMPOSIUM fowl losses for many years before 1910, maintaining high productivity, the role but that year the first real concern was of winter habitat should not be over expressed about its effect on waterfowl looked. Dabbling ducks occupy winter populations (Jensen and Williams 1964). habitat for 7 or 8 months per year, and Since that time, considerable effort has the quality of the habitat may determine been placed on tracking outbreaks of the condition of birds returning to breed diseases and parasites and determining ing grounds the following spring. environmental conditions associated Conditions within the Atlantic Flyway with outbreaks. Bird losses may have should serve as a reminder to managers been overlooked in the past when habitat who fail to recognize the importance of was plentiful, but as habitat declines and wintering grounds. Because of tremen ducks become more crowded, losses be dous urban and industrial growth, many come more obvious. Problems have been former winter habitats in that flyway reported from all winter habitats. have been destroyed or have deteriorated The birds on restricted habitat have to the point where they are no longer also contributed to the problem. Crowd attractive to ducks (Addy 1964). In fact, ing of people or wildlife enhances the the destruction rate of wintering areas spread of contagious and infectious may exceed the loss of breeding grounds, diseases and parasites and causes stress and birds migrating southward in the within individuals that makes them fall may be adversely affected by over more vulnerable to various maladies. crowding on the few remaining attrac Inadequate food supplies and pollutants tive habitats. can disrupt body defense mechanisms, The impact of habitat alteration will alter host-parasite relationships, and vary among species of dabbling ducks. bring on still more disease problems The more adaptable species change with (Friend 1975). the times and seek out new habitats as The magnitude of disease and parasite former habitats are modified or de problems in dabbling ducks was investi stroyed. For example, clearing of bottom gated by Stout and Cornwell (1976) by land hardwoods for soybean farming analyzing reports and band data. They may have varying effects on different found that disease mortality in all water species. Mallards and wood ducks, which fowl accounted for 87.8% of the total previously used the habitat, will be reported non-hunting mortality. Botu forced to change habitats or seek similar lism was the major source of non-hunt habitat elsewhere. The mallard, being ing mortality, and dabbling ducks made more adaptable, may return to the same up 92% of the band recoveries attributed area and be equally at home in the soy to botulism. Predation loss was not listed bean field. The wood duck, however, as an important factor affecting water requires a forest environment and must fowl and represented only 0.1% of all move elsewhere to find similar habitat. non-hunting mortality reported. Similar habitat in other areas is usually occupied, and its use by displaced birds often results in a problem of overcrowd SUMMARY AND CONCLUSIONS ing. Each fall some 50 million dabbling Most literature dealing with continen ducks representing 10 species depart the tal population of dabbling ducks stresses northern breeding grounds and make the importance of breeding habitat for their way southward for the wintering maintaining the resource. Although ade season. Habitat requirements vary con quate breeding habitat is essential for siderably among species, and diversity of J39 WINTER HABITAT OF DABBLING DUCKS winter habitat must be maintained in general overview of these components; order to meet the needs of all species. however, to be useful to managers or Diversity should include not only an ade decision makers, all components must be quate representation of all habitat types, quantified to a level that permits reason but also an adequate distribution of all able predictions of habitat quality. types throughout the winter range. Future research should be designed to The winter habitat needs of all species identify the precise winter habitat of dabbling ducks cannot be evaluated requirements of dabbling ducks and the without full understanding of the habitat factors affecting habitat quality and to requirements of individual species. This establish mathematical values of each understanding should begin by charac habitat component for the purpose of terizing the physical, chemical, and biolo quality assessments. With this informa gical components of the habitats used by tion, winter habitat availability and each species. This paper has presented a needs can be determined more accurately. 140 WATERFOWL AND WETLANDS SYMPOSIUM LITERATURE CITED ADDY, C. E. 1964. Atlantic Flyway. Pages fica nee of polychlorinated biphenyls in 167-184 in J. P. Linduska, ed. Waterfowl the environment. Trans. N. Am. Wildl. tomorrow. U.S. Government Printing Nat. Resour. Conf. 36:118-133. Office, Washington, D.C. EDMINSTER, F. C. 1964. Farm ponds and BELLROSE, F. C. 1976. Ducks, geese and waterfowl. Pages 399-407 .n J. P. Lindu swans of North America. Stackpole ska, ed. Waterfowl tomorrow. U.S. Books, Harrisburg, PA. 544pp. Government Printing Office, Washing BRUNCH, T. D., AND J. B. LOW. 1973. Ef ton, D.C. fects of dieldrin on chromosomes of semi ENSMINGER, A. B., AND L. G. NICHOLS. domestic mallard ducks. J. Wildl. Manage 1957. Hurricane damage to Rockefeller 37(1):51-57. Refuge. Proe. Southeastern Assoc. Game BURGESS, H. H. 1969. Habitat management and Fish Commissioners 11:52-56. on a mid-continent waterfowl refuge. J. FRIEND, M. 1975. New dimensions in Wildl. Manage. 33(4):843-847. diseases affecting waterfowl. Proc. Int. CHABRECK, R. H. 1959. Coastal marsh Waterfowl Symp. 1:155-162. impoundments for ducks in Louisiana. GIVENS, L. S., AND T. Z. ATKESON. 1959. Proc. Southeastern Assoc. Game and Fish Farming for waterfowl in the south Commissioners 14:24-29. eastern United States. U.S. Fish Wildl. __ . 1970. 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STICKEL, L. J. Industrial pollution and Michigan water BLUS, W. L. REICHEL, AND S. N. WIE fowl. Trans. N. Am. Wiidl. Conf. 18:360 MEYER. 1971. The occurrence and signi 368. 141 WINTER HABITAT OF DABBLING DUCKS JENSEN, W. I., AND C. S. WILLIAMS. 1964. PALMISANO, A. W. 1972. Habitat prefer Botulism and fowl cholera. Pages 333-341 ence of waterfowl and fur animals in the in J. P. Linduska, ed. Waterfowl tomor northern Gulf Coast Marshes. Pages 163 row. U.S. Government Printing Office, 190 in R. H. Chabreck, ed. Coastal marsh Washington, D.C. and estuary management symposium. LONGCORE, J. R., AND F. B. SAMSON. Louisiana State Univ., Baton Rouge. 1973. Eggshell breakage by incubating black ducks fed DDE. J. Wildl. Manage. PEARCE, P. A., I. M. PRICE, AND L. M. 37(3):390-394. REYNOLDS. 1976. Mercury in waterfowl from eastern Canada. J. Wildl. Manage. LYNCH, .J. J. 1964. Weather. Pages 283-292 40(4):694-703. in J. P. Linduska, ed. Waterfowl tomor row. U.S. Government Printing Office, PENFOUND, W. T., AND E. S. HATHAWAY. Washington, D.C. 1938. Plant communities in the marsh MADSON, J. 1964. The cornfielders. Pages land of southeastern Louisiana. Ecol. 425-434 in J. P. Linduska, ed. Waterfowl Monogr.8(1):1-56. tomorrow. U.S. Government Printing STOUT, I. J., AND G. W. CORNWELL. 1976. Office, Washington, D.C. Nonhunting mortality of fledged North MACNAMARA, L. G. 1957. Potentials of American waterfowl. J. Wildl. Manage. small waterfowl areas. Trans. N. Am. 40(4):681-693. Wildl. Conf. 22:92-96. WHITE, W. M., AND G. W. MALAHER. 1964. MARTIN, A. C., AND F. M. UHLER. 1939. Reservoirs. Pages 381-389in J. P. Lindu Food of game ducks in the United States ska, ed. Waterfowl tomorrow. U.S. Gov and Canada. U.S. Dept. Agric. Tech. Bull. ernment Printing Office, Washington, 634.308pp. D.C. NELSON, N. F. 1954. Factors in the develop WILLIAMS, D. A. 1964. Waterfowl habitat ment and restoration of waterfowl habi under U.S. agricultural programs. Trans. tat at Ogden Bay Refuge Weber County, N. Am. Wildl. Conf. 29:246-254. Utah. Utah Dept. Fish Game Publ. 6. 87pp. WILLS, D. W. 1965. An investigation of some O'NEIL, T. 1949. The muskrat in the Louisi factors affecting waterfowl and water ana coastal marshes. Louisiana Wild Life fowl habitat on Catahoula Lake, Louisi and Fisheries Commission, New Orleans. ana. M.S. Thesis. Louisiana State Univ., 159pp. Baton Rouge. 82pp. 142 WATERFOWL AND WETLANDS ANINTEGRATED REVIEW Proc. 1977Syrnp., Madison, WI, NC Sect., The Wildlife Society, T. A. Bookhout, ed. Published in 1979 SYMPOSIUM SUMMARY AND COMMENTS ON THE FUTURE OF WATERFOWL AND WETLANDS JOHNP. ROGERS Office of Migratory Bird Management, U.S. Fish and Wildlife Service, Washington, D.C. 20240 This symposium on waterfowl and wetlands. wetlands has been specifically aimed at An obvious starting point for an over reviewing recent and ongoing stud ies all review of the biology of dabbling relating to habitat dynamics and habitat ducks is a description of how the various requirements of North American dab species distribute themselves during the bling ducks. It has the purpose of con breeding season in the vast and complex tributing to a better understanding of array of wetland habitats in North the state of our knowledge of these America, and how they relate to these subjects and, perhaps, a better perspec habitats in terms of space, time, and tive about current and future research other impinging factors. The first part of and management needs. this descriptive effort was ably handled The papers presented here today by Frank Bellrose, whose unmatched provide us with a wealth of information knowledge and experience with North and experience gained from many years American waterfowl is one of our most of dedicated field and laboratory work. valuable assets. His paper shed addi They contain much more than can be tional light on hew important the so fully digested and absorbed in the short called prairie pothole country is to breed time available to us now. In these closing ing dabblers, and why and how other comments, therefore, I will not attempt segments of the breeding range differ an in-depth analysis of them. Instead, I from it in quantity and quality of habi will briefly review what seem to me to be tat, as well as in duck populations. some of the main points, discuss the re For the second part of this effort search trends that seem evident and how Trauger and Stoudt drew on the impor they relate to management needs, and, tant information gleaned from more finally, make a few personal observa than 25 years of continuous observations tions on the future of waterfowl and of the fortunes of ducks on 3 specific 143 SYMPOSIUM SUMMARY study areas in the prairies and parklands on the importance of animal food to the of western Canada. They described how reproductive potential of free living a combination of weather cycles, intensi prairie ducks, and how lack of this fied land use, differences between species important source of protein can affect in breeding chronology and possibly production and the quality of eggs. other factors, such as hunting pressure, Owen and Reinecke continued the have adversely affected local abundance, general topic by presenting a synthesis species composition, and reproductive of information about the energy require success. This paper is important as a case ments of breeding ducks with estimates history of what has happened in certain of the needs for daily energy intake and parts of the breeding grounds and could how it is expended. They emphasized the happen in others. extremely high energy demand on female John Kadlec reviewed the state of dabbling ducks during the egg-laying knowledge about the dynamics of nitro period - a situation where metabolic gen and phosphorus abundance and rates may approach maximum sustain cycles in wetland ecosystems, pointing able levels - and pointed out the many out their importance in the maintenance gaps in our knowledge about energy of wetland plant and animal communi needs of ducks in the wild. It is difficult ties, and the interrelationships that to over-estimate the potential value of appear to ex ist. This is an aspect of such information in helping managers natural wetland processes that has, so understand the carrying capacity of far, received too little attention and con breeding habitat. sideration by waterfowl managers. His Finally, Bruce Batt described individ suggestions about managing wetlands to ual variation among captive mallards in enhance the supplies and internal cycling laying dates, clutch size, and egg size but of these all-important nutrients warrant found these factors to be consistent from the attention of waterfowl managers in year to year in particular individuals. He relation to maintaining and improving suggested that this indicates the exis wetlands for waterfowl. tence of previously unrecognized varia Five of the 11 papers presented today tion within species in basic breeding dealt with factors influencing breeding strategy that may have a genetic basis. strategies. Indeed, they formed the most If so, this is a mechanism that could pro important part of the symposium in vide a means for mallards to adjust their terms of the attention devoted to one breeding strategy to long term changes general topic. Thus, Scott Derrickson in habitat conditions. It also merits con told us about differences in the behavior sideration in such practical matters as of pairs on breeding areas in relation to the interpretation of breeding population the status of the pair bond and breeding surveys. chronology, and how this may affect the Shifting attention to a different part breeding strategies of different species. of the life cycle, Harold Prince led us into Swanson, Krapu, and Serie described the labyrinths of metabolic rates as part food selectivity on the breeding grounds of his effort to shed light on the post by five species of dabblers and how the breeding behavior of dabbling ducks in birds were influenced both by nesting terms of energy and time budgets. He chronology and availability of food re pointed out the importance of this for sources. They stressed the importance of better understanding life history phe the entire wetland complex, rather than nomena and adaptive strategies. The a se lected part of it, to the quality of usefulness of such information for waterfowl breeding habitat. In a sepa practical management in the United rate but related paper Krapu expanded States is obvious when it is considered 144 WATERFOWL AND WETLANDS SYMPOSIUM that much of our wetland management different aspects of waterfowl biology, effort is aimed primarily at the main but the effort to relate the results to tenance and welfare of waterfowl during other research and management findings fall and winter rather than the breeding and problems. season. Yet, the distribution and move A great deal of attention was focused ments of waterfowl at these times are today on such matters as the factors often influenced more by events asso influencing continental breeding ground ciated with agricultural or other land use distribution, specific local habitat and trends than by purposeful waterfowl population relationships, social inter management. actions and breeding biology, feeding Fredrickson and Drobney continued behavior and nutrient factors in relation the discussion of post-breeding water to reproductive biology, bioenergetics in fowl biology, pointing out the general relation to distribution and ecology, the lack of attention accorded to this part of management implications of individual the life cycle. They identified some ob variation in nesting behavior within a vious and some not so obvious species species, and habitat factors in relation differences that appear characteristic of to the ecology of post-breeding and win the post-breeding period, and noted the tering waterfowl. These may appear at inherent difficulty of studying and ac first glance to be quite separate and quiring information about waterfowl diverse elements, but they are all part of during this period. We must agree with the fabric of waterfowl biology; it is our their view that such information is continuing task to strive to see the whole essential and long overdue for better as well as the parts. understanding of habitat requirements, Another important aspect is what food resources, feeding ecology, and non appears to be a growing interest in the hunting mortality. biology of waterfowl during the post In the final paper, Bob Chabreck breeding and wintering periods. An discussed factors influencing the quality effort to understand the factors affecting of wintering dabbling duck habitat based waterfowl in this portion of their life on studies and observations in Louisiana, cycle, and to apply this knowledge, is which contains probably the greatest and essential to a balanced research and most important expanse of wintering management program. We must not habitat in North America. He pointed overlook the fact that one of the most out that dabbling ducks spend a major important roles for the United States in portion of their annual life cycle on the the continental management picture is to wintering grounds and that the quality provide essential post-breeding and win of winter habitat must be an important tering habitat. factor in determining how well the birds These aspects seem to me to indicate are prepared for breeding. We have not a more definite move toward viewing yet begun to understand in detail the waterfowl in terms of their total environ influence of winter habitat conditions in ment and their total biology than has the life cycles of the different species of been evident in the past. I believe this is waterfowl. The experience and know not only desirable but essential if we are ledge already acquired by biologists in to continue to improve our understand Louisiana and elsewhere should provide ing of dabbling ducks and other water a point of departure for the necessary fowl popuiat.ions, and our ability to studies of the future. manage them. Some of the most basic One of the important things about this and far-reaching management problems symposium is not just the variety of are unlikely to be resolved with any other thrusts toward better understanding of approach. 145 SYMPOSIUM SUMMARY For example, let me briefly mention justifiably so. However, it may be worth just two problem areas that are of parti while to remind ourselves that there are cular interest and concern to manage other perspectives on the future. I believe ment at the present time, and that I be that with possibly a few specific excep lieve will require this kind of approach. tions waterfowl are remarkably resilient The first concerns annual mortality and creatures that are likely to be here in its role in regulating population size. abundance long after you and i are gone. This has long been a major area of It is often difficult for people like us, research effort, and much progress has who are so completely immersed in the been made. But from a practical manage day-to-day problems and difficulties of ment standpoint, we need to know much waterfowl management and research, to more about the nature and magnitude of keep in mind that we still have waterfowl hunting and non-hunting mortality, how in sufficient abundance to provide rea they are interrelated, and their relative sonably good opportunities for hunting impact on the population status of dif and viewing. In some places, and with ferent species and populations of water some species, abundance today is far fowl. The importance of this is brought greater than in historical times. This in home to us each year when we seek to itself is the cause of management prob establish reasonable hunting regulations. lems of major concern as, for example, The second concerns the relationship with some present day Canada goose between populations and food resources. populations. What are the roles played by food sup In some ways this is really quite re plies and availability in regulating markable. I wonder how many would waterfowl population size, distribution, have anticipated, 30 years ago, that and health? The need for information in waterfowl would be as abundant today this area is great, not only in relation to as they are? This is not to say that we breeding habitat but also in relation to don't have serious problems in maintain the management of 'wintering habitat. ing waterfowl in abundance. We have We have barely scratched the surface of plenty, and there is no reason for anyone this aspect of waterfowl management. to be complacent about them. But the Answers to these questions are ex problems of assuring that waterfowl will tremely important for determining the remain at least as abundant in the im degree to which we can improve and mediate future as they are today are not refine the management of waterfowl insoluble. One of the most important generally, and by species and population factors in this regard is the great reser units within species. They can only come voir of public interest in the welfare of from broadly based and well integrated waterfowl, and public support for pro studies. No one need expect that an grams to maintain them in relative understanding of how waterfowl fit into, abundance. and relate to, their total environment The fact that this is a matter of na will evolve easily or quickly, but the tional policy at the highest level, as understanding is essential to manage spelled out in formal international ment and the effort to obtain it should be treaties and commitments with such encouraged. countries as Canada, Mexico, Japan, and, In regard to the future of waterfowl most recently, the Soviet Union is a and wetlands, it seems to be customary reflection of the depth of this public to take a very pessimistic attitude. The interest and support, literature is full of dire warnings about I think the future of waterfowl in this the imminent decline and fall of North country will be greatly dependent on how American duck populations - perhaps well we waterfowl managers and re 146 WATERFOWL AND WETLANDS SYMPOSIUM searchers do our job and maintain our Lynn Greenwalt, Director of the U.S. credibility with the public as responsible Fish and Wildlife Service, recently and objective scientists and administra pointed out that the option of letting tors. I'm sure it is no secret to many in nature take its course was set aside more this audience that waterfowl, manage than 200 years ago in North America. ment today is being criticized and occa If we want waterfowl in abundance in sionally ridiculed by some as archaic, the future, we're going to have to manage unnecessary, and even inhumane. In for it. Most of us know this, and one of part, this attitude seems to be motivated our most important responsibilities is by a strong and growing anti-hunting to make our knowledge believable and sentiment. But, there also seems to be a understood by the public. This task is at view that if managers would just leave least as important as the continuing ef things alone and let nature take care of fort to improve our understanding and fish and wildlife, everything would be our management of these most valuable just fine. and attractive birds. 147 148 NOTES 149 NOTES 150