I
ILLINOIS NATURAL HISTORY SURVEY
M§'fX £^L%Th Print fd by Authority of the State of Illinois
Lead Poisoning as a Mortality Factor in Waterfowl Populations
FRANK C. BELLROSE
STATE OF ILLINOIS • William G. Stratton. Governor DEPARTMENT OF REGISTRATION AND EDUCATION • Vera M. Binm, Direefr NATURAL HISTORY SURVEY DIVISION • Harlow B. Mills, Chief .7^) ILLINOIS NATURAL HISTORY SURVEY Bulletin
Volume 27, Article 3 Printed by Authority of May, 1959 the State of Illinois
Lead Poisoning as a Mortality Factor in Waterfowl Populations
FRANK C. BELLROSE
STATE OF ILLINOIS • William G. Stratton, Governor DEPARTMENT OF REGISTRATION AND EDUCATION • Vera M. Binks, Director
NATURAL HISTORY SURVEY DIVISION • Harlow B. Mills, Chief Urbana Illinois STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION William G. Stratton, Governor Vera M. Binks, Director BOARD OF NATURAL RESOURCES AND CONSERVATION \'era M. Binks, Chairman; A. E. Emerson. Pli.D., Biology; Walter H. Newhouse, Ph.D., Geology. Roger Adams, Ph.D., D.Sc, Chemistry: Robert H. Anperson, B.S.C.E., Engineering: W. L. Everitt, E.E., Ph.D., Representing the President oj the University oj Illinois: Delyte W. Morris, Ph.D.. Piesitlent of Southern Illinois University
NATURAL HISTORY SURVEY DIVISION, Urbano, Illinois SCIENTIFIC AND TECHNICAL STAFF Harlow B. Mills, Ph.D., Chief Bessie B. East, M.S., Assistant to the Chiel
Section of Economic Entomology Section of Aquatic Biology— continued George C. Decker, Ph.D., Principal Scientist and Head RuHAKD E. Bass, Field Assistant ]. H. Bigger, M.S., Entomologist Robert D. Crompton, Field Assistant L. L. English, Ph.D., Entomologist .Arnold W. Fritz, B.S., Field Assistant* Willis N. Bruce, Ph.D., Associate Entomologist David J. McGinty, Field Assistant* Norman Gannon, Ph.D., Associate Entomologist W. H. Luckmann, Ph.D., Associate Entomologist Section of Applied Botany and Plant Pathology
Ronald H. Meyer, M.S., Assistant Entomologist I. Cedric Carter, Ph.D., Plant Pathologist and Head John D. Paschke, Ph.D., Assistant Entomologist J. L. Forsberg, Ph.D., Plant Pathologist John P. Kramer. Ph.D.. Assistant Entomologist G. H. BoEWE, M.S., Associate Botanist Robert Snetsinger, M.S., Field Assistant RouERT A. EvERS, Ph.D., Associate Botanist Carol Morgan, B.S.. Laboratory Assistant Robert Da.n Neely, Ph.D., Associate Plant Pathologist Eugene M. Bravi, M.S.. Research Assistant E. B. Hi.MELicK, M.S., Assistant Plant Pathologist Richard B. Dysart, B.S., Technical Assistant Walter Hartstirn, Ph.D., Assistant Plant Pathologist Reginald Roberis. A.B., Technical Assistant D. F. ScHOENEWEiss. Ph.D., Assistant Plant Pathologist James W. Sanford. B.S., Technical Assistant Rovenia F. Fitz-Gerald, B.A., Technical Assistant Earl Stadelbacher. B.S., Technical Assistant Sue E. Watkins. Technical Assistant Section of Wildlife Research Extension Specialist in Entomology* H. B. Petty-, Ph.D , Thomas G. Scott, Ph.D., Game Specialist and Head Stevenson Moore, III, Ph.D., Extension Specialist in Ralph E. Yeatter, Ph.D., Game Specialist Entomology* Carl O. Mohr, Ph.D.. Game Specialist Zen AS B. Noon, Jr., M.S., Research Assistant* F. C. Bellrose, B.S., Game Specialist Clarence E. White, B.S., Research ,4ssistant* H. C. Hanson, Ph.D., Associate Game Specialist John Arthur Lowe, M.S.. Research Assistant* Richard R. Graber, Ph.D., Associate Wildlife Specialist J. David Hoffman, B.S., Research Assistant* Ronald F. Labisky', M.S., Assistant Wildlije Specialist Carlos A. White, B.S., Research Assistant* Frances D. Robbins, B.A., Technical Assistant Roy E. McLaughlin, B.S., Research Assistant* Virginia A. Langdon. Technical Assistant KousKOLEKAS, M.S., Research .Assistant* CosTAS Howard Crum, Jr., Field Assistant Research Assistant* Louise Zingrone, B.S., John L. Roseberry', B.S., Technical Assistant Mary E. Mann, R.N., Research Assistant* Rexford D. Lord, D.Sc, Project Leader* Frederick Greeley, Ph.D., Project Leader* Section of Faunistic Surveys and Insect Identification Glen C. Sanderson, M.A., Project Leader* H. H. Ross, Ph.D., Systematic Entomologist and Head Iack A. Ellis, M.S., Assistant Project Leader* Milton W. Sanderson, Ph.D., Taxonomist Thomas R. B. Barr, M.V.Sc, M.R.C.V.S.. Research Assistant* Lewis J. Stannard, Jr., Ph.D., Associate Taxonomist Philip W. Smith, Ph.D., Associate Taxonomist Bobbie Joe Verts. M.S., Field Mammalogist* Leonora K. Gloyd, M.S., Assistant Taxonomist Erwin W. Pearson, M.S., Field Mammalogist* H. B. Cunningham. M.S.. Assistant Taxonomist Keith P. Dauphin, Assistant Laboratory Attendant* Edward L. Mockford, M.S., Technical Assistant Gary P. I.mel, Assistant Laboratory Attendant* Thelma H. Overstreet, Technical Assistant Section of Publications and Public Relations Section of Aquatic Biology James S. Ayars, B.S.. Technical 'Editor and Head George W. Bennett, Ph.D., Aquatic Biologist and Head Blanche P. Young, B.A.. Assistant Technical Editor William C. Starrett, Ph.D., Aquatic Biologist Diana R. Braverman, B.A., Assistant Technical Editor R. W. Larimore, Ph.D., Aquatic Biologist William E. Clark, Assistant Technical Photographer David H. Buck, Ph.D., Associate Aquatic Biologist Marguerite Verley, Technical Assistant Robert C. Hiltibran, Ph.D., Associate Biochemist Donald F. Hansen. Ph.D., Assistant Aquatic Biologist Technical Library William F. Childers, M.S., Assistant Aquatic Biologist Ruth R. Warrick, B.S., B.S.L.S., Technical Librarian Marifran Martin, Technical Assistant NhLL Miles, M.S., B.S.L.S.. Assistant Technical John C. Cralley, B.S., Field Assistant Librarian
CONSULTANTS: Herpetolocy, Hobart M. Smith, Ph.D., Professor oj Zoology, University oj Illinois: Parasitology, Norman D. Levine, V\\.1l)., Professor of Veterinary Parasitology and of Veterinary Research, University of Illinois: Wildlife Research, Willard D. Klimstra, Ph.D., Assistant Professor of Zoology and Director of Co-operative Wildlife Research, Southern Illinois University.
Employed on co-operative projects with one of several agencies: University of Illinois, Illinois Agricultural Extension Service, Illinois Department of Conservation, United States Army Surgeon General's Office, United States Department of Agriculture, United States Fish and Wildlife Service, United States Public Health Service, and others.
This paper is a contribution from the Section of Wildlife Research.
f86180—5,500— 10-58) CONTENTS
Acknowledgments 236 Lead Poisoning Die-Offs 236 Early Die-Offs 238 Recent Die-Offs 239 Atlantic Flyway 239 Mississippi Flyway 242 Central Flyway 243
Pacific Flyway 244
Frequency of Die-Offs 245
Seasons of Die-Offs 246 Species Affected by Dic-Offs 247
Incidence of Lead Shot in Die-( )ffs 247 Availability of Lead 249 Ingested Lead Shot in Migrating Ducks 254
Shot in Live-Trapped Ducks 254
Shot in Ducks Bagged by Hunters 258
Variations in Shot Incidence Among Species 259
Regional Variations in Shot Incidence 261
Periodic Variations in Shot Incidence 265
Incidence of Various Shot Levels 268 Lead in Wild Mallards Dosed and Released 269
Effect of Lead on Vulnerability to Hunting 270
Effect of Lead on Migration Rate 272 Effect of Lead on Year-of-Banding Mortality Rate 274 Preventing Lead Poisoning 276 Discussion 279 Summary 283 Literature Cited 287
Photographs not otherivisr crrditrd arc by fVilliam E. (Uark or by Charles L. Scott. A few of the 2,000 wild mallards that were victims of a lead poisoning outbreak near Grafton, Illinois, in January, 1948. (Photograph from Western Cartridge Company.) Lead Poisoning as a Mortality Factor
in Waterfowl Populations
FRANK C. BELLROSE
mortality resulting from lead realized. There is urgent need to ascer- THEpoisoning in populations of wild tain the effects of the lead shot used in waterfowl has been a cause of con- hunting." cern to conservationists for many years. These remarks point up the generally This concern has grown out of the knowl- recognized need for further appraisals of edge that lead poisoning is of common oc- the problem, which was brought home to currence among waterfowl, that this poi- officials of the Illinois Natural History soning results from the ingestion of lead Survey and Western Cartridge Company by the birds in their feeding, and that (the latter now the Winchester- Western large numbers of lead pellets fired from Cartridge Division of Olin Mathieson the guns of hunters lie in lakes and Chemical Corporation) at the time of a marshes visited by waterfowl. publicized die-off of wild ducks, frontis- Phillips & Lincoln (1930:166), over piece, near Grafton, Illinois, in January
two decades ago, stated : "From this ac- of 1948 (Jordan & Bellrose 1951:10-1). count it will be seen that lead poisoning As a result of a common interest in the due to eating shot is of common occur- problem of lead poisoning in waterfowl, rence, and it seems reasonable to presume the two groups supported a joint research that the disease will continue and even project embracing the following objec- increase in the great ducking marshes of lead tives : ( 1 ) evaluation of losses from the country. The ultimate conclusions as poisoning in wild waterfowl, (2) in- to its effect upon the supply of waterfowl vestigation of lead alloys and other metals are hazardous to imagine," A few years as materials for possible use as nontoxic later Dr. E. C. O'Roke of the Univer- shot, and (3) determination of the phys- sity of Michigan was quoted in Michigan iological effects of lead poisoning in wa- Waterfowl Management (Pirnie 1935: terfowl.
75-6) as follows: "Considering the enor- The present paper is devoted primarily mous quantity of lead that there must be to the evaluation of losses resulting from in the vicinity of blinds that have been lead poisoning in wild waterfowl popula- shot over for decades, it is reasonable to tions. Two reports have been published conclude that the potential danger from which presented preliminary findings on lead poisoning is great and should be con- this subject (Bellrose 1951; Jordan & sidered in any waterfowl management Bellrose 1951). Efforts to develop a non- program. In the writer's opinion lead poi- toxic shot were treated in a paper dealing soning is the disease which takes the with the value of various shot alloys in greatest toll of adult ducks in this section relation to lead poisoning (Jordan &
of the country." Bellrose 1950) ; additional data on this This theme was reiterated by Cottam subject are presented herein. Findings as (1949:339-40) who, in discussing fur- to the physiological effects of lead poison- ther needs in wildlife research, suggested ing on captive waterfowl have been dis- that "direct and indirect effects of lead cussed in a paper bv Tordan & Bellrose shot in the digestive tracts of birds may (1951). be an exceedingly important stumbling The approach toward evaluating the block in the restoration of waterfowl. At importance of lead poisoning in wild
the close of the hunting season live birds waterfowl was threefold : ( 1 ) appraisal are carrying in their bodies an alarming of the incidence and magnitude of water- amount of lead, and this condition may be fowl die-offs resulting from lead poison- much more widespread than we have ing, (2) appraisal of the incidence of [235] ;
2.?6 Illinois Natural History Survey Bulletin Vol. 27, Art. 3
ingested lead shot among waterfowl popu- Many persons provided information on lations in fall and early winter, and (3) waterfowl die-offs resulting from lead
appraisal of waterfowl losses resulting poisoning. I especially wish to thank
from the ingestion of various quantities of Richard E. Griffith, John J. Lynch, lead shot per bird. John W. Perkins, and Edward B. Davis of the United States Fish and Wildlife ACKNOWLEDGMENTS Service, and Richard K. Yancey and Morton M. Smith of the Louisiana Wild The writer is most grateful to the Life and Fisheries Commission for their man\ persons in various parts of the excellent co-operation. North American continent who furnished Edwin R. Kalmbach and Arnold L. material and data. W^ithout their aid, it Nelson of the United States Fish and would have been impossible to appraise Wildlife Service provided suggestions and the importance of lead poisoning on such unpublished reports on lead poisoning in an extensive basis. waterfowl. Johnson A. Neff of the same The sources of much of the informa- agency submitted an unpublished report tion outside of Illinois are acknowledged on band recoveries from experimental in the text or tables. However, the mallards, some untreated and some dosed sources of material and data related to with six No. 6 shot pellets each, near the occurrence of lead shot in waterfowl Denver, Colorado. gizzards have been so numerous as to Dr. Harlow B. Mills, Chief of the Illi- make such acknowledgment cumbersome. nois Natural History Survey, and the Acknowledgment is made here to those late Charles H. Hopkins and Ray persons who sent 100 or more waterfowl Holmes, both of Olin Mathieson Chemi- gizzards for examination: Harold M. cal Corporation, who initiated this study Swope, Colorado; E. B. Chamberlain, as a result of their interest in a die-off of Jr., Florida; William P. Baldwin, Jr., wild ducks near Grafton, Illinois, in Georgia and South Carolina; Robert L. 1948, continued their interest and aid Salter, Idaho; James D. McCall and throughout the study. Dr. Thomas G.
Russell E. Mumford, Indiana ; Rich- Scott, Head of the Survey's Wildlife Re- ard K. Yancey and Charles W. Bosch, search Section, and Mrs. Frances Rob-
Louisiana ; Howard L. Mendall, Maine bins, Dr. Ralph E. Yeatter, and Dr. Gordon T. Nightingale and Dave Grice, Carl O. Mohr, all of that section, gave Massachusetts; Forrest B. Lee, Minne- many helpful suggestions which improved sota; Harvey Miller, Nebraska; Fred E. both the study and the paper. John C. Wright, Nevada; T. Stuart Critcher and Dear and Charles E. Gillham of the Olin Yates M. Barber, Jr., North Carolina; Mathieson Chemical Corporation helped Brandt V. Hjelle, North Dakota; Wil- many times in many ways. James S. Ayars
liam B. Morse, Oregon ; Ray Murdy and of the Natural History Survey edited the Clair T. Rollings, South Dakota; J. R. manuscript. Singleton. Texas; Allen G, Smith. Utah. Without the financial assistance pro- The following biologists contributed vided by Olin Mathieson Chemical Cor- data on the incidence of ingested lead shot poration, much of this study would have found in waterfowl gizzards examined been impossible. primarily for food contents: Ian McT. Cowan, British Columbia; Carol M. Fer- LEAD POISONING DIE-OFFS rel and Howard R. Leach, California E. B. Chamberlain, Jr., Florida; Rich- The most dramatic expressions of lead ard K. Yancey, Louisiana; Howard L. poisoning in waterfowl are die-offs in
Mendall, Maine ; Leroy J. Korschgen which large numbers of birds in relatively
and Charles E. Shanks, Missouri ; Donald small areas perish in short periods of D. Foley, New York; T. Stuart Critcher, time. Most of those persons who are se-
North Carolina ; Charles K. Rawls, Jr., riously concerned about lead poisoning
Tennessee ; Allen G. Smith, Utah ; Rob- among waterfowl have been convinced of ert G. Jeffrey and Charles F. Yocom, the importance of the malady through Washington. witnessing one or more die-offs. Because May, 1959 Bellrose: Lead Poisoning in Waterfowl 237 of its emotional impact on any person Three approaches have been made by who sees it, a waterfowl die-off is an the author of this paper in evaluating the event that is remembered and chronicled importance of die-offs among waterfowl for a number of years. in the United States: (1) a study of the
Fig. 1. — Opened duck gizzards and the ingested lead shot they contained. Black spots on the horny linings of the gizzards mark areas of tissue destruction by lead salts.
Fig. 2.—Two mallard stoiriachs: the lower one from a lead-free duck, the upper from a lead-poisoned duck. The glandular stomach attached to the gizzard of the lead-poisoned mallard shows impaction of small grains. The impaction of food resulting from malfunctioning of the gizzard is one of the symptoms of lead poisoning in waterfowl. 238 Illinois Natural History Survey Bulletin Vol. 27, Art. 3
literature, (2) personal on-the-spot in- lina, stated that lead poisoning occurred vestigations of die-offs in Illinois and among waterfowl in Texas at Galveston, Louisiana, and (3) a canvass of state and at Stephenson Lake, and on Lake Sur- federal conservation agencies for recent prise. records of lead poisoning outbreaks among A half century ago, Bowles (1908: waterfowl. 312-3) recorded the loss of a number of In studying several large outbreaks of mallards {Anas platyrhynchos) from lead lead poisoning in Illinois, 1940-1954, and poisoning on the "Misqually" (presumably at Catahoula Lake, Louisiana, 1953, the Nisqually) Flats of Puget Sound, Wash- author and his associates undertook a tally ington. McAtee (1908:472) in the same of all dead and dying ducks found nnd of year gave an account of lead poisoning in feathers marking the demise of birds. canvasbacks (Aytliya valisineria) at Lake Rough compensations were made for areas Surprise, Texas. not covered and for the time of each sam- Wetmore (1919:2) reported that sev- pling in relation to the period of the out- eral whistling swans {Olor columbianus) break. An estimate was made of the duck from Back Bay, Virginia, were examined population in each area. by the U. S. Biological Survey in Janu- Samples of dead and dying ducks were ary of 1915. Twenty-two to 45 shot pel- collected. These ducks were sexed, aged, lets were found in the gizzard of each weighed, and fluoroscoped. Fluoroscopic swan, indicating that the birds had been procedure was similar to that described affected by lead poisoning. He reported by Jordan & Bellrose (1950:158) and also that during the summers of 1915 and by Bellrose (1953:341). Examinations 1916 in the Bear River marshes of Utah were made of lead shot pellets in gizzards many mallards and pintails {Anas acuta) of a number of dead ducks and were were affected by lead poisoning. These found to agree closely with fluoroscopic ducks were found in the period June- findings. Gizzards from lead-poisoned September, and, although many died, the
ducks are shown in figs. 1 and 2. total was insignificant as compared with losses from other causes in the Bear River Early Die-OflFs marshes. Records of lead poisoning in North In discussing lead poisoning, Phillips American waterfowl date back to the lat- & Lincoln (1930:165-6) recorded an ter half of the nineteenth century. From instance in which "thousands" of ducks remarks made by Phillips & Lincoln were reported dying at Hovey Lake, In- (1930:164), it is assumed that lead poi- diana, in February, 1922, from an un- soning in waterfowl was known at least known malady that was later diagnosed as early as 1874. According to them, the as lead poisoning. The report they found March, 1894, issue of the American Field to be "much exaggerated." They ob- carried a note reporting that two lots of served that "Possibly the most serious con- ducks which were unfit for food (pre- dition exists in Louisiana, where duck sumably as a result of lead poisoning) mortality from this cause may sometimes were seized at Galveston, Texas. These be further complicated by internal para- ducks had been taken at Stephenson Lake, sites and possibly at times by lack of
where the disease had been noted for 20 food" ; that newspapers reported in Janu- years. ary of 1925 that "thousands" of ducks More than 60 vears ago, George Bird were dying in Louisiana, apparently from Grinnell (1894:112) and E. Hough lead poisoning, for all the specimens ex- (1894:117) reported in Forest and amined were found to have ingested lead Stream on some of the effects of lead poi- shot; and that large numbers of ducks soning on waterfowl as determined from died from lead poisoning in the Jacobs observations made during the winter of and Pecan Lake region of Arkansas in 1893-94. A few years later, Grinnell January of 1925. (1901:598-601), in addition to review- Van' Tyne (1929:103-4) reported ing his earlier account on the appearance that at Houghton Lake, Michigan, in and behavior of a sick goose and a sick April of 1928, greater scaups {Aythya swan at Currituck Sound, North Caro- marila) died from lead poisoning. Of 10 ;
May, 1959 Bellrose: Lead Poisoning in Waterfowl 239 stomachs examined by Van Tyne, most entirely upon unpublished accounts for contained 40 to 60 pellets of lead, and information up to 1937. Since that time one contained 80 pellets. Elsewhere in only a few reports have been published Michigan, Pirnie (1935:74—5) reported (Mohler 1945; Bellrose 1947; Ayars that the deaths of five Canada geese 1947; Yancey 1953) but, fortunately, {Branta canadensis) in Barry County in outbreaks have been recorded in letters the spring of 1933, and a similar loss in and reported by biologists of state conser- Cass County in April, 1935, apparently vation agencies and the U. S. Fish and were the result of lead poisoning. Wildlife Service. Munroe (1925:160) recorded that one Data on most of the known die-offs of adult trumpeter swan {Olor buccinator) waterfowl from lead poisoning for the and six cygnets had died from lead poison- period beginning with the winter of 1938- ing in British Columbia during the winter 39 and extending through the winter of of 1925. 1956-57 are summarized in table 1. These E. R. Kalmbach (unpublished report, data have been obtained by contacting all March 6, 1930, in files of U. S. Fish and state conservation agencies in the United Wildlife Service) observed a lead poison- States, as well as those in Ontario and ing die-off of ducks in the coastal marsh British Columbia, plus the following area south of Gueydan, Vermilion Par- branches of the U. S. Fish and Wildlife ish, Louisiana, in February of 1930. In a Service: Wildlife Refuges, Game Man- 200-acre rice field he found 199 dead agement, and Wildlife Research. Most ducks: namely, 120 pintails, 71 mallards, of the information has been obtained and 8 lesser scaups {Aythya affinis). from letters and file reports graciously Kalmbach believed that the toll in the rice made available by waterfowl biologists of field was greater than that found in any these agencies. other area of similar size, but that losses In addition to the information pre- occurred throughout 300 or more square sented in table 1, many details have been miles of marsh. Albert Bonin, a resident made available which could not readily of that area, told Kalmbach that sick be recorded in tabular form. Therefore, it ducks had been observed in the Florence seems advisable to give a flyway-by-flyway section for at least 30 years. In Benin's roundup of information on the occur- experience, the spring of 1921 marked the rence of waterfowl die-offs resulting from severest outbreak noted in that region. lead poisoning. Shillinger & Cottam (1937:399) re- Atlantic Flyway.— Lead poisoning corded the following waterfowl losses in waterfowl apparently is not an im- from lead poisoning, all in the fall and portant mortality factor in the Atlantic early winter of 1936: 8 ducks from the Flyway. The largest reported losses, table coast of North Carolina; 5 mallards 1, amount to about 600 Canada geese and from the Pamlico Sound area of Virginia whistling swans which were picked up 14 ducks from Delaware Bay; 12 ducks over a 10-year period in North Carolina, from northern Ohio; and 100 ducks, The following comments, from letters most of them mallards, from Boyd Lake, by waterfowl biologists in that flyway, Colorado. The same authors (1937:402) illustrate the paucity of reports of die- gave an account of a die-off of ducks at offs from this malady. Dr. C. H. D. the Sand Lake National Wildlife Refuge, Clarke (letter, April 4, 1955) of the On- South Dakota, during November and De- tario Department of Lands and Forests cember of 1935. Of 113 mallards exam- reported: "I know of no die-off worthy ined there by John J. Lynch, 103 were of the name from lead poisoning in On- deemed victims of lead poisoning. Deaths tario. From time to time we have picked of 6 other individuals, representing four up individual poisoned waterfowl at vari- species of ducks, were attributed to this ous places where they are concentrated." disease. Of the situation in Maine, Howard E. Spencer, Jr. (letter, March 28, 1955), Recent Die-Oflfs wrote: "I have no knowledge of any die- In this review of lead poisoning die- offs which could be associated in any way offs, it has been necessary to rely almost with lead poisoning." From Vermont, 2 ,
240 Illinois Xatural History Survey Bulletin Vol. 27, Art. 3
r^ c T3 A o , c/3 U- tr •- c.-= .£ c c . 5J O = <:^ C/5 rt 3— 1J " "^ re .- ^ I— ^ «j V3 O _2^ 'E rt O ., C/l c UJ3 • ° C/5 U « E A t: — o E S U5 i; = 2 OJ -c c j= C3N O jC uj C c< .£ 3-- ^ 'C « a, O ^- US O < lO (-0 V/-1 — O OO — 7. Q >X) o CN O vo O -^ cI oo O o + + + + + "^ o o c o o o O O On O O O O r^ o o o o o o O CO — O * O O <*• .—I ^ lo ^^ C: CS (^ O O ffl S O o o o o o o o o O o o o o o o o o o o f- o o CN o -/ « z «^ c II O O O o Sou; o"c" o 5 2 S o 5^ a: oO oC' 4J U 5 CO ? en tn 5 ^ CI. UJ S S ^ ° "2 >., 5/J Ml Xp '- -13-T3-T3 -. — T3 "O "^ T3 "O T3 t3 "O tS 'rt "O Ui Ut k- L. u r; u c3 ri ci r: rt en = = .E = R c« o. n u SSS uu^ %'%% SS SS S SuSu T *^2 _" ON fo O OO ON 3: ON ON O, , r-co On ON 'ON 0^ X, -yT .-1 On *"• -. ^- '^ hf. -. f^ r—- C *- u <^ c '.-r »j S ~. >•? < u -£ *-•' n bf) « — r: Qi i^-~'-5 0S P ..Si SI gu is: < May, 1959 Bellrose: Lead Poisoning in Waterfowl 241 ^^ -C (J 1/; .'^ Xt^ ^ """^ '^IB rt :s:-r c^. oj rt *• u t- .y O J. K u c -n: t^ c/) cU. o 3 c oj -a "^ ^— u ™^ a! u-i u *-' C ^CD 9 tlZOn X ^. S o o 242 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 William R. Miller (letter, May 19, ter. May 13, 1955), reporting from North "1 1955) reported: have on a few occa- Carolina, remarked : "To my knowledge sions seen what to my mind was a case of we have no records of losses in waterfowl death due to lead poisoninjz;." James A. populations as a result of lead poison. Un- Lee (letter, March 29, 1955) reported: doubtedly, such losses do occur from "As far as I can ascertain, we have never time to time." Dr. J. H. Jenkins (letter, had a waterfowl die-off in New Hamp- May 12, 1955) of the University of shire attributable to lead poisoning." Georgia wrote: "I don't know of a sin- Charles L. McLaughlin (letter, May 23, gle case of lead poisoning of waterfowl in 1955) reported: "I have no authentic rec- Georgia. For one thing, there is very lit- ords of ducks dying of lead poisoning in tle shooting over established marshes." E. Massachusetts, and it is my opinion that B. Chamberlain, Jr. (letter, April 22, this type of mortality is unimportant in 1955), reported concerning lead poison- the state. A few years ago reports of large ing: "So far as we have been able to de- scale mortality from lead poisoning in the termine, there have never been any large coastal wintering black ducks was re- scale losses of waterfowl in Florida due ported, but investigation revealed that the to this cause." mortality was due to starvation rather Mississippi Flyway.—All but three than lead." Ruth S. Billard (letter, May states in the Mississippi Flyway have re- 3, 1955) reported as follows for the Con- ported die-offs of waterfowl as a result of necticut State Board of Fisheries and poisoning from ingested lead shot, table 1. Game : "We are not aware of any water- Among the largest losses have been those fowl succumbing from lead poisoning." reported from Louisiana. The largest Thomas J. Wright (letter, April 26, die-offs in Louisiana have been at Cata- 1955) reported: "Rhode Island, to the houla Lake in La Salle Parish, where 20,- best of my knowledge, has never had any 300 ducks are estimated to have died waterfowl losses that could be attributed from lead poisoning in the period 1950- to lead poisoning." 1955. Lead poisoning among the water- From New York, Donald D. Foley fowl of Catahoula Lake probably dates (letter. May 3, 1955) wrote: "There are back farther than 1930, for E. R. Kalm- without doubt many instances of such poi- bach in his 1930 report (on file, U. S. soning in this state, particularly in late Fish and Wildlife Service) mentions a winter and early spring, of which we are duck malady as occurring in previous not aware. However, we feel that the years at that lake. over-all picture is not too serious as to di- The largest known single outbreak of rect mortality." L. G. McNamara (let- lead poisoning occurred in the Claypool ter, April 27, 1955) reported: "As far as Reservoir area near Weiner, Arkansas, we know, lead poisoning is not a problem between mid-December of 1953 and mid- in New Jersev." Robert E. Stewart (let- February of 1954. John W. Perkins (let- ter, May 21, 1955) of the U. S. Fish and ter, February 12, 1954), game agent for Wildlife Service, in referring to the the U. S. Fish and Wildlife Service, esti- Maryland marshes, reported: "On sev- mated that during that period 16,000 eral occasions, during the past years, div- ducks, most of them mallards, succumbed ing ducks which appeared unable to fly to lead poisoning. were collected and found to contain worn A similar die-off of mallards had pre- lead pellets." In Delaware, Everett B. viously occurred there in early February' Chamberlain (letter, April 11, 1955) of 1951. The die-off was investigated by knew of only two duck deaths which were John J. Lynch (letter, February 9, 1951) suspected to be from lead poisoning. of the U. S. Fish and Wildlife Service, In Virginia, C. P. Gilchrist, Jr. (let- who reported seeing over 50 carcasses on ter, June 20, 1955), expressed his belief less than 3 acres of the 1,300 acre reser- that some ducks are lost to lead poison- voir. He concluded that the casualties ing, but not in large enough numbers to "numbered in the thousands." Further- be brought to the attention of the Com- more, Lynch stated that a die-off of simi- mission of Game and Inland Fisheries. lar proportions occurred on the same res- Farther south, T. Stuart Critcher (let- ervoir in the winter of 1948-49. May, 1959 Bellrose: Lead Poisoning in Waterfowl 243 In Missouri, the largest reported die- die-off amounted to over 1,000 birds, ta- off of ducks from lead poisoning took ble 1. That one took place at Forney place at the Squaw Creek National Wild- Slough, in Fremont County, during the life Refuge, where 10,000 out of 150,000- winter of 1948. 205,000 mallards died during the winter Reported losses from lead poisoning of 1956-57. In the previous winter, 5,000 among waterfowl in the lake states of mallards out of the 200,000 on the ref- Minnesota, Wisconsin, and Michigan uge died from lead poisoning. Other die- have been minor, table 1. In Wisconsin, offs occurred there every winter at least small losses of whistling swans occurred as far back as 1945; reported mortality in the Green Bay area in the springs of varied from 50 to 300 victims per year. 1948-1954. L. R. Jahn (letter, February Additional die-offs of mallards occurred 16, 1955) reported that, although ducks at Dalton Cut-off in Chariton County in were victims of lead poisoning in both 1949 and at the Swan Lake National spring and fall, their losses had been spo- Wildlife Refuge in 1939, 1952, 1953, and radic. H. J. Miller (letter, February 1954. 23, 1955) wrote that Michigan had not Hovey Lake, Posey County, Indiana, known an appreciable die-off of ducks has been a trouble spot for many years. from lead poisoning since the taking of As mentioned earlier, Phillips & Lin- waterfowl records was begun in 1940. In coln (1930:165) reported ducks dying the spring of 1942, 16 whistling swans there from lead poisoning as far back as were found dead from lead poisoning on 1922. The largest die-off there in recent widely separated marshes of southeastern years, an estimated 1,000 ducks, took Michigan. In the winter of 1953-54, place during the winter of 1947-48 100 whistling swans and 75 mallards were (James D. McCall, letter, February 5, reported as dying from lead poisoning at 1955). Reported losses since then have the Shiawassee National Wildlife Refuge, been sporadic and rather small, except for near Saginaw (Richard E. Griffith, letter, the death of 219 Canada geese in 1953 April 1, 1955). and 120 in 1955-56 (Martin 1957:114). After studying the mortality in large Small die-offs, aggregating 678 birds, are populations of ducks wintering, 1949- reported to have occurred at Hovey Lake, 1952, on the Detroit River in Michigan. the Kankakee State Game Preserve area Hunt & Ewing (1953:362, 367) con- (Starke County), and the Willow Slough sidered lead poisoning to be of little im- State Game Preserve (Newton County) portance as a mortality factor. during January and February, 1955. In Ohio, lead poisoning has evidently Since 1947, wherever large numbers of been a minor problem, for Delmar Hand- mallards have wintered in central Illinois, ley (letter, April 28, 1955) stated that there have been some outbreaks of lead only a few ducks and geese had been found poisoning. Most of the reported die-offs afflicted by this disease. A suspected case have occurred on, or in the vicinity of, of lead poisoning in Tennessee waterfowl the Chautauqua National Wildlife Ref- was reported by Parker Smith (letter, uge, near Havana, where 13,000 ducks May 5, 1955) as affecting 40 or 50 mal- are estimated to have died from lead poi- lards along the Obion River in Februarv, soning in the period 1941-1957, table 1. 1954. The largest single outbreak of lead poison- In three states of the Mississippi Fly- ing among waterfowl of Illinois occurred way, Kentucky, Mississippi, and Alabama, there in January and February of 1957, lead poisoning losses have not been re- when an estimated 5,000 succumbed. The ported (letters: Frank Dibble, April 12, second largest die-off occurred at Stump 1955; W. Walter Beshears, Jr., May 9, Lake, north of Grafton, where 3,000 mal- 1955; and Alec Bumsted, March 1, lards were victims of lead poisoning in 1955), but some losses undoubtedly oc- January, 1948. cur in those states. In Iowa, sporadic outbreaks of lead poi- Central Flyway.—Although die-offs soning among ducks have been noted since of waterfowl from lead poisoning have 1936, according to Everett B. Speaker occurred at several places in the Central (letter, February 23, 1955), but only one Flyway, they have not been so large as — 244 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 those in the Mississippi Flyway, table 1. stances it is felt the shot was ingested Largest losses in the Central Flyway have prior to arrival." Griffith reported some been reported from the Sand Lake Na- fatalities among mallards at the Fort Peck tional Wildlife Refuge area of South Da- Game Range in Montana, where 5,000 to kota, where more than 10,700 mallards 17,000 winter. Elsewhere in Montana, succumbed to lead poisoning over a span Wynn G. Freeman (letter, April 23, of 10 winters. 1955) reported he had found no water- A large die-off of ducks reported in fowl suffering from lead poisoning. Lubbock County, Texas, during the win- Other waterfowl biologists in the Cen- ter of 1944 was a most unusual one. De- tral Flyway who have yet to find mor- tails were reported in a letter (June 18, tality in waterfowl from lead poisoning 1945) from Oscar L. Chapman, then As- are B. A. Fashingbauer (letter, February sistant Secretary of the Department of the 17, 1955), North Dakota; Robert L. Interior, to the Secretary of War, Henry Patterson (letter, February 8, 1955), Wy- L. Stimson. Excerpts are as follows: oming; and Levon Lee (letter, February "During the past winter approximately 19, 1955), New Mexico. 800 wild ducks were found dead at two Pacific Flyway.—The largest out- small lakes on the grounds of the Lub- breaks of lead poisoning among waterfowl bock Army Air Field, Texas. Field of the Pacific Flyway have been reported studies conducted by the Fish and Wild- from California, table 1. In 1939, ducks life Service of this Department revealed estimated at 9,500 died from lead poi- that these losses were due primarily to soning in the Central Valley, San Fran- lead poisoning resulting from ingestion of cisco Bay, and Suisun Bay areas of Cali- lead shot which drop into one of these fornia, table 1, but it is not known to lakes during skeet practices. Studies con- what extent die-offs approach this number ducted by Army personnel indicated that every year, for the problem was investi- 80 per cent of the dead ducks examined gated in detail in only that j^ear by the contained lead pellets in their gizzards. California Department of Fish and Game. ... It is estimated that the annual loss In the winters beginning in 1944 and end- from the two lakes is between 5,000-10,- ing in 1954, 4,000 ducks were estimated 000 ducks, many of which perish on their to have become victims of lead poisoning northward migration. This estimate is at the Salton Sea National Wildlife Ref- substantiated by numerous reports of ema- uge in southern California. ciated dead and live ducks being found or Both the Tule Lake and the Lower seen in areas north of Lubbock." Klamath National Wildlife refuges in In Nebraska, George V. Schildman northern California, according to Rich- (letter, March 5, 1955) reported siz- ard E. Griffith (letter, May 17, 1955), able die-offs of blue geese (Chen caeru- have sections heavily shot over, and yet lescens) and lesser snow geese {Chen hy- reported losses from lead poisoning have perborea) from lead poisoning, table 1. been surprisingly low. In regard to loss of ducks, he stated: From Utah, Noland F. Nelson (letter, "The numerous rainwater basins in Clay, February 19, 1955) reported regarding Fillmore, and York counties provide some lead poisoning: "During the past 10 years losses each spring. . . .The losses are com- of waterfowl management work on Utah's monplace, but—to my knowledge marshlands, I have observed no large die- haven't been conspicuous and concen- offs of waterfowl resulting from lead poi- trated. However, these basins cover an soning. However, a few lead poisoning extensive area, and the total loss may be losses have been recorded every year. considerable." These recorded losses were almost always According to Richard E. Griffith (let- during the winter and early spring ter, April 1, 1955) : "Minor losses have months on some of the areas of heavy I been reported from the Salt Plains Ref- shooting around Great Salt Lake. . . . uge (Oklahoma), usually in single iso- A few emaciated mallard, pintail, shov- lated cases. An occasional bird with lead eler, and whistling swan have been exam- poisoning is picked up on other refuges ined almost every winter and a large per throughout the Southwest, but in most in- cent have contained ino;ested lead shot. May, 1959 Bellrose: Lead Poisoning in Waterfowl 245 The keeper of a local aviary rescued 33 agement Area located near Fallon, Ne- sick whistling swans one winter and 28 vada. This is our largest public hunting died from lead poisoning." area and bears the bulk of the waterfowl In discussing losses of waterfowl from shooters within the state." lead poisoning at the Bear River Migra- In Arizona, no losses of waterfowl tory Bird Refuge, Utah, Richard E. Grif- from lead poisoning have been reported fith (letter, April 1, 1955) emphasized during the past 10 years, according to that the loss cited, table 1, was a mini- Wesley B. Fleming (letter, February 8, mum one and should not be construed as 1955). a reliable indicator of total mortality. He Undoubtedly not all the outbreaks of reported that outbreaks of lead poisoning lead poisoning among waterfowl during occurred when ice restricted the birds to the past decade have been reported. How- a limited feeding area. The development ever, it is believed that outbreaks dis- of this situation was most apparent among cussed in this paper include the most im- the 10,000-12,000 whistling swans win- portant die-offs from lead poisoning, and tering at the refuge, for they began to die that these outbreaks represent a cross sec- from lead poisoning as soon as the feed- tion of such conditions in the United ing areas became restricted by ice. States. Today there are only a few places Thirteen trumpeter swans affected by in this country where 1,000 or more ducks lead poisoning were found by Dr. Ian might succumb from lead poisoning and McT. Cowan (Tener 1948:12) in Feb- not be noticed. Past experience shows ruary of 1943 on Vancouver Island, Brit- that the public becomes alarmed when ish Columbia. However, only a very few large numbers of dead ducks are observed ducks have been found ill from lead poi- and that it reports such events to conser- soning in that province (E. W. Taylor, vation authorities or the press. letter, March 22, 1954). Moreover, waterfowl are prone to con- In regard to lead poisoning in Wash- centrate in and around refuges; refuge ington, Henry A. Hansen (letter, Febru- personnel would be among the first to be- ary 26, 1955) wrote: "It has been a rare come aware of and report any unusual and isolated case that weak or dead ducks waterfowl mortality. Since the early have been found to have lead shot in their 1930's, there have been numerous federal gizzards in this state since we organized refuges, manned with technically trained the waterfowl research project in 1947. personnel, well distributed throughout the In no instance have we found a trouble four flyways. spot that might require remedial action." In addition to the waterfowl die-o£fs Chester E. Kebbe (letter, April 21, that attract public attention, there are 1955) reported that, although an out- the scattered day-to-day losses that pass break of lead poisoning had not been no- unnoticed. These day-to-day losses are ex- ticed in Oregon, he believed that research tensive ; their magnitude is explored later would reveal large numbers of waterfowl in this paper on the basis of the incidence dying each vear from ingested shot. Rich- of ingested shot in waterfowl populations ard E. Griffith (letter, May 17, 1955) and the toxicity of various doses of lead reported that records at the Malheur Na- shot. tional Wildlife Refuge in southwestern Lead poisoning outbreaks have occurred Oregon indicated that there had been no more commonly in the Mississippi Flyway losses from this malady in the previous 7 than in all the other flyways combined. years. A few waterfowl, mostly diving In both the Mississippi and Central fly- ducks, were victims of lead poisoning at ways, mallards have been the principal that refuge in 1942. victims in all but a few die-ofFs. A rough C. Vic Oglesby (letter, March 31, estimation of the annual rate of loss of 1955) reported: "There have been no mallards in outbreaks of lead poisoning in major die-of¥s nor any approaching even the Mississippi Flyway is 1 per cent. moderate die-offs in Nevada within the Frequency of Die-OflFs past 10 years. A very few birds, primarily shovelers, fall victim to lead poisoning Some areas have outbreaks of lead poi- each fall on the Stillwater Wildlife Man- soning in waterfowl rarely, some occa- 246 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 sionally, and others with rather consistent occurred during the late fall and early frequency. For example, in Illinois there winter months, after the close of the has been but one outbreak of lead poison- hunting season. Only a very few die-ofts ing, near Henry in 18 years; near Grafton have been noted during the hunting sea- there have been two outbreaks in 12 years; son, even though in the southern zone at the Chautauqua National Wildlife the season has usually extended to Janu- Refuge there have been outbreaks in 10 ary 10 or 15. Two large outbreaks have of the last 13 years. been reported during the hunting season: The frequency and magnitude of lead One of these occurred at Catahoula Lake, poisoning outbreaks in a particular area are Louisiana, during the last two weeks of influenced largely by the following fac- November and the first week of Decem- tors: the size of late fall and winter popu- ber in 1950; the other took place in the lations of mallards and other species of Claypool Reservoir area of Arkansas be- ducks with similar feeding habits ; the tween mid-December of 1953 and early kind and amount of food available; the February of 1954. amount of lead shot present as a result of Outbreaks of lead poisoning are un- shooting pressure; the availability of shot, usual during the early fall months. determined by bottom conditions, water Hunter activity keeps ducks out of heavily levels, and ice cover. gunned areas where shot pellets are most One reason that the Chautauqua Na- heavily deposited, and, as shown later, a tional Wildlife Refuge area has been the sizable number of the ducks suffering scene of many outbreaks of lead poisoning from the effects of lead poisoning are shot in waterfowl is that generally 100,000 to by hunters. 400,000 mallards winter there, making it Outbreaks of lead poisoning seldom usually the area of largest winter concen- have been noted among waterfowl during tration in Illinois. Another reason is that the spring. Principal losses at this season nearby Quiver Creek, which remains have been among swans and geese. Whis- partly open during the coldest weather, at- tling swans have been recorded as dying tracts a large proportion of the wintering during the spring at Green Bay, Wiscon- population to its shot-laden stream bed. sin, and on the Shiawassee National Wild- Water levels, food, and a lack of ice life Refuge, Michigan, table 1. A die-olif cover combined to cause the exceptionally of Canada geese took place in April, 1954, large die-off of 5,000 mallards in the at Lake Puckaway, Wisconsin. In Nebras- Chautauqua area during the winter of ka, losses of blue geese and snow geese 1956-57. A rise in water resulted in the have occurred for a number of years dur- flooding of millet and smartweed beds ing March and April. Greater scaups adjacent to the refuge shortly after the were reported by Van Tyne (1929:103- hunting season closed. This area had been 4) as dying at Houghton Lake, Michigan, heavily shot over, and mallards congre- during April, 1928. In the spring of gated there for a week before a freeze-up 1921 near Florence, Louisiana, many forced them to leave. Most of them moved ducks died from lead poisoning, according to Quiver Creek. Two to 3 weeks later, to Albert Bonin, quoted in an unpub- mallards in the Quiver Creek area com- lished report by E. R. Kalmbach. menced dying by the hundreds. There are no records to indicate that in Other areas in the Mississippi Flj'way recent years wild waterfowl have died where there have been consistently fre- from lead poisoning during the summer quent outbreaks of lead poisoning include months. However, Wetmore (1919:2) Catahoula Lake, Louisiana, 4 out of 6 stated that during the summers of 1915 years; Claypool Reservoir, Arkansas, 3 and 1916 he handled many ducks af- out of 8 years; and Squaw Creek Na- fected by lead poisoning in the Bear River tional Wildlife Refuge, Missouri, 8 out Delta of Great Salt Lake, Utah. In spite of 13 years. of numerous and intensive investigations on botulism and other waterfowl problems Seasons of Die-OflFs at the Bear River Migratory Bird Refuge, As shown by data in table 1, most wa- lead poisoning losses have not been re- terfowl die-offs from lead poisoning have corded there during the summer since , May, 1959 Bellrose: Lead Poisoning in Waterfowl 247 Wetmore (1919) reported on his field ing. In a 3-day period, 243 mallards and work of 1915 and 1916. only 26 pintails were picked up. Not a single dead or incapacitated green-winged Species AflFected by Die-Offs teal was found. Individuals of most species of water- From these observations, it was de- fowl have been recorded at one time or duced that the habits of the several species another as victims of lead poisoning. In of ducks were such as to account for the addition to those species listed in table 1, different mortality rates. Observations of the following species have been reported tile feeding ducks plus unpublished food as victims: trumpeter swan, white-fronted habits studies of ducks at Catahoula Lake {Jtiser gadwall goose albifrons) , {Anas by Richard K. Yancey of the Louisiana strepera) , baldpate {Mareca americana) Wild Life and Fisheries Commission sug- blue-winged teal {Anas discors) , cinna- gested that both feeding traits and food mon teal {Anas cyanoptera) , shoveler preferences were involved. Ducks of all {Spatula clypeata), canvasback, greater three species, mallard, pintail, and green- scaup, common goldeneye {Bucephala winged teal, were feeding extensively in clangula) , and ruddy duck {Oxyura ja- flooded beds of chufa {Cyperus escnlen- maicensis) . The largest number of spe- tus), but mallards were puddling more cies reported from any one area was found commonly into the bottom for tubers of by Donald D. McLean (unpublished re- this plant than were pintails, which were port, California Department of Fish and probably feeding more commonly on the Game) in the San Francisco and Suisun floating seeds. Green-winged teals ap- Bay areas of California. He reported 257 peared to be feeding almost entirely on pintails, 45 shovelers, 15 baldpates, 13 floating seeds. green-winged teals {Anas carolinensis) Apparently, in puddling into the bot- 7 mallards, 2 lesser Canada geese, 1 cin- tom mud, mallards came into contact with namon teal, and 1 canvasback in a group the lead shot more frequently than did of waterfowl which had succumbed from pintails, and pintails more frequently than lead poisoning. did green-winged teals. The form of the Although individuals of many species food they consumed undoubtedly influ- have died from lead poisoning, it is evi- enced mortality among those ducks ingest- dent that the mallard has been the prin- ing shot. Jordan & Bellrose (1951:18) cipal victim in outbreaks of lead poison- reported that ducks that fed on small ing across the nation, table 1. In the Pa- seeds were less affected by ingested lead cific Flyway the pintail has made up the than were those that fed on corn. The largest number of victims. In the Missis- tubers of chufa and the kernels of corn sippi Flj'way, however, where mallards appear to have similar physical proper- and pintails have frequented the same ties and they may be expected to have areas, mallard losses have been propor- similar effects. tionately greater, table 1. Die-offs of Incidence of Lead Shot in Die-Offs the Canada goose, blue goose, and snow goose have been reported for several Biologists investigating outbreaks of places, table 1, but losses in these die-offs lead poisoning among waterfowl in the have been comparatively small. Mississippi Flyway, 1938-1955, exam- An investigation of a lead poisoning ined samples of dead and dying mallards outbreak at L atahoula Lake, Louisiana, for ingested shot, tables 2 and 3. Al- in January of 1953 pointed up important though 10.4 per cent of the drakes, table differences in the mortality rates of spe- 2, and 13.0 per cent of the hens, table 3, cies. During the period of the outbreak, found in the outbreaks carried no shot in the waterfowl population was composed their gizzards, most, if not all, of these of 30,000 pintails, 25,000 mallards, 5,000 were lead-poisoned victims. James S. green-winged teals, and small numbers Jordan (unpublished report) found in of a few other species. Although pintails controlled experiments with captive mal- outnumbered mallards in the population, lards that 21 per cent of those dosed with 5,500 mallards and 1,000 pintails were one to four No. 6 shot pellets had no pel- estimated to have died from lead poison- lets in their gizzards at time of dearh. 248 Illinois Natural History Survey Bulletin Vol. 27, Art. ^ Table 2.—Incidence of various ingested shot levels found among drake mallards picked up level is meant the number of ingested lead shot pellets found in a gizzard.) For each state are Mav, 1959 Bellrose: Lead Poisoning in Waterfowl 249 in a dead or moribund condition in lead poisoning die-offs in six states, 1938-1955. (By shot given the number and per cent of drakes represented at each shot level. 6 Pellets 250 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 bagged is five; if every shell were of 12 Because of the scattered distribution of gauge and contained No. 6 shot, then blinds, many acres of waterfowl habitat about 1,400 shot pellets would be depos- are untouched by spent shot, while small ited for every duck bagged. areas near blinds have an annual deposi- In Illinois, the annual kill at some pub- tion of shot many times as great as the lic shooting grounds has been as high as calculated average for the larger acreage six ducks per acre, but for all Illinois of which they are a part. Most blinds are duck hunting areas over a period of years located on or adjacent to the best water- the kill has averaged about one and one- fowl feeding grounds. In such situations, half ducks per acre per year. The amount waterfowl are more likely to pick up shot of lead shot deposited in Illinois River in their feeding activities than if the valley lakes is calculated to be approxi- blinds, and therefore the pellets, were mately 2,100 pellets per acre per year. more evenly distributed. LU O cr UJ CL NUMBER OF SHOT PELLETS Fig. 3.— Incidence of various levels of ingested lead shot found in gizzards of drake mallards picked up in a dead or moribund condition in each of four areas in which lead poisoning die-offs occurred, 1941-1954. Data, except those for Illinois, are from table 2. .. May, 1959 Bellrose: Lead Poisoning in Waterfowl 251 A number of surveys have been made 13 pellets at each sampling point; most of lake and marsh bottoms in an effort to of the pellets had penetrated through 10 ascertain the availability of lead shot to to 12 inches of a soft upper layer of mud waterfowl. Wetmore (1919:9-10), in to a lower layer of hardened clay. his pioneering investigation of lead poi- More recent studies, table 4, show the soning, examined mud from two areas at concentrations of lead pellets in bottom the mouth of the Bear River in Utah, in samples, most of them taken without spe- one area he found no shot pellets within cific orientation to shooting blinds. The 30 to 70 yards of a blind, but he found bottom material sampled varied in thick- pellets at sampled 20-yard intervals from ness from 2 to 10 inches. 70 yards to as far as 210 yards from the The greatest concentration of lead shot shooting point. He found most pellets at that has been reported was at Lake Puck- a distance of 130 yards, where he recov- away, Wisconsin, table 4. Hartmeister Si ered 1 to 12 in each sieve filled with mud. Hansen (1949:18-22), after investigat- In the other area, Wetmore found 1 to ing three Wisconsin shooting areas, re- Table 4.—Number of lead shot pellets per square foot and per acre found in samples of the bottom soils of various lakes and marshes used extensively by waterfowl in North America. The bottom samples varied from approximately one-half inch to 10 inches in thickness.* State Area California. Sacramento Valley 1939, 1940 North Bay, San Francisco. Springs Suisun Bay Delta . South Bay, San Francisco San Joaquin Valley South Coast Minnesota. Lakes on Carlos Avery 1939-1940 Refuge Winter Lakes adjacent to Carlos Avery Refuge Rice Lake Rush Lake Heron Lake 24 Lakes Wisconsin. Lake Puckaway. Clam Lake Horicon Marsh. Manitoba. Portage Creek, Delta Marsh Cadham Point, Delta Marsh Michigan. Saginaw Bay Maumee Bay Indiana. . . Willow Slough Illinois. Quiver Lake Moscow Bay 252 Illinois Natural History Survey Bulletin Vol. 27. Art. ^ ported 2.71 pellets per square foot (equiv- lowest layer. There was a noticeable dif- alent to 118,048 pellets per acre) at Lake ference between places; areas with hard Puckaway, less than half as many pellets bottoms had most of the shot pellets at per square foot at Clam Lake, and a "neg- depths of less than 6 inches while areas ligible amount of lead shot available to with soft bottoms had a greater propor- waterfowl" on Horicon Marsh. Lake tion of shot deeper in the soil. McLean Puckaway, they reported, has a bottom of reported that at the Bolsa Chica Club, in sand and gravel covered by a thin layer southern California, there was a heavy of vegetable matter 1 to 6 inches in depth. concentration of shot lying on hardpan Clam Lake has a similar bottom. The dif- under 5.5 inches of soft mud. ference between the areas in number of Both Portage Creek and Cadham Point pellets per square foot may reflect differ- in the Delta Marsh of Manitoba are tra- ences in hunting pressure. ditional shooting sites. Portage Creek re- Hartmeister & Hansen (1949:19) con- ceives much heavier shooting pressure cluded: "Sampling on Horicon marsh re- than does Cadham Point, and shot pellets vealed a practically negligible amount of were more numerous there, table 4. In lead shot available to waterfowl, in spite view of the soft mud bottoms of both of the fact that this area is probably as areas, the amount of shot found was sur- heavily hunted as any lake or marsh in prisingly high. George K. Brakhage the state of Wisconsin. Obviously, lead stated in an unpublished report cited in a shot are soon made unavailable to water- table 4 footnote that the highest concen- fowl where deep layers of muck and peat trations of shot in the Cadham Point area are present." were along those transects nearest the de- Bottom samples were taken at the Car- coy placement. In Michigan, Herbert J. los Avery Refuge in Minnesota 5 years Miller stated in an unpublished report after it had been closed to shooting; yet cited in a table 4 footnote that at Mau- shot pellets were about as numerous there mee Bay shot pellets were twice as nu- as in adjacent lakes that were hunted dur- merous in areas protected from severe ing the 5-year period (unpublished Min- wave action as in the exposed areas. Part nesota report cited in table 4 footnote). of this difference may have resulted from At Rush Lake, a mud-bottomed water differences in shooting pressure, but Miller area, no lead shot was found in samples believed that the wave action and cur- taken 15 years after it had been closed to rents were largely responsible in that they hunting. The highest concentration of covered much of the lead with sediment. lead shot found in the Minnesota lakes Bottom samples taken during the sum- sampled was at Heron Lake, which has mer of 1950 from two heavily shot-over a hard clay bottom and had been heavily lakes in the Illinois River valley showed shot over, table 4. few lead shot pellets, table 4 ; samples Bottom samples taken at Willow were taken from the top 2 inches of the Slough in Indiana by Dale N. Martin bottoms of these lakes. Undoubtedly only (1957:113) revealed about the same con- a small amount of lead shot was found centration of lead shot pellets on October because the expended shot sank in the 17, 1956, as on April 26, 1956, table 4. soft mud and during spring floods was Apparently, during the 6-month period covered by a laj^er of silt. A study on the the shot had not settled deeper into the silting of Lake Chautauqua (Stall & Mel- bottom. The bottom area sampled was sted 1951:10), an Illinois River valley composed of one-half to 1.5 inches of silt lake, showed an average annual silt accu- and plant debris over firm sand. mulation of no acre-feet in a basin of In California waterfowl areas, Donald 3,562 acres. D. McLean (unpublished report cited in In water areas with silt or peat bot- J table 4 footnote) took bottom samples at toms, there is, apparently, only a slight i levels of 0-2 inches, 4-6 inches, and 8-10 carry-over of lead shot (within the soil inches below the surface of the bottom. depths at which most ducks search for At these three levels he found 61 per cent food) from one season to the next. Lead of the shot in the top layer, 30 per cent shot is, therefore, most readily available in the middle layer, and 9 per cent in the to waterfowl in the fall and winter, dur- May, 1959 Bellrose: Lead Poisoning in Waterfowl 253 ing and immediately following the hunt- The data in table 5 show that the ing season. High water levels during the smaller the shot size, the smaller the spring over much of the fall waterfowl amount of recovered lead. Evidently wave habitat, which includes most shooting action dislodged quantities of shot pel- grounds, greatly diminish the availabil- lets, especially 7i/2's, and scattered them ity of lead shot. Most breeding grounds outside the pipes. From the distribution are lightly hunted ; therefore, waterfowl of the remaining pellets, there was, with are only slightly exposed to lead shot dur- the exception of 7'/2's on the moderately ing the breeding season. firm bottom, evidence that the larger the As part of a study on lead shot in mud- size, the more prone the pellets were to bottomed lakes, an experiment was con- sink in the bottom soil. In the soft bot- ducted by the writer at Quiver Lake, in tom soil, most of the shot had settled to Table 5.—Data indicating the penetration of lead shot pellets into bottom soil of two different types at Quiver Lake, near Havana, Illinois. Figures show for each of five pipes, 8 inches in diameter, placed with upper mouth flush with lake bottom, the number of grams of shot pellets recovered at various soil depths, September 3, 1953, and the percentage of the recovered shot that was recovered at each depth. At the upper mouth of each pipe, 150 grams of shot pellets. No. 7'/2 or No. 6, had been deposited on August 13, 1952. 254 Illinois Natlral History Survey Bulletin Vol. 27, Art. 3 deep, but, in deeper water, they are prone is influenced by the feeding habits of the to puddle out pockets several inches in birds and by the kinds of foods available, depth. Mallards, in Illinois at least, dig as well as by the numbers of shot pellets deeper pockets than do pintails, but these available. are seldom more than 6 inches in depth. According to W^etmore (1919:3), mal- INGESTED LEAD SHOT IN lards and pintails dig away mud to a depth MIGRATING DUCKS of 6 to 18 inches and over an area 1 to 15 feet in diameter as they search for food. The incidence of ingested lead shot in Such extensive digging on the part of migrating waterfowl populations (the ducks has been observed by the present percentages of ducks that carried ingested writer only around trap sites where large lead at the time gizzards were collected) numbers of birds have sifted through bot- was determined by ( 1 ) fluoroscopic ex- tom soil day after day for bait. Under amination of live-trapped ducks, (2) com- such circumstances, mallards have created pilation of data obtained from other in- holes as large as 2 feet in depth, 25 feet vestigators who had examined waterfowl in length, and 10 feet in width. gizzards for food content, and (3) fluoro- Field observations and food habits stud- scopic and direct examination (Bellrose ies indicate that, where underwater leafy 1951 : 126-7 ) of gizzards numbering many aquatics occur, baldpates and gadwalls thousands that co-operating biologists had feed almost entirely upon these plants, collected, especially for this study, from seldom, if ever, sifting through bottom ducks in hunters' bags. Most of the data soils for food. were from ducks migrating southward in Not only does the depth at which lead fall and early winter. shot occurs in bottom soils determine its Shot in Live-Trapped Ducks availability to different species of ducks; the depth of water above the bottom is During the fall months of 1948, 1949, also a factor. Species of ducks differ to 1950, and 1953, 5,148 mallards were live- some extent in preferred feeding depths. trapped and fluoroscoped at the Chautau- Dabbling ducks usually utilize waters less qua National Wildlife Refuge, near Ha- than 15 inches in depth, and diving ducks vana, Illinois, fig. 4. Ingested lead shot feed at depths of many feet. Among the was found in the gizzards of 10.14 per diving ducks, redheads {Aythya atneri- cent of these birds, but more than two- cana) and ring-necked ducks {Aythya thirds of the gizzards with shot contained collaris) are prone to feed in shallower only one pellet each, table 6. Because the water than are lesser scaups and golden- refuge has been closed to hunting since eyes. 1944, it is doubtful if much, or any, of the When, in late fall or winter, ice fails to lead was picked up at the trapping site. cover waterfowl feeding grounds that Almost twice as many juvenile as adult have been heavily shot over, the stage may male mallards carried ingested shot, table be set for a large die-off of ducks. Ice 6. The data indicate that more hens than almost invariably forms first on the shoal drakes carried ingested shot, but the sam- water of ponds, marshes, and lake mar- ple on which the data are based is believed gins such as are commonly used by ducks biased by an unduly large proportion of for feeding and hunters for shooting. The hens fluoroscoped late in the season, when sealing of these waters by ice makes the the incidence of birds carrying shot was large quantities of shot on such areas un- at its highest. available to waterfowl. At the same time Pintails, blue-winged teals, and wood it may cause the ducks to congregate in ducks {Aix sponsa) were caught in baited spring holes and spring-fed streams not traps during September at Moscow Bay, covered by ice. If such areas have been 10 miles south of Havana. Examination heavily hunted, they are potential sources of these birds by fluoroscopy revealed an of large die-offs caused by lead poisoning. incidence of ingested lead that was un- The extent to which the various spe- usually high for these species, table 7. cies of waterfowl are exposed to shot pel- The high incidence may have occurred be- lets on the bottoms of marshes and lakes cause the traps were on a heavily shot- May, 1959 Bellrose: Lead Poisoning in Waterfowl 255 over area, which, combined with intensive In two of the three species, table 7, an feeding by the ducks, resulted in exposure appreciably greater percentage of juveniles of the birds to unusually large quantities than of adults carried ingested lead shot; of lead. in the pintail there was little difference in At the trapping site, lead shot was avail- shot incidence between age groups. In able equally to the three species, and, in the pintail, blue-winged teal, and wood September, it was unlikely that the birds duck, there were only slight dififerences were obtaining shot elsewhere. Yet, between the sexes with respect to inci- among the species, there were differences dence of shot, but, in the lesser scaup, pro- in incidence of ingested shot, table 7. Pro- portionally twice as many drakes as hens portionally more pintails than wood ducks carried ingested shot, table 7. The lesser and proportionally more woodies than scaups represented in table 7 were trapped blue-winged teals carried ingested shot. on another area near Havana in April, Apparently, there is a relationship between 1953. the weight of a duck and its intake of food The seasonal incidence of ingested lead and lead. Perhaps under similar condi- shot among mallards trapped at the Chau- tions of food and feeding, the duck spe- tauqua National Wildlife Refuge during cies with the largest individuals have the the fall months of 1949 and 1950 is shown highest percentages of individuals with in- in table 8. Most of the mallard groups gested lead shot, table 7. fluoroscoped early in the season had a Fig. 4.—An X-ray head and fluoroscopic screen used at the Havana laboratory of the Illinois Natural History Survey to determine the incidence of ingested lead shot in wild water- fowl trapped alive as well as in dead and moribund birds picked up in the field. Each bird was placed in the cone, which was rotated in front of the fluoroscopic screen. This procedure presented to view more than one plane of the bird's body and thereby resulted in more precise location of pellets than was possible in a single plane view. (Photograph from the Journal-Star, Peoria, Illinois.) 256 Illinois Natural History Survhy Bulletin Vol. 27, Art. ?, G It; o ^JS •- o Saw•o > a— *j I S-a V * « « w c « Qi S «> o V o *"e w o 22 w o *' 3 « <« « C "^ C St3 « B '° 1-1 «- s. £•— O a > to c 3 5 o A »• O JD "wS 1 <« « — <_, i '"So V B Si «* i: .S — 3 ,2 o w U > •on CB SI'Sb*j: C8 O HE'S May, 1959 Bellrose: Lead Poisoning in Waterfowl 257 lower percentage of individuals with in- no ingested shot. Examination of winter- gested shot than had groups fluoroscoped ing ducks (most of them black ducks, can- later in the season. The decline in the in- vasbacks, lesser scaups, and redheads) by cidence of ingested shot among birds Hunt & Ewing ( 1953 :362) along the De- fluoroscoped in the December 20—24 pe- troit River disclosed that less than 4 per riod may have occurred as a result of the cent of 7,700 ducks fluoroscoped had lead freeze-up of the lakes a week or two be- in their gizzards. fore, or as a result of a rapid die-of^ of Of more than 1,000 ducks, most of lead-poisoned birds in a period of cold them black ducks, that were fluoroscoped weather. during the fall, winter, and spring months Erratic changes in incidence of ingested in New York, only a very small propor- shot from period to period were evidence tion carried ingested lead, table 10. Only of population changes brought about by a small proportion of mallards trapped the arrival and departure of migrating during the winter months in South Da- mallards that varied greatly from flight kota had lead in their gizzards. to flight in the amounts of ingested lead Of six species of ducks fluoroscoped they carried. during the summer months in the Great A few waterfowl in Illinois have been Salt Lake Basin of Utah, the mallard was fluoroscoped in late winter or spring for the only species in which a moderately evidence of ingested lead shot. Ingested large proportion of individuals carried in- shot was found in a moderate percentage gested lead, table 10. of the lesser scaups examined, table 7, It An astoundingly large proportion of the was found in a very small percentage of mallards, pintails, and redheads, and a the birds in one group of pintails; it was smaller proportion of the blue-winged not found in another group of pintails nor teals fluoroscoped during the summer at in a sample of Canada geese, table 9. Delta Marsh, Manitoba, carried ingested Many ducks in other states have been lead shot, table 10. All of the redheads and fluoroscoped for evidence of ingested lead most of the blue-winged teals and pin- shot, table 10. In Michigan, small per- tails were juveniles. The findings of centages of mallards and black ducks Elder (1950:501) agree with Illinois {Anas rubripes) were found to carry in- data in indicating that juvenile ducks are gested lead during the winter and spring more likely to ingest lead shot than are months. Lesser scaups that were fluoro- adults ; at Delta, over twice as large a scoped during the spring months contained percentage of juveniles as of adult mal- Table 8.—Periodic incidence of ingested lead shot among mallards trapped at the Chautauqua National Wildlife Refuge near Havana, Illinois, during the fall months of 1949 and 1950. Period — 258 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 lards were found with lead in their giz- gested shot among waterfowl. The Delta zards, and over three times as large a per- ALirsh, which is one of the most heavily centage of juvenile as of adult pintails shot-over areas in Canada, is an excep- carried ingested lead. tion. On other breeding ground areas Shot in Ducks Bagged by Hunters Whitewater Lake, Manitoba, and Eye- brow Lake, Saskatchew^in—Elder (1950: With the help of wildlife biologists in 501) examined 3,300 ducks during the almost every state of the Union and some .summer months of 1948 and 1949 and Canadian provinces, the Illinois Natural found that less than 1 per cent of the in- History Survey obtained data on the in- dividuals of any species carried ingested gested lead shot found in the gizzards of lead. Undoubtedly, most breeding ground more than 40,000 waterfowl bagged by areas would show a low incidence of in- hunters in the autumn and earlv winter Table 9.—Incidence of ingested lead among pintails and Canada geese trapped and fluoro- scoped in Union County and pintails trapped and fluoroscoped in Henderson County, Illinois, 1952 and 1953. Species , May, 1959 Bellrose: Lead Poisoning in Waterfowl 259 Fig. 5.— Shot pellets from the gizzards of wild ducks bagged by hunters. Pellets A and B were from the same gizzard. Pellet A entered the gizzard lumen from the charge that killed the bird. Pellet B had been ingested previously. Pellet A exhibits craters caused by the strik- ing of this pellet against others in passage through the shotgun barrel. Pellet B has been some- what smoothed by abrasion in the gizzard ; under magnification, the surface of this pellet shows pitting and flaking. Pellet C, another ingested pellet from another gizzard, shows surface erosion resulting from the action of digestive juices in the gizzard. months of the period 1938-1953. Lead long to the genus Aythya, there is no re- pellets, two ingested and one not ingested, lationship between the incidence of shot are shown somewhat magnified in fig. 5. and the phylogeny of the birds. The number of shot pellets and the spe- Shillinger & Cottam (1937:402) be- cies of ducks represented were known for lieved that ingestion of lead shot was re- each of 36,145 gizzards; data from these lated to the availability, or lack of availa- gizzards were used in an analysis of the bility, of grit, for they stated : "While lead incidence of shot among each of the prin- poisoning is widely distributed throughout cipal kinds of waterfowl of North Amer- all sections of this country, evidence ica, table 11. seems to indicate that it is more severe in Variations in Shot Incidence those sections where there is a deficiency Among Species.—The incidence of of available gravel that may serve as grit ingested lead shot was about seven times in the gizzard of the birds." as great among ducks as among geese, ta- Tener (1948:38) believed grit prefer- ble 11. Less than 1 per cent of the (\an- ences to be a factor influencing shot inges- ada geese and less than 3 per cent of the tion by waterfowl. He noted that only blues and snows were found to have lead fine sand appeared in baldpate and green- in their gizzards; the numbers of shot pel- winged teal gizzards, and that a large lets per gizzard were exceedingly low. proportion of the gizzards of these species There was a wide range in incidence contained no shot. He speculated that of ingested shot among the different kinds lead pellets were too large to be selected of ducks, table 11. Kinds in which less as grit by these species. than 2 per cent of the gizzards contained If waterfowl were prone to pick up lead lead were bufflehead {Bucephala albeola) shot for grit, then it would seem reason- green-winged teal, mergansers {Mergus able to expect many species which pick up spp.), wood duck, shoveler, and gadwall. large-sized grit particles to have ingested Kinds in which lead was found in more more shot pellets than the numbers re- than 2 and less than 5 per cent of the giz- corded for them in table 11. Ducks that zards were blue-winged teal, baldpate, commonly pick up grit particles that are and common goldeneye ; in more than larger than a No. 6 shot and that show a 5 and less than 10 per cent, ruddy duck, low incidence of shot are wood duck, buf- mallard, black duck, and pintail ; in more flehead, and common goldeneye. The giz- than 10 per cent, canvasback, lesser scaup, zards of geese contain quantities of large redhead, and ring-necked duck. grit particles, but the incidence of shot It is apparent that, with the exception among geese is lower than among ducks, of the last-named group, all of which be- table 11. 260 Ii.MNOis Natural History Survey Bulletin Vol. 27, Art. 3 oo ^ ;^ vo r^ O O vC .— -H "^ \C OO 1 CO OO CN — co-^ — coroO — o c 04 'U d vnoor^irioc^-^ts 'U OOOO — OOOO^—'fO-^COOO ocs; iOoo--TfTt ooooooooooooooooo E *- o^<~^oo--oooO'- 'U oooooooooocoooooo --I f^ ^ ^ ^ O (N ^ O — O —< O O — O O O 'U OOOOOOOOOOOrOOOOOO — -O -< O OS --1 O '-' O O (N Tf CO O O O O Oo o o o o ooocoooooo-^o-^oooo o o o o "C « O lo c) --H r^ -^ iOO-<* Oh u ^^OO—'OOOO'-'^—-rlOOOO 'U Tfto-—(Ol«^ — -H^H^HO^O^oor---HO-^fO ^- CN oo ro 'sh -- fo r-^ — "^ 0(N— iOU-lfNTfTj May, 1959 Bellrose: Lead Poisoning in Waterfowl 261 Evidence that the size of grit usually them need not sift bottom material, as do ingested by individuals of a species of those feeding upon the tubers, rootstocks, water bird is not related to the ingestion and seeds of aquatic plants. of shot by individuals of that species is ap- Mallards (6.79) and pintails (8.87) parent from a study of the stomach con- do considerable feeding in grainfields, tents of 792 coots {Fulica americana) which may somewhat reduce their expo- Lead shot was found by Jones ( 1940 : 11 sure to deposited lead shot. However, in only 12, or 1.5 per cent, of 792 stom- when feeding in lakes and marshes, they achs. Gravel was found in all but 7 of the are, for the most part, active in heavily 792 stomachs and averaged 33 per cent shot-over areas. Moreover, their habit of of the gross contents. The low incidence puddling deep into the bottom soil for of shot in the stomachs was attributed by seeds exposes them to deposited lead more Jones to the habit that the coots have of frequently than other dabbling species, ex- dabbling for food on the surface of the cepting the black duck, which behaves sim- water as well as to their inability to sift ilarly. through bottom material with their Redheads (13.57), ring-necked ducks chicken-like bills. Yet it is reasonable to (14.18), canvasbacks (11.84), and lesser assume that they could pick up shot pel- scaups (13.09) normally dive for food in lets with their bills as readily as they comparatively shallow water in their could pick up grit particles. search for seeds, tubers, and rootstocks of Food preferences and feeding habits of aquatic plants. Plant items, according to the various species of waterfowl appear Cottam (1939:53), make up 60 to 90 to be largely responsible for the differ- per cent of the food of these ducks. The ences in the incidence of ingested shot combined effect of feeding in heavily shot- among the species. The following discus- over waters and the types of food taken sion of feeding habits tends to support result in a higher frequency of ingested this thesis. Figures in parentheses fol- shot pellets in this group of diving ducks lowing the name of a kind of waterfowl than in any other group or species of wa- indicate the percentage of gizzards in terfowl. which shot pellets were found, as pre- Regional Variations in Shot Inci- sented in table 11. dence.—The incidence of ingested lead Shovelers (1.60) and green-winged shot among ducks of 1 1 important species teals (1.36) feed on the surfaces of mud was determined for each of the North flats and marsh bottoms. Gadwalls (1.84) American flyways by examination of 39,- and baldpates (3.17) feed upon the veg- 610 gizzards collected in the fall and etative parts of aquatic plants and seldom early winter months of 1938—1954, table have occasion to dig into the bottom soil 12.' where shot pellets are present. The incidence of ingested lead was Wood ducks (1.58) feed so extensively lowest in ducks of the Central Flyway. on fruits of woodland plants (Martin, There were only small differences be- Zim, & Nelson 1951:65) that they sel- tween the figures for North Dakota, dom puddle or sift through lake and South Dakota, Nebraska, and Colorado; marsh bottoms for food. Mergansers for Texas the incidence of shot was sev- (1.46) feed principally on fish and there- eral times as high as that for any other fore have less occasion to ingest shot than state in the fly way. In the Dakotas, only have species which search through bottom the shoveler, redhead, and canvasback materials for food. showed an appreciable incidence of in- Common goldeneyes (3.52) and buf- gested lead, whereas in Texas most spe- fleheads (0.69) are prone to frequent cies showed a high incidence of such lead. large, open bodies of water, over which The incidence of ingested shot pellets there is little shooting, and more than 70 was about twice as high among ducks of per cent of their food is made up of ani- the Atlantic Flyway as among those of mal life, especially crustaceans and insect the Central Flyway, table 12. The inci- larvae (Cottam 1939:132). These ani- dence figures were higher for Massachu- mal organisms are found at or near the setts, North Carolina, and South Carolina surface of the bottom; ducks feeding upon and Georgia than for Maine, New York, 262 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 a group of other Atlantic states, and Flor- were from the interior areas of those ida. With few exceptions, waterfowl giz- states. Species in the Atlantic Flyway zards from the above states came from with the highest incidence of ingested lead areas near or on the Atlantic Coast; most shot were the pintail, canvasback, and samples from New York and Florida redhead. Next in order were the mallard Table 12.—Regional incidence of ingested lead shot among ducks of 11 important species; the United States and Canada, 1938-1954. May, 1959 Bellrose: Lead Poisoning in Waterfowl 263 and the lesser scaup, the black duck, and lantic FIy\va\-, table 12. Ducks near Van- the ring-necked duck. couver, British Columbia, showed a higher The incidence of ingested shot among incidence of ingested shot than did those ducks of the Pacific Flyway was only in any other area of the fl\TV'ay. In con- slightly higher than that found in the At- trast, ducks in adjacent Washington data are from 39,610 gizzards collected during fall and early winter months from hunters in Green- Winced Teal 264 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 Table 13.—Incidence of ingested lead shot among ducks of 10 species at Hovey Lake, near Mount Vernon, Indiana; the data are from gizzards collected in the waterfowl hunting seasons of 1949, 1950, and 1951. May, 1959 Bellrose: Lead Poisoning in Waterfowl 265 higher among ducks of the Mississippi ducks. Since that time, duck hunting at Flyway than among those of any other Hovey Lake has been restricted to blinds. flyway, table 12. The highest incidence Jump shooters, in wading the brush-cov- figure for the Mississippi Flyway was for ered shore of Hovey Lake, hunted a zone ducks taken in Indiana; these figures were in which ducks suffering from lead poi- not typical for the state, as the bulk of the soning were prone to concentrate. Be- samples on which they were based were cause the sick ducks had difficulty in fly- from Hovey Lake, near Mount Vernon. ing, hunters bagged unusually large num- Hovey Lake is noted for lead poisoning bers of them. losses in waterfowl. A reduction in the incidence of ingested The incidence of ingested shot was lead occurred in the mallard in 1951 at high among the ducks of Louisiana and Hovey Lake, evidently because high wa- Minnesota; moderately high for those of ter, which raised the lake level during the Illinois, Tennessee, and Arkansas; and latter part of the hunting season, made quite low for those of Missouri. lead shot less easily available to this duck. The gizzard collections from Minne- The increased depth failed to reduce the sota, Illinois, and Missouri constituted ingestion of shot by diving ducks. representative samples for those states. In A comparison of the incidence of in- Tennessee, almost all the data were from gested shot in ducks taken along the Illi- Reelfoot Lake. In Arkansas, the giz- nois River with those taken along the zards were from ducks shot at clubs with- Mississippi River in Illinois, table 14, in a 35-mile radius of Stuttgart. Both disclosed a marked difference between the Reelfoot Lake and the Stuttgart area two areas. The figure for the Illinois provide a large share of the duck hunting River is more than twice that for the Mis- in their respective states. Material from sissippi. The differences in shot incidence Louisiana was largely from Catahoula between the two areas were especially Lake and the Delta region of the Mis- marked in the mallard, canvasback, and sissippi River. lesser scaup, the only species that were In the Mississippi Flyway, the inci- represented by adequate samples in both dence figure for lead shot was higher in areas. the black duck than in any other species, The Mississippi River normally car- but the data were biased by the large ries a much heavier load of sediment than number of black duck gizzards taken at does the Illinois River. Data presented by Hovey Lake, Indiana, where the inci- Suter (1948, plate 1) for the period dence of lead was extremely high. It was 1935-1945 showed that the Illinois River very high in the ring-necked duck, lesser at Peoria carried an average of 100 p. p.m. scaup, and redhead ; it was moderately for 300 days per year, whereas the Missis- high in the pintail, mallard, and canvas- sippi River at Quincy carried an average back ; it was low in the shoveler, green- of almost 300 p. p.m. for the same number winged teal, gadwall, and baldpate. of days. Apparently lead shot is covered The variation in the proportion of more quickly in the Mississippi, with its ducks with shot in their gizzards at Hovey heavier load of sediment, than in the Illi- Lake was very pronounced over a 3-year nois. period, table 13. In 1949, the highest in- Periodic Variations in Shot Inci- cidence of ingested shot found anywhere dence.—The incidence of ingested lead in the United States was recorded at shot in mallard populations migrating Hovey Lake, but in 1950 and 1951 the through the Illinois River valley in au- figure for the area was close to the aver- tumn was determined for weekly periods age for the Mississippi Flyway. by examination of 2,499 gizzards collected The extremely high incidence figures from hunters in 1938-1940, table 15. for Hovey Lake in 1949 were probably As in the case of mallards which were influenced by the hunters' kill of a large live-trapped and fluoroscoped, table 8, the number of ducks afifected by lead poison- percentage of hunter-killed birds that car- ing. Up to the end of the 1949 hunting ried ingested shot was lower early in the season, the Indiana Department of Con- season than late; up to mid-November, servation permitted hunters to jump-shoot 5.7 per cent of the gizzards examined con- 266 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 tained shot, while after mid-November 7.8 per cent contained shot. The incidence of shot among hunter- killed birds, table 15, varied from week Table 15.— Periodic incidence of ingested lead shot among mallards in Illinois; the data are from 2,499 gizzards collected from water- fowl hunters in the Illinois River valley, 1938- 1940.* May, 1959 Bellrose: Lead Poisoning in Waterfowl 267 lected in the period 1938-1953. The duck from 3.29 to 14.18, and canvasback comparison is limited to six species of from 9.77 to 11.84. ducks—mallard, pintail, redhead, ring- Shillinger & Cottam (1937:401) re- necked duck, canvasback, and lesser scaup ported lead in 39.42 per cent of the lesser —which are listed in both periods. scaup gizzards, but over one-third of In five of the six species (the exception, their sample was from the vicinity of Mar- lesser scaup), the incidence of ingested quette, Wisconsin, where shot was found shot recorded for the 1938-1953 period, in 76.5 per cent of the gizzards. The table 11, was much higher than that for large sample from an atypical area mate- the earlier period. The per cent of giz- rially biased the results. zards containing shot increased for the The incidence of ingested lead among five species as follows: mallard from mallards in the Illinois River valley dur- 2.41 to 6.79, pintail from 1.14 to 8.87, ing two different periods— 1938-1940 and redhead from 3.14 to 13.57, ring-necked 1948-1950— is shown in table 17. In a Table 18.—Incidence of various ingested shot levels found among ducks of seven species; data are from 2,184 duck gizzards (each of which contained ingested lead) collected during the fall and early winter months from hunters in North America, 1938-195^. (By shot level is meant the number of ingested shot pellets found in a gizzard.) For each species are given the number and per cent of ducks represented at each shot level. 268 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 decade, the incidence figure for Illinois 64.7 per cent contained one pellet each, mallards almost doubled. table 18; 14.9 per cent contained two Increases in the percentage of water- pellets each. Only 7.4 per cent of the fowl ingesting lead have paralleled in- gizzards containing shot pellets contained creases in the number of waterfowl hunt- more than six pellets each. ers. Because there is expectation that the Comparatively few ducks killed by number of duck hunters will continue to North American hunters during the fall increase, it can be anticipated that lead months in the period 1938-1954 carried poisoning will become a greater hazard to 20 or more ingested shot pellets each, table waterfowl than it is at present. 19. The maximum number of pellets re- Incidence of Various Shot Levels. corded was 172, in a lesser scaup gizzard. —The incidence of various levels of in- Cottam (1939:39) reported 1 to 58 pel- gested lead shot found among ducks of lets in individual gizzards of lesser scaups seven species in North America in the shot near Marquette, Wisconsin, in April, autumn and early winter months of 1909; Shillinger & Cottam (1937:403) 1938-1954 is shown in table 18 and fig. 6. reported that 179 pellets were found in (By level of ingested lead shot, or shot the gizzard of a pintail victim of lead poi- level, is meant the number of ingested soning. shot pellets found in a gizzard.) The va- Data in table 19 indicate that pintails, rious shot levels have an important bear- ring-necked ducks, and lesser scaup ducks ing on the rate of mortality in ducks for, are more likely to have large numbers of as will be shown later, the larger the num- pellets per gizzard than are the ducks of ber of ingested shot pellets per duck, the other species. higher is the death rate, other factors be- The large numbers of shot pellets found I ing equal. in gizzards of pintails, ring-necks, and Of 2,184 duck gizzards that contained lesser scaups are probably a reflection of lead when collected from hunters in many the ability of these species to tolerate the parts of North America in 1938-1954, toxic effects of lead, as well as a reflection ^MALLARD [H BLACK DUCK ^PINTAIL H REDHEAD ' El RING-NECKED DUCK ^ CANVASBACK ^LESSER SCAUP I ii PELLET 2 PELLETS 3 PELLETS 4 PELLETS Fig. 6. — Incidence of four levels of ingested shot found in gizzards of ducks of seven species in the autumn and early winter months of 1938-1954. Data are from table 18 and represent ducks shot by hunters in many parts of North America. May, 1959 Bellrose: Lead Poisoning in Waterfowl 269 of their proclivity to pick up large num- LEAD IN WILD MALLARDS bers of pellets. For example, pintails are DOSED AND RELEASED only slightly more prone than mallards to ingest shot, table 11, but the percentage Certain effects of lead poisoning on of gizzards containing 20 or more shot mallards in the wild were determined by pellets each was almost six times as great the following experiment. In the au- in pintails as in mallards, table 19. The tumns of 1949, 1950, and 1951, several percentage of gizzards containing ingested thousand migrating mallards were trapped shot was about the same in redheads, at Lake Chautauqua. Some of these ducks ring-necked ducks, canvasbacks, and lesser were dosed with either one, two, or four scaups, table 11, but larger percentages of No. 6 shot pellets each, then banded, and Fig. 7.—Penned mallards, dosed with lead shot, feeding upon coontail, apparently one of the best vegetable foods for alleviating the effects of ingested lead. gizzards with 20 or more shot pellets each released. Other ducks trapped at the same wjere found among the ring-necked ducks time were banded and released, undosed, and scaups. to serve as controls. As shown by Jordan & Bellrose (1951 : In 1949 and 1950, the trapped mal- 18), the ability of ducks to survive lead lards were taken to the Havana field lab- poisoning is influenced by the physical oratory of the Illinois Natural History form of the food consumed. The higher Survey, where they were fluoroscoped be- survival rate of pintails than of mallards fore being banded and released. Ducks may be related to the greater numbers of known to carry ingested lead when small seeds and the paucity of corn in the trapped were not included in the experi- diet of the pintails. Lesser scaups, which ment. In 1951, when the X-ray unit was consume at least twice as much animal being repaired and could not be used for life per bird as any other ducks listed in fluoroscopy, undoubtedly some ducks car- table 19 (Cottam 1939:53), apparently rying ingested lead when trapped were c^n tolerate lead to a greater degree than released as dosed or control birds. The the ducks of other species. Thus, it ap- number of these was, of course, unknown pears that animal matter is more favora- but it was probably relatively small. l^le than vegetable matter to survival of In 1949, only adult mallard drakes ducks that have ingested lead, and that were included in the experiment. In 1950 various forms of vegetable matter differ and 1951, both adult and juvenile drakes g[reatly in their effects on birds that have and, in 1951, hens also were included in ipgested lead, fig. 7. the experiment. 270 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 In 1949, 559 mallards were dosed with cant differences between the dosed and one No. 6 shot pellet each before being the control birds. The dosed birds, some released, and 560 lead-free birds were re- of which became afflicted with lead poi- leased, undosed, to serve as controls. Of soning, had (1) a greater vulnerability to the 1,172 mallards used in the experiment hunting, (2) lower ability to migrate, and in 1950, 391 were dosed with one No. 6 (3) higher over-all mortality rates in the pellet each, 392 were dosed with two No. first year after being banded and released 6 pellets each, and 389 were released, un- (from time of banding through the fol- dosed, to serve as controls. In 1951, 2,016 lowing August). mallards were used as follows : 504 Effect of Lead on Vulnerability drakes were dosed with one No. 6 pellet to Hunting each, 504 drakes were dosed with four No. 6 pellets each, 501 hens were dosed That mallards carrying lead in their with one No. 6 pellet each, and 507 drakes gizzards were more vulnerable to hunting were undosed. than were lead-free mallards is shown in Because of the considerable cost of han- tables 20-23. In 1949, mallards dosed dling the mallards used in this experi- with one No. 6 shot pellet each were 1.84 ment, it was deemed advisable to obtain times as vulnerable to hunting as were the reports of as many band recoveries as pos- controls, table 20. In 1950, they were sible from the hunters who shot the birds. 1.19 times as vulnerable, and, in 1951, As an inducement to hunters to report they were 1.41 times as vulnerable. The bands, 759 ducks released in 1949 were year-to-year variation in vulnerability banded with U. S. Fish and Wildlife probably resulted from differences in food Service reward bands (which provided a and weather conditions. certificate and booklet for each person re- Unfortunately, the effect of two and of turning one or more bands) ; 360 were four No. 6 shot pellets for each bird was marked with standard Fish and Wildlife evaluated for only 1 year. In 1950, the Service bands. In 1950 and 1951, each kill rate of mallards dosed with two No. mallard in the experiment was banded 6 shot pellets each was 1.89 times as with a special $2.00 reward band, as well great as the kill rate among the controls, as the standard U. S. Fish and Wildlife table 20. A year later, the kill rate Service band. The ratio of reward to among mallards dosed with four shot pel- standard bands recovered was more than lets each was 2.12 times as great as the 2 to 1 (Bellrose 1955). kill rate among ducks not dosed with shot. Bands recovered from the mallards During the first 5 days after the mal- used in the experiment revealed signifi- lards in the experiment were release^!, Table 20.—Relative hunting vulnerability exhibited by wild drake mallards dosed with lead and those not dosed, as measured by the ratio between dosed and undosed birds in the per cent of the banded ducks that were recovered in the season of banding. The 3,807 drakes used in the experiment were trapped at the Chautauqua National Wildlife Refuge, near Havana, Illinois, in the hunting seasons of 1949-1951. Some of the birds were banded, dosed with one, two, or four No. 6 lead shot pellets each, and released. Others, the controls, were banded and released undosed. May, 1959 Bellrose: Lead Poisoning in Waterfowl 271 the birds treated with lead were bagged each, and that survived, the period in at about the same rate as the untreated which behavior was severely affected ap- controls, tables 21-23. During the sub- peared to be longer. The data suggest sequent 6— 10-day period, there was a pro- that most wild mallards that become af- nounced increase in the bag of treated fected by lead poisoning during the hunt- ducks, especially in those dosed with two ing season either die in the second or third or four shot pellets each. week following ingestion of shot or they In the dosed wild mallards, the inges- begin their recovery by the early part of tion of lead shot did not appear to affect the fourth week. behavior until after the first 5 days. In Penned wild mallards that were dosed the mallards that were dosed with one with lead exhibited weakness and fatigue shot pellet each, and that did not die of during the second and third weeks after lead poisoning, the behavior appeared to being dosed ; these symptoms increased in be most severely affected in the 6-15-day severity during the third and fourth weeks period after ingestion ; in mallards that (Jordan & Bellrose 1951 :5-6). The keel were dosed with two or four shot pellets bone became prominent, and often the Table 21.—Relative hunting vulnerability exhibited by wild drake mallards dosed with one No. 6 lead shot pellet each and those not dosed, as measured by band recoveries in each of SIX periods, fall and early winter, 1949-50. The data are for birds trapped, banded and released at the Chautauqua National Wildlife Refuge in the fall months of 1949; 559 of the birds were dosed and 560 were not dosed. ; 272 Ii.i.rNois Natural History Sur\hv Bui.i.ftin \nl. 27. Art. 3 Table 23.— Relative hunting vulnerability exhibited by wild drake mallards dosed with one or with four No. 6 lead shot pellets each and those not dosed, as measured by band re- coveries in each of six periods, fall and early winter, 1951-52. The data are for birds trapped, banded, and released at the Chautauqua National Wildlife Refuge in the fall months of 1951 504 were dosed with one pellet each, 504 were dosed with four pellets each, and 507 were not dosed. Davs May, 1959 Bellrose: Lead Poisoning in Waterfowl 273 dosed with two pellets each had a much associated with lead poisoning reduces the larger percentage of its recoveries fall movement of ducks. The larger the within the 50-mile zone than had the con- amount of ingested lead per bird, the trol group, table 25. In 1951, one shot greater is apt to be the reduction of move- pellet for each bird seemed to have little ment by the affected segment of the popu- effect on migration, but four pellets for lation. In areas where lead poisoning is each bird greatl}' retarded migration. Less of outbreak proportions, it is reasonable to than 5 per cent of the bands recovered conclude that the bulk of the sick birds from the mallards dosed with four pellets have picked up shot within their daily each were taken farther than 50 miles feeding radius, usually less than 50 miles. from the banding station, table 26. Conversely, it can be assumed that only a Manifestly, the weakness and fatigue small percentage of the ducks that have Table 25.—Effect of ingested lead shot on migration of mallards, as measured by distances traveled by dosed and by undosed birds before they were shot by hunters. The data are for birds trapped and released at the Chautauqua National Wildlife Refuge in the fall months of 1950; 391 of the birds were dosed with one No. 6 shot pellet each, 392 were dosed with two pellets each, and 389 were not dosed. Figures show for dosed and for undosed ducks the per cent of recovered bands (those recovered in year of banding and for which distance data are available) that were recovered at various distances from the point of banding and release. 274 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 become ill from lead poisoning have mi- 1950:8-12) as to have only a minor effect grated farther than 50 miles from where upon the mortality rates. they ingested shot. Most of the year-of-banding mortality rates for the undosed, or control, groups Effect of Lead on Year-of-Banding in the experiment were lower than even Mortality Rate the lowest of the year-of-banding mortal- The mortality rates of the dosed and ity rates for mallards reported by Bell- the undosed mallards in the year of band- rose & Chase (1950:8-12). In the Bell- ing or the first year (to end of following rose & Chase study, a correction factor August) after being banded and released was used for bandings made during the are indicated bv data in table 27. Each hunting season, and mortality rates were Table 27.—The year-of-banding mortality rates of wild, free-flying mallards undosed and of similar mallards dosed with one, two, or four No. 6 lead shot pellets each. The data are for mallards trapped, banded, and released at the Chautauqua National Wildlife Refuge near Havana, Illinois. The mortality rates were derived as explained in the section entitled "Effect of Lead on Year-of-Eanding Mortality Rate." May, 1959 Bellrose: Lead Poisoning in Waterfowl 275 the controls. Adult drake mallards dosed for the undosed hens banded and released with two shot pellets each in 1950 had a in 1939-1943. year-of-banding mortality rate that was At the Rocky Mountain Arsenal, near 43.6 per cent greater than that of drakes of Denver, Colorado, wild mallards were the same age class used as controls in the banded, dosed with lead shot, and released same year. Adult drakes dosed with four in late winter months, 1950 and 1951, by pellets each in 1951 had a year-of-banding Johnson A. Neff and Charles C. Sperry mortality rate that was slightly, and unac- of the U. S. Fish and Wildlife Service countably, lower than that of birds of the and Irving R. Foley of the Colorado De- same sex and age class dosed with two pel- partment of Game and Fish, table 28. lets each in 1950. Band data for 1951 were not used be- Juvenile drake mallards in 1950 and cause, as Neli (letter, February 5, 1955) 1951 had lower year-of-banding mortality reported, a chemical pollution of the water Table 28.—Number and per cent of bands recovered, 1950-1954, from mallards trapped, banded, and released at the Rocky Mountain Arsenal, Denver, Colorado, February 13-March 21, 1950. Before release, half of the males and half of the females were dosed with six No. 6 shot pellets each, and the others were released, undosed, to serve as controls.* Sex 276 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 between drakes that ingest six lead pellets the populations: In mallard drakes, one each and those that ingest no lead is ap- No. 6 shot pellet per bird produces an in- proximately 3 to 1. The difference in crease in the mortality rate of about 9 per band recoveries between undosed and cent (12.6 and 3.4, 15.0 and 4.9 aver- dosed hens was so slight as to indicate lit- aged) ; two pellets about 23 per cent (43,6 tle mortality from lead poisoning. and 3.4 averaged) ; four pellets about 36 An apparent reason for the large dif- per cent ; and six pellets about 50 per cent. ference in the mortality rates between the Because of the smaller number of ex- Colorado drakes and hens is that in late periments conducted with hens than with winter and early spring hens are less sus- drakes, it is more difficult to appraise ceptible than drakes to lead poisoning. mortality from lead poisoning in the hens. Illinois experiments made with captive However, the available data suggest that, mallards under controlled conditions among hens and drakes with identical in- showed that during the spring hens are gested shot levels, hens probably suffer less susceptible to lead poisoning than are twice as great a mortality as drakes in the drakes (Jordan & Bellrose 1951:21). fall and a small fraction of the mortality With the approach of the breeding season, of drakes in late winter and spring. the consumption of food by captive hens greatly increased until it exceeded that by PREVENTING LEAD captive drakes. Apparently the greater POISONING food consumption by hens during this par- ticular period was the primary factor re- When Green & Dowdell (1936) re- sponsible for the greater survival rate of ported on the apparent feasibility of a the Colorado hens. Illinois data suggest lead-magnesium alloy shot for the preven- that, during the fall, hen mallards are tion of lead poisoning in waterfowl, con- much more susceptible than drakes to lead servationists anticipated the eventual de- poisoning. The year-of-banding mortality velopment of this or some other shot that rate for wild, free-flying mallard hens would prove to be nontoxic to waterfowl dosed with one No. 6 lead pellet each was and acceptable to hunters. However, no about one-fourth greater than the highest shot (with the possible exception of iron year-of-banding mortality rate for mallard shot) has been developed which meets the drakes similarly dosed, table 27. Among requirements of both nontoxicity to water- penned mallards, the mortality rate of fowl and present shooting standards. hens was approximately double the mor- A study of shot alloys by Jordan &: talitv rate of drakes except in spring ( Jor- Bellrose (1950) at the Havana labora- dan '& Bellrose 1951:21). tory of the Illinois Natural History Sur- As shown by differences in mortality vey did not substantiate the findings of rates between dosed and undosed birds, at Green & Dowdell (1936:487-8) that each shot level tested juvenile drakes were lead-magnesium shot, upon its disintegra- much less susceptible to lead poisoning tion in the gizzard of a duck, fig. 8, did than were adult drakes, table 27. The not cause lead poisoning. On the con- lower susceptibility of the juveniles was trary, Jordan & Bellrose (1950:166-7) more marked at the one- and two-shot found that lead-magnesium shot, in spite levels than at the four-shot level. The of its disintegration in the gizzard, was greater food intake by juveniles seems to as toxic as commercial lead shot. account for their lower susceptibility (Jor- Two other types of lead alloy shot dan & Bellrose 1951:20). tested by Jordan & Bellrose (1950: There is good evidence that the drake 165-7), lead-tin-phosphorus shot and class of the mallard population is com- lead-calcium shot, were not less toxic than posed almost equally of adults and juve- commercial shot. niles. The following mortality rates have A proposal to coat commercial shot pel- been calculated on the assumption that lets with a nylon plastic was investigated. the numbers of adults and juveniles are Theoretically, at least, pellets so coated equal and that the percentages on which would have a good opportunity to pass the rates are based (in farthest right out of the gizzard before the plastic was column of table 27) hold true throughout abraded away and the lead exposed. It May, 1959 Bellrose: Lead Poisoning in Waterfowl 277 per cent) Fig 8—The breakup of three lead alloy shot pellets containing magnesium (2 after ingestion; C 96 hours in the gizzard of a mallard; A, 1 hour after ingestion; B, 24 hours the gizzard has failed to expel after ingestion; £), 144 hours after ingestion. As shown in D, in the gizzard, the lead alloy a large proportion of the lead particles. Despite its disintegration shot containing magnesium was as toxic as commercial lead shot. 278 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 Table 29.—Relative eflFectiveness of iron shot and commercial lead shot as measured by the per cent of sample (game-farm mallards) bagged with No. 4 and No. 6 shot fired from 12-gauge full-choke gun at each of four ranges, 1950 and 1951. ; May, 1959 Bellrose: Lead Poisoning in Waterfowl 279 of gun barrels, and range limitations were was that an iron shot acceptable for most for the most part overcome. A special shot shell requirements could be produced. shooting process (Patent No. 2,544,678) However, the required manufacturing in- was developed. By repeated annealing in vestment would be large, and this factor, furnaces with controlled atmospheres, the coupled with uncertainty concerning cus- iron alloy was substantially reduced in tomer acceptance, convinced Winchester- hardness. Many thousands of shot shells Western that manufacture of iron shot fired with iron shot loads showed that was not feasible unless drastic action was soft iron had little, if any, adverse effect needed to save waterfowl from serious on modern gun barrels and adjustable lead poisoning losses. chokes. If drastic action should at any time be One of the principal disadvantages of necessary, the U. S. Fish and Wildlife using iron shot for shot shell loads is that Service could require waterfowl hunters its lower density reduces its effectiveness to shoot only shells containing iron shot at maximum ranges. In 1950 and 1951, shells with such a load could be so marked the relative killing power of iron shot and that inspection by conservation officers of lead shot was investigated by shooting would insure compliance with regulations. game-farm mallards under controlled con- ditions (Bellrose 1953:353-5). DISCUSSION No. 4 and No. 6 shot were used at ranges of 35, 40, 50, and 60 yards, table The incidence of ingested lead shot in 29. Iron shot and lead shot fired from a the segment of a duck population har- 12-gauge, full-choke gun showed no differ- vested by waterfowlers is not representa- ence in killing power at 35 yards, but tive of the entire population nor the en- iron shot declined in relative effectiveness tire year. It is representative of only a as the ranges increased. part of the population (the segment har- At ranges of 35 and 40 yards, the num- vested) and a short period of time (the ber of pellets hitting the trunks of ducks time of sampling). averaged higher for iron shot than for The percentage of ducks that have in- lead shot, table 30. For comparable ranges gested shot at some time during the year, and shot sizes, the percentage of pellets or during the period in which most inges- hitting the trunks that penetrated to the tion of shot occurs, may be calculated body cavities was greater for lead shot. through application of correction factors hits registered The greater number of that take into account ( 1 ) the fact that on game-farm ducks by iron shot than by ducks carrying lead are more vulnerable lead shot at the short ranges can be ex- to hunting than are lead-free ducks and plained by the larger load of iron pellets (2) the fact that most ducks ingesting lead in each shot shell. Because of the lower either void the lead or die of poisoning density of iron, more iron pellets than within about 4 weeks. lead pellets of the same size can be loaded As shown by experiments in which in a shot shell having the same powder wild mallards were trapped, banded, and charge. A standard 12-gauge duck load released, some dosed with lead and others contains about 169 No. 4 lead pellets; not dosed, the birds dosed with one No. 6 such a load would contain about 250 iron shot pellet each were about 1.5 times pellets. Because the impact potential of (1.19-1.84, table 20) as vulnerable to shot at long range increases with increases hunting as were the controls; those dosed in size of shot, some compensation can be with two pellets each were 1.89 times as made for the relative decline in killing vulnerable as the controls; and those power of iron shot at long range by using dosed with four pellets each were 2.12 iron shot one size larger than that custo- times as vulnerable. The incidence of marily used in lead shot, that is. No. 4 lead in an entire population at any one instead of No. 5 in a given situation. time is therefore less than the incidence There are no insurmountable obstacles of lead in the segment of the population to the use of iron shot for waterfowl hunt- taken by hunters ; for the populations dis- ing. The conclusion which Winchester- cussed in this paper the incidence of lead Western drew from extensive research can be calculated by applying 1.5, 1.9, and 280 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 2.1 as correction factors at the one-, two-, The penned wild mallards that were and four-pellet levels. dosed by Jordan with one No. 6 shot pel- Application of the correction factor de- let each and that showed few or no indi- signed to nullify hunting bias at the one- cations of lead poisoning had eliminated pellet level indicates that during the hunt- the pellets by the thirty-first day. The ing season an average of 2.96 per cent of average period of lead retention by the the mallards of North America are car- ducks in this category was 18 days. Mal- rying one ingested lead pellet each, table lards that were dosed with two or with 31. The application of correction factors four pellets each and that showed no sig- at other shot levels is shown in table 31. nificant manifestation of lead poisoning The correction factors for three-, five-, had eliminated the pellets about as rap- and six-plus-pellet levels were derived idly as those dosed with one pellet each. through interpolation or extrapolation. The penned mallards that were dosed Daily during the fall and winter with one No. 6 shot pellet each and that months, some ducks in the North Ameri- showed moderate to severe effects of lead can population are ingesting shot pellets, poisoning had eliminated no pellets in the some are voiding them, some are dying first week; at the end of 4 weeks, only 27 from their effects, and some are recover- per cent of these ducks had voided all the ing. pellets with which they had been dosed. Unpublished Natural History Survey Twenty-one per cent of 119 penned reports of laboratory studies by James S. mallards that had eliminated all shot pel- Jordan show that penned wild mallards lets they had been given (one to four that have ingested one or more No. 6 shot pellets each) died from lead poisoning. A pellets each may eliminate the pellets as study of the history of these ducks led to early as the first week after ingestion or the conclusion that a large proportion of they may retain them as long as several the ducks that retain lead shot for 3 or weeks, until the pellets have become thin more weeks die from its effects. wafers 0.05 inch or less in diameter. The As previously discussed, most mallards appearance of lead pellets that have spent in the wild that die from lead poironin:; various periods of time in the gizzards of perish in the second or third week after ducks is shown in fig. 9. thev have ingested lead. Most mallards Table 31.—Estimated percentages of North American mallard population lost as a result of lead poisoning. The figures for the various shot levels have been corrected for hunting bias and population turnover. (By shot level is meant the number of ingested shot pellets found in the gizzard of a duck.) ; May, 1959 Bellrose: Lead Poisoning in Waterfowl 281 that ingest lead have either died or re- populations ingest lead shot. Malysheff covered within 4 weeks. (1951), after making chemical analyses Observations in the field and in the for lead in the bones and livers of water- laboratory indicate that a mallard that fowl taken in the Lower Fraser Valley of survives ingestion of lead will have elim- British Columbia, reported that 52.1 per inated the lead 18 days, on the average, cent of the 79 mallards he examined had after ingestion ; a mallard that dies with at one time or another in their lives in- lead still in its gizzard will die 21 days, gested lead ; at the time of examination on the average, after ingestion. Because only about 16 per cent of the mallards of these observations, 20 days have been had lead in their gizzards and about 36 Fig. 9.—The appearance of No. 6 lead shot pellets that spent various periods of time in the gizzards of ducks. chosen as the average period of turnover per cent had survived previous lead inges- of leaded mallards in the wild. tion. Malysheff found that 38.2 per cent As indicated by the presence of lead in of 35 pintails showed evidence of lead duck gizzards collected from hunters and 22.9 per cent had lead in their gizzards by lead poisoning die-offs, the lead poison- at the time of examination, and approxi- ing "season" (the period of greatest ex- mately 15 per cent had survived previous posure to lead deposited in feeding areas lead ingestion. from the guns of hunters) is a 120-day Mortality rates for Mississippi Flyway period that begins with November and mallards dosed with lead shot are pre- ends with February. If, as believed, mal- sented in table 31 ; the figures have been lard gizzards collected at any one time adjusted for survival differences between are representative of only a 20-day turn- adults and juveniles, as discussed on page over period, the number of mallards in- 276. Figures for dosages of three, five, gesting lead in the 120-day lead poison- six, and six-plus pellets have been derived ing "season" is six times the average of by interpolation or extrapolation. the numbers obtained from samples taken If the lead poisoning mortality rates in the "season." Then the factor to be for mallards in other parts of North used in correcting for turnover is 6. America are approximately the same as This correction factor applied to inci- in the Mississippi Flyway, then for the dence figures corrected for hunting bias entire North American mallard popula- indicates that approximately one-fourth tion the annual loss due to lead poisoning of the wild mallards of North America in can be calculated, table 31. The figure any one year ingest lead shot, table 31. 1.60 derived for the per cent of the mal- There is evidence that a much larger lard population lost as a result of inges- proportion than one-fourth of some duck tion of one shot pellet per duck has greater 1 282 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 reliability than the other figures, as it is of the pintail is evinced by the rela- based on a greater number of field data. tively lower losses among ducks of this The calculations on which the figures species on areas where both pintail and in table 31 are based have many shortcom- mallard have been involved in important ings. However, the figure 3.98 arrived lead poisoning die-offs, table 1. at as the percentage of the mallard popu- The extremely low shot incidence lation lost as a result of ingestion of lead found in the blue-winged teal, green- shot is at least a "calculated estimate." winged teal, shoveler, and wood duck The figures in table 31 need qualifica- precludes lead poisoning as a cause of ap- tion and interpretation. They do not take preciable losses in these species. In addi- into account the number of mallards car- tion to having a low rate of shot inges- rying lead that are harvested by hunters tion, the baldpate and the gadwall feed and so are not wasted. Because ducks largely upon leafy aquatic vegetation, food carrying lead are more vulnerable to highly beneficial in alleviating the effects hunting than are ducks that are free of of ingested lead ; mortality from lead poi- lead, table 20, a considerable proportion soning is considered to be almost negli- of the mallards classified as lost in table gible in these species. 31 are bagged by hunters. The results of Noticeable lead poisoning die-offs are twice-weekly surveys of public shooting extremely rare in the redhead, ring-necked grounds in central Illinois during recent duck, canvasback, and lesser scaup, table hunting seasons indicate that the waste, 1 , even though these species have the high- or unharvested loss, due to lead poisoning est incidence of ingested shot recorded is about one-fourth less than the 3.98 per among waterfowl, table 11. It must be cent calculated as the total loss, or ap- concluded, therefore, that lead poisoning proximately 3 per cent. is not an important mortality factor in The estimated 3 per cent waste due to ducks of the genus Aythya. This fact lead poisoning represents day-to-day, non- seems attributable to their beneficial diets. catastrophic losses and does not include In spite of a low rate of shot ingestion such spectacular losses as those associated by Canada, blue, and snow geese, table 11, with die-offs, in which large proportions these species have become victims of lead of localized populations fall victim to lead poisoning die-offs on a surprisingly large poisoning. On the basis of data in table number of occasions, table 1, but, in each 1, it is estimated that, for mallards of the case, the per cent of the population lost has Mississippi Flyway, to the 3 per cent been low. Inasmuch as these geese feed waste mentioned above should be added primarily on corn in the areas where the 1 per cent to cover the die-off losses, a die-offs have occurred, diet appears as an total of 4 per cent. For mallards of other important factor contributing to their flyways, the die-off losses are markedly mortality. less, table 1. As mentioned above, approximately 4 Mallards have made up the bulk of the per cent of the mallard population of the ducks found in important lead poisoning Mississippi Flyway is wasted annually as die-offs in the United States in recent a result of lead poisoning. The annual years, table 1. This fact is construed to mallard waste in other flyways is esti- mean that the mallard is more susceptible mated to be between 3 and 4 per cent. to lead poisoning than other species of The annual waste due to lead poisoning waterfowl. among all species of waterfowl in all Most available evidence points to the North American flywavs is estimated to pintail as the species second to the mallard be between 2 and 3 per cent of the popu- in susceptibility to lead poisoning, table 1. lation. Malyshef? (1951) found the pintail even Several students of waterfowl have more susceptible than the mallard in feared that in addition to direct losses due possible indi- small samples taken in British Columbia. to lead poisoning there are | Although, as table 1 1 indicates, in North rect losses, such as lead-induced sterility. America as a whole a greater percentage Wetmore (1919:11) and Shillinger & of pintails than of mallards ingested shot, Cottam (1937:400) are among the au- the influence of the more beneficial diet thors who have voiced concern over possi- May, 1959 Bellrose: Lead Poisoning in Waterfowl 283 ble sterility. This concern has been fos- problem that should concern every sports- tered by evidence that lead reduced the man. Birds that die from lead poisoning virility of domestic poultry and acted as suffer for 2 or 3 weeks preceding death. an abortifacient in mammals. In two laboratory studies which have SUMMARY been made on the effect of ingested lead on sterility in waterfowl, the conclusion 1. The mortality resulting from lead was reached that the lead had little per- poisoning in wild waterfowl has been a ceptible effect upon reproduction. Of the cause of concern to conservationists for first study, with game-farm mallards, many years. Cheatum & Benson (1945:29) stated 2. A publicized die-off of ducks from that: "These few data indicate that among lead poisoning near Grafton, Illinois, in the mallard drakes used, those which re- January, 1948, brought the problem to covered from lead poisoning did not ex- the attention of officials of the Western hibit a significant loss of fertility." From Cartridge Company (now Winchester- the second study, in 1948 and 1949, in Western Cartridge Division of Olin which both drake and hen game-farm mal- Mathieson Chemical Corporation) and lards were used, Elder (1954:322) con- the Illinois Natural History Survey. This cluded that: "Leaded birds received 18 resulted in a joint research project on shot while on a grain diet, and the result- lead poisoning in waterfowl ; research was ing toxemia was very severe. However, conducted largely at the field laboratory normal birds did not exceed leaded birds of the Survey on the Chautauqua Na- in fertility, embryonic success, or hatch- tional Wildlife Refuge, Havana. ability. But in both years the normal hens 3. The objects of the research project surpassed leaded hens in fecundity for the were threefold: (1) evaluation of losses season." from lead poisoning in wild waterfowl, Rarely do waterfowl in the wild ingest (2) investigation of lead alloys and other as many as 18 shot pellets per duck, and materials for possible use as nontoxic shot, seldom do waterfowl in the wild recover and (3) determination of the physiologi- from toxemia as severe as that exhibited cal effects of lead poisoning on waterfowl. by ducks in the 1949 experiments by This paper is concerned primarily with an Elder. evaluation of the losses from lead poison- At the present time, lead poisoning ing. losses in waterfowl do not appear to be 4. The approach toward evaluating of sufficient magnitude to warrant such the importance of lead poisoning involved drastic regulations as, for example, prohi- appraisal of (1) the incidence and mag- bition of the use of lead shot in water- nitude of waterfowl die-offs resulting fowl hunting. Should lead poisoning be- from lead poisoning, (2) the incidence come a serious menace to waterfowl pop- of ingested lead shot among waterfowl ulations, iron shot provides a possible populations in fall and early winter, and means of overcoming it. (3) the extent of waterfowl losses result- Although lead poisoning apparently ing from the ingestion of various quanti- does not at the present time cause mor- ties of lead shot. tality of such magnitude as to endanger 5. The history of lead poisoning in the North American waterfowl popula- North American waterfowl dates back to tion, it nevertheless poses an important the latter half of the nineteenth century. problem for the future. In the past, the Losses in the nineteenth century or early incidence of lead poisoning has increased twentieth century were reported from as numbers of waterfowl hunters have in- Stephenson Lake and Lake Surprise, creased. Because further increases in the Texas; Currituck Sound, North Caro- numbers of these hunters are expected, lina; Puget Sound, Washington; Back the search for the best possible solution to Bay, Virginia; and Hovey Lake, Indiana. the lead poisoning problem should be con- 6. A survey conducted among state tinued. and federal conservation agents and agen- From a compassionate as well as a man- cies indicates that in recent years the agement viewpoint, lead poisoning is a waterfowl losses from lead poisoning have 284 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 been largest in the Mississippi Flyway volved, (4) the depth of water above the and have been followed in order by losses bottom, and (5) ice cover. in the Pacific, Central, and Atlantic fly- 13. The extent to which various spe- ways. cies of waterfowl are exposed to shot pel- 7. In recent years, certain areas in the lets on the bottoms of marshes and lakes United States have been the scenes of is influenced by the feeding habits of the several sizable die-offs of waterfowl af- birds and by the kinds of food avail- fected by lead poisoning. Among these able, as well as by the numbers of shot areas are Catahoula Lake, Louisiana; pellets available. Claypool Reservoir, Arkansas ; Lake 14. The incidence of ingested shot pel- Chautauqua National Wildlife Refuge, lets in migrating waterfowl populations Illinois ; and Squaw Creek National was determined by ( 1 ) fluoroscopic ex- Wildlife Refuge, Missouri. amination of live-trapped ducks, (2) com- 8. Most of the notable waterfowl die- pilation of data obtained from investi- oi^s from lead poisoning have occurred in gators who had examined waterfowl giz- late fall and early winter months, after zards for food content, and (3) fluoro- the close of the hunting seasons. Few scopic and direct examination of gizzards, losses of ducks have been noted in the numbering many thousands, obtained spring, but losses of whistling swans and from ducks in hunters' bags. of Canada, blue, and snow geese have 15. Fluoroscopy of trapped ducks been reported at that time. There are no caught at baited traps on a heavily shot- recent records of waterfowl succumbing over area revealed that the birds had in- from lead poisoning during the summer gested abnormally large numbers of shot months. pellets. Among three species, blue-winged 9. The mallard has been the principal teal, wood duck, and pintail, feeding to- species involved in sizable lead poisoning gether, there appeared to be a relation die-offs across the nation. The pintail has between the percentage of ducks ingest- predominated in losses recorded in the ing shot pellets and the size of individuals. Pacific Flyway. Where both species oc- The species with the largest individuals cur together in the Mississippi Flyway, had the highest percentage of individuals losses in the mallard have been relatively with ingested lead. In two of the species, higher. an appreciably greater percentage of juve- 10. In the Mississippi Flyway, 1938- niles than of adults carried ingested lead. 1955, 10.4 per cent of the mallard drakes 16. Fluoroscopy by wildlife techni- and 13.0 per cent of the mallard hens cians on waterfowl breeding grounds dur- picked up in die-offs carried no ingested ing the summer months revealed a low shot. In experiments with penned mal- incidence of ingested shot among ducks lards dosed with one to four No. 6 shot in Utah and Saskatchewan, but a high pellets each, 21 per cent voided shot be- incidence among those at the Delta fore death. These figures suggest that Marsh, Manitoba, which is one of the birds in the wild that succeed in voiding most heavily shot-over areas in Canada. shot are more likely to survive than are 17. Examination of 36,145 gizzards of penned birds that void shot. waterfowl bagged by hunters in North 11. Data from four widely separated America revealed many differences among areas in which die-offs of mallards oc- species in incidence of ingested lead. Less curred indicate that differences between than 1 per cent of the Canada geese and the areas in the numbers of ingested shot less than 3 per cent of the blues and snows pellets per drake resulted mainly from dif- had lead in their gizzards. Among the ferences in availability of shot and in diet ducks, the percentages carrying ingested of ducks in the die-off areas. lead were as follows: less than 2 per cent 12. The availability of lead shot pellets of the buffleheads, green-winged teals, to waterfowl on a particular body of mergansers, wood ducks, shovelers, and water is determined by (1) the shooting gadwalls; between 2 and 5 per cent of intensity, or amount of shot on the bot- the blue-winged teals, baldpates, and I tom, (2) the firmness of the bottom ma- common goldeneyes; between 5 and 10 terial, (3) the size of the shot pellets in- per cent of the ruddy ducks, mallards, May, 1959 Bellrose: Lead Poisoning in Waterfowl 285 black ducks, and pintails; more than 10 24. Among the dosed wild mallards, per cent of the canvasbacks, lesser scaups, the ingestion of lead shot pellets did not redheads, and ring-necked ducks. appear to affect behavior until after the 18. A study of the feeding habits of first 5 days. Among birds dosed with one the various species of ducks in relation to shot pellet each, and that did not die of shot incidence indicated that grit prefer- lead poisoning, the period of affliction ap- ences do not influence shot ingestion. peared to persist for about 15 days; 19. The incidence of ingested lead among those dosed with two to four shot shot was lowest among waterfowl of the pellets each, the period was longer. Central Flyway, higher among those of 25. The weakness and fatigue appar- the Atlantic, slightly higher still among ent in dosed wild mallards that suffered those of the Pacific, and highest among from lead poisoning reduced the ability those of the Mississippi Flyway. State of the ducks to migrate. The larger the and local variations in shot incidence number of ingested shot pellets per bird, within each flyway were numerous. The the greater was the reduction in move- incidence of ingested lead was more than ment. Band recoveries from a group of twice as high among ducks taken along mallards dosed with four pellets each the Illinois River as among those taken showed that less than 5 per cent of the along the Mississippi. birds migrated farther than 50 miles from 20. Examination of live and hunter- the banding station at which they were killed ducks indicated that much of the dosed. lead ingested by waterfowl had been fired 26. Among the dosed wild mallards in from the guns of hunters in the season of 1950 and 1951, at each dosage level the ingestion. Apparently, much of the shot mortality rate from lead poisoning was fired during a hunting season eventually higher for adult drakes than for juvenile penetrated so deep into lake and marsh drakes. During the fall months, mortality bottoms that by the following summer it was higher among hens than among was out of the reach of waterfowl. drakes, but by late winter the situation 21. Increases in the percentage of wa- was reversed. Differences in mortality terfowl ingesting lead have paralleled in- rates among mallards of different ages and creases in the number of waterfowl hunt- sexes were attributed primarily to differ- ers. Because there is expectation that the ences in the quality and quantity of food number of duck hunters will continue to consumed. increase, it can be anticipated that lead 27. In a population of wild mallard poisoning will become more prevalent drakes, a population made up equally of among waterfowl than it is at present. adults and juveniles, one No. 6 pellet per 22. The magnitude of the shot level bird is estimated to cause an increase in (number of pellets in a gizzard) has an mortality rate of about 9 per cent, two important bearing on the rate of mortality pellets per bird an increase of about 23 of waterfowl. Among 2,184 gizzards con- per cent, four pellets per bird an increase taining lead shot, 64.7 per cent contained of about 36 per cent, and six pellets per only one pellet each, 14.9 per cent con- bird an increase of about 50 per cent. tained two pellets each, and only 7.4 per 28. An effort to find a lead alloy shot cent more than six pellets each. pellet that was nontoxic to waterfowl was 23. A field experiment showed that unsuccessful. However, iron shot was ducks afflicted with lead poisoning dur- found to be nontoxic. Most of the diffi- ing the hunting season are more likely to culties yjl manufacturing iron shot pellets be bagged than are healthy birds. Wild were overcome by technicians of the Win- mallards that were dosed with one No. 6 chester-Western Cartridge Division of shot pellet each and released were 1.5 the Olin Mathieson Chemical Corpora- times as vulnerable to hunting as were tion. At present the principal disadvan- undosed controls ; those dosed with two tage in using iron shot pellets for water- shot pellets each were 1.9 times as vul- fowl hunting is that they are less effec- nerable ; and those dosed with four shot tive at maximum ranges than are lead pellets each were 2.1 times as vulnera- pellets. ble. 29. In determining the importance of 286 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 lead poisoning in a waterfowl population, ii. Two studies made outside of Illi- it is necessary to eliminate the hunting nois indicate that lead poisoning in water- bias of samples and to ascertain the period fowl does not seriously curtail the repro- of turnover of migrating mallards that ductive capacity of ducks that recover are carrying lead in their gizzards. from the malady. 30. Incidence figures corrected for 34. At the present time, lead poison- hunting bias and turnover suggest that ing losses do not appear to be of sufficient approximately one-fourth of the wild mal- magnitude to warrant such drastic regu- lards of North America in any year in- lations as, for example, prohibition of the gest lead shot. use of lead shot in waterfowl hunting. 31. It is estimated that, each year, ap- Should lead poisoning become a more se- proximately 4 per cent of the mallards in rious menace to waterfowl populations, the Mississippi Flyway die in the wild as iron shot provides a possible means of a result of lead poisoning and that an ad- overcoming it. Because of the increasing ditional 1 per cent of the mallards in the numbers of waterfowl hunters and the flyway are afflicted with lead poisoning increasing incidence of lead poisoning, as but are bagged by hunters. well as because of the suffering that re- 32. For all waterfowl species in North sults among "waterfowl seriously afflicted America, the annual loss due to lead poi- with the malady, the search for the best soning is estimated to be between 2 and 3 possible solution to the lead poisoning per cent of the population. problem should be continued. LITERATURE CITED Ayars, James Sterling 1947. Lead on the loose. Sports Afield 118(6): 24-5, 92-4. Bellrose, Frank C. 1947. Ducks and lead. 111. Cons. 12(1): 10-1. 1951. Effects of ingested lead shot upon waterfowl populations. N. Am. Wildlife Conf Trans. 16:125-33. 1953. A preliminary evaluation of cripple losses in waterfowl. N. Am. Wildlife Conf Trans. 18: 337-60. 1955. A comparison of recoveries from reward and standard bands. Jour Wildlife Mgt 19(l):71-5. Bellrose, Frank C, and Elizabeth Brown Chase 1950. Population losses in the mallard, black duck, and blue-winged teal. 111. Nat. Hist. Surv. Biol. Notes 22. 27 pp. Bowles, J. H. 1908. Lead poisoning in ducks. Auk 25(3): 312-3. Cheatum, E. L., and Dirck Benson 1945. Effects of lead poisoning on reproduction of mallard drakes. Jour. Wildlife Mgt 9(1) :26-9. Cottam, Clarence 1939. habits of diving Food North American ducks. U. S. Dept. Ag. Tech. Bui. 643. 140 pp. 1949. Further in n?eds wildlife research. Jour. Wildlife Mgt. 13 (4) : 333-41. Elder, William H. 1950. Measurement of hunting pressure in waterfowl by means of X-ray. N. Am. Wildlife Conf. Trans. 15:490-503. 1954. The effect of lead poisoning on the fertility and fecundity of domestic mallard ducks Jour. Wildlife Mgt. 18(3) : 315-23. Creen, R. G., and R. L. Dowdell 1936. The prevention of lead poisoning in waterfowl by the use of disintegrabie lead shot N. Am. Wildlife Conf. Proc. 1 :486-9. Grinnell, George Bird 1894. Lead poisoning. Forest and Stream 42(6): 117-8. 1901. American duck shooting. Forest and Stream Publishing Company, New York. 627 pp. Hartmeister, Felix A., and Martin J. Hansen 1949. The incidence of lead shot in three important Wisconsin waterfowl areas. Wis. Wild- life Res. Quart. Prog. Reps. 8(3):18-22. Heuer, Wayne H. 1952. The incidence of lead shot in waterfowl of the Pacific Flyway, with special reference to the Great Salt Lake Basin. Master's thesis, LTtah State Agricultural College, Logan. 49 pp. Hough, E. 1894. Lead-poisoned ducks. Forest and Stream 42(6) : 117. Hunt, George S., and Howard E. Ewing 1953. Industrial pollution and Michigan waterfowl. N. Am. Wildlife Conf. Trans. 18:360-8. Jones, John C. 1940. Food habits of the American coot with notes on distribution. U. S. Biol. Surv. Wildlife Res. Bui. 2. 52 pp. Jordan, James S., and Frank C. Bellrose 1950. Shot alloys and lead poisoning in waterfowl. N. Am. Wildlife Conf. Trans. 15:155-68. 1951. Lead poisoning in wild waterfowl. 111. Nat. Hist. Surv. Biol. Notes 26. 27 pp. McAtee, W. L. 1908. 'Lead poisoning in ducks.' Auk 25(4): 472. Malysheff, Andrew 1951. Lead poisoning of ducks in the Lower Eraser Valley of British Columbia: a chemical study. Master's thesis. University of British Columbia, Vancouver. 90 pp. Martin, Alexander C, Herbert S. Zim, and Arnold L. Nelson 1951. American wildlife and plants. McGraw-Hill Book Company, Inc., New York. 500 pp. Martin, Dale N. 1957. Quarterly progress report, waterfowl investigation. Ind. Pittman-Robertson Wildlife Res. Rep. 18(2):112-7. [287] 288 Illinois Natural History Survey Bulletin Vol. 27, Art. 3 Mohler, L. 1945. Lead poisoning of geese near Lincoln. Nebr. Bird Rev. 13(2):49-50. Munro, J. A. 1925. Lead poisoning in trumpeter swans. Can. Field Nat. 39(7): 160-2. Phillips, John C, and Frederick C. Lincoln 1930. American waterfowl. Houghton Mifflin Company, Boston and New York. 312 pp. Pirnie, Miles David 1935. Michigan waterfowl management. Michigan Department of Conservation, Lansing. 328 pp. Reid, Vincent H. 1948. Lead shot in Minnesota waterfowl. Jour. Wildlife Mgt. 12(2) : 123-7. Shillinger, J. E., and Clarence C. Cottam 1937. The importance of lead poisoning in waterfowl N. Am. Wildlife Conf. Trans. 2:398-403. Stall, J. B., and S. W. Melsted 1951. The silting of Lake Chautauqua. 111. Water Surv. Rep. Invest. 8. 15 pp. Suter, Max 1948. Temperature and turbidity of some river waters in Illinois. 111. Water Surv. [Rep. Invest. IJ. 14 pp. Tener, John G. 1948. An investigation of some of the members of the sub-family Anatinae in the Lower Fraser Valley of British Columbia. Master's thesis, University of British Columbia, Vancouver. 66 pp. Van Tyne, Josselyn 1929. The greater scaup affected by lead poisoning. Auk 46(1) : 103-4. Wetmore, Alexander 1919. Lead poisoning in waterfowl. U. S. Dept. Ag. Bui. 793. 12 pp. Yancey, Richard K. 1953. Lead poisoning on Catahoula Lake. La. Cons. 5(5):2-5. «Vv,^>J5,i Some Recent Publications of the Ilunois Natural History Survey BULLETIN BIOLOGICAL NOTES Volume 26, Article 3.—Natural Availability 29.—An Inventory of the Fishes of Jordan of Oak Wilt Inocula. By E. A. Curl. June, Creek, Vermilion County, Illinois. By R. 1955. 48 pp., frontis., 22 figs., bibliog. Weldon Larimore, Quentin H. Pickering, Volume 26, Article 4.—Efficiency and Selec- and Leonard Durham. August, 1952. 26 tivity of Commercial Fishing Oevicet Uaed pp., 25 figs., bibliog. on the Mississippi River. By William C. 30.---Sport Fishing at Lake Chautauqua, near Starrett and Paul G. Baroickol. July, Havana, Illinois, in 1950 and 1951. By 1955. 42 pp., frontis., 17 figs., bibliog. William C. Starrett and Perl L. McNeil, Volume 26, Article 5.—Hill Prairies of Illi- Jr. August, 1952. 31 pp., 22 figs., bibliog. nois. By Robert A. Evers. August, 1955. 31.—Some Conservation Problems of the 80 pp., frontis., 28 figs., bibliog. Great Lakes. By Harlow B. Mills. Octo- Volume 26, Article 6.—Fusarium Disease of ber, 1953. (Second printing.) 14 pp., illus., Gladiolus: Its Causal Agent. By Junius L. bibliog. Forsberg. September, 19S5. 57 pp., frontis., 33.—A New Technique in Control of tlkC 22 figs., bibliog. House Fly. By Willis N. Bruce. Decem- Volume 27, Article 1.—Ecological Life History ber, 1953. 8 pp., S figs. of the Warmouth. By R. Weldon Larimore. 34.—White-Tailed Deer Populations in Illi- August, 1957. 84 pp., color frontis., 27 figs., nois. By Lysle R. Pietscb. June, 1954. 24 bibliog. pp., 17 figs., bibliog. Volume 27, Article 2.—A Century of Biological 35.—An Evaluation of the Red Fox. By Research. By Harlow B. Mills, George C. Thomas G. Scott. July, 1955. (Second Decker, Herbert H. Ross, J. Cedric Carter, printing.) 16 pp., illus., bibliog. George W. Bennett, Thomas G. Scott, James 36.—A Spectacular Waterfowl Migration S. Ayars, Ruth R. Warrick, and Bessie B. Through Central North America. By Frank East. December, 1958. 150 pp., 2 frontis., C. Bellrose. April, 1957. 24 pp., 9 figs. illus., bibliog. $1.00. 37.—Continuous Mass Rearing of the Euro- pean Corn Borer in the Laboratory. By CIRCULAR Paul Surany. May, 1957. 12 pp., 7 figs., 32.—Pleasure With Plants. By L. R. Tehon. bibliog. July, 1958. (Fifth printing, with revisions.) 38.—Ectoparasites of the Cottontail Rabbit in 32 pp., frontis., 8 figs. Lee County, Northern Illinois. By Lewis J. 42.—Bird Dogs in Sport and Conservation. Stannard, Jr., and Lysle R. Pietsch. June, By Ralph E. Yeatter. December, 1948. 64 1958. 20 pp., 14 figs., bibliog. pp., frontis., 40 figs. 39.—A Guide to Aging of Pheasant Embryos, 45.—Housing for Wood Ducks. By Frank C. By Ronald F. Labisky and James F. Opsahl. Bellrose. February, 1955. (Second print- 4 pp., illus., bibliog. ing, with revisions.) 47 pp., illus., bibUog. 46.—Illinois Trees: Their Diseases. By J. MANUAL Cedric Carter. August, 1955. 99 pp., 3.—Fieldbook of Native Illinois Shrubs. By frontis., 93 figs. Single copies free to Illi- Leo R. Tehon. December, 1942. 307 pp., nois residents; 25 cents to others. 4 color pis., 72 figs., glossary, index. $1.75. 47.—Illinois Trees and Shrubs: Their Insect 4.—Fieldbook of Illinois Manunals. By Donald Enemies. By L. L. English. May, 1958. 92 F. Hoffmeister and Carl O. Mohr. June, pp., frontis., 59 figs., index. Single copies 1957. 233 pp., color frontis., 119 figs., glos- free to Illinois residents; 25 cents to others. sary, bibliog., index. $1.75. Li*t of available publleotiona mailmd on rsquaat. Single copies of Illinois Natural History Survey publications for which no price is listed will be furnished free of charge to individuals until the supply becomes low, after which a nominal charge may be made. More than one copy of any free publication may be obtained without cost by educational institutions and official organizations within the State of Illinois; prices to others on quantity orders of these publications will be quoted upon request. Address orders and correspondence to the Chief Illinois Natural History Survey Natural Resources Building, Urbana, Illinois Payment in the form of money order or check made out to State Treasurer of Illinois, Springfield, Illinois, must accompany requests for those publications on which a price is set