Allen Press The Effect of Weather on Bioenergetics of Breeding American Woodcock Author(s): Dale L. Rabe, Harold H. Prince and Erik D. Goodman Source: The Journal of Wildlife Management, Vol. 47, No. 3 (Jul., 1983), pp. 762-771 Published by: Wiley on behalf of the Wildlife Society Stable URL: http://www.jstor.org/stable/3808611 . Accessed: 20/03/2013 09:28 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Wiley, Wildlife Society, Allen Press are collaborating with JSTOR to digitize, preserve and extend access to The Journal of Wildlife Management. http://www.jstor.org This content downloaded from 35.8.11.2 on Wed, 20 Mar 2013 09:28:52 AM All use subject to JSTOR Terms and Conditions THE EFFECTOF WEATHERON BIOENERGETICS OF BREEDINGAMERICAN WOODCOCK' DALEL. RABE,2Department of Fisheriesand Wildlife,Michigan State University,East Lansing,MI 48824 HAROLDH. PRINCE,Department of Fisheriesand Wildlife,Michigan State University,East Lansing,MI 48824 ERIKD. GOODMAN,Department of ElectricalEngineering and System Science, MichiganState University,East Lansing,MI 48824 Abstract: Simulation modeling was used to investigate the impact of weather on the bioenergetics of breeding and postbreeding American woodcock (Scolopax minor). Using air temperature and precipitation as inputs, the model calculates the daily energy requirements of an adult female woodcock and chicks along with the availabilty of their primary food, earthworms (Lumbricidae). Energetics were modeled from previous studies on woodcock and related species. Earthworm availability was modeled from field data collected in northern Michigan. Results suggest that the greatest potential for weather-related stress on woodcock occurs during the brood-rearing period, with nesting being the 2nd most critical time' When simulated earthworm availability during the brood period was compared with reproductive success data, it indicated that the impact of spring weather on earthworm availability is a significant factor affecting chick survival. J. WILDL.MANAGE. 47(3):762-771 Weather patterns are known to affect 1940, Glasgow 1958, Sheldon 1971), are woodcock behavior and extremes are a also affected by weather. Reproduction suspected cause of mortality. Studies have and growth rates have been shown to de- shown that cold spring temperaturescause cline outside an optimal temperature a decline in singing male activity (Duke range (Evans and Guild 1948, Satchell 1966) and that temperature and wind in 1955). More important to woodcock, how- combination affect the timing of spring ever, is the strong influence that soil mois- and fall migrations (Sheldon 1971, God- ture and temperature have on earthworm frey 1974, Coon 1977). However, little is activity and vertical distributionin the soil. known about the influence of weather on When conditions near the surface become mortality, largely because of the difficulty suboptimal, earthwormsrespond by either in finding woodcock and determining the migrating deeper in the soil or entering a cause of death. Mendall and Aldous (1943) state of aestivation (Guild 1948, Reynolds reported instances of nest losses and adult and Jordan 1975, Edwards and Lofty mortality on the breeding grounds follow- 1977) and become unavailable to feeding ing an extended period of inclement woodcock. weather, and Sheldon (1971) and Owen Our objective was to evaluate the direct (1977) believed adverse weather during and indirect effects that weather can have incubation and brood-rearing can cause on woodcock energetics and to identify significant chick mortality. periods of greatest potential impact. Be- Earthworms, which comprise 60-90% cause of the inherent difficulties in gath- of the woodcock diet (Aldous 1939, Sperry ering field data, simulation modeling was used to examine the relationship between energy requirements of woodcock and Michigan Agricultural Experiment Station Paper food 10251. availability. 2 Present address: School of Natural Resources, We thank D. Beaver and G. Dudderar, University of Michigan, Ann Arbor, MI 48109. Michigan State University, and C. Ben- 762 J. Wildl. Manage. 47(3):1983 This content downloaded from 35.8.11.2 on Wed, 20 Mar 2013 09:28:52 AM All use subject to JSTOR Terms and Conditions WOODCOCK BIOENERGETICS * Rabe et al. 763 nett, Michigan Department of Natural metabolic rate (BMR) and costs of ther- Resources, for reviewing earlier drafts of moregulation. Because there has been no this manuscript. We also thank J. Tautin, laboratory measurement of woodcock me- U.S. Fish and Wildlife Service, for sup- tabolism, a BMR estimate of 21.8 kcal/ plying detailed harvest reports for Mich- day was computed from the Aschoff and igan. This work was supported by the Ac- Pohl (1970) equation for non-passerines celerated Research Program for Migratory using an average female weight of 190 g Shore and Upland Game Birds, U.S. Fish (Owen and Krohn 1973). The cost of ther- and Wildlife Service contract 14-16-0008- moregulation was estimated using the 2092, and the Michigan State University general inverse relationship between tem- Agricultural Experiment Station. perature and metabolism discussed by and Farner THE MODEL King (1961), Kendeigh (1969), King (1974), and Ricklefs (1974). For The simulation program (Rabe 1981) temperatures below the thermoneutral was written in FORTRAN IV computer zone (using 10 C as the lower critical tem- language. The model computes daily en- perature), daily BMR was increased 0.12 ergy requirements of an adult female kcal/g/C. Thermoregulatory adjustments woodcock from the time of arrival on due to acclimation at lower temperatures northern breeding grounds to fall migra- have been shown to be small relative to tion and her brood from hatch until dis- total energy requirements in Anatidae bandment, along with the biomass of (Owen and Reinecke 1979) and were not earthworms potentially available to the included. Thermoregulatory costs for birds. Timing of events in the model fol- temperatures above the thermoneutral lows the chronology of breeding and post- zone were not considered important be- breeding activities for the northern Lower cause woodcock generally spend diurnal Peninsula of Michigan. In this part of the periods under a forest canopy. breeding range, woodcock generally be- Total energy cost of activity was ex- gin arriving during mid-March and the pressed as the sum of products for the peak hatch occurs during early May (G. amount of time spent in each activity A. Ammann, pers. commun.). In the mod- (resting, walking, feeding, and flying) el we assumed that adult woodcock do not multiplied by the energy cost for that ac- molt until after the brood has been raised. tivity (expressed as a multiple of BMR). Inputs to the model are daily average Estimates of activity and associated ener- temperature and precipitation. Weather gy costs are given in Table 1. data (1965-80) were obtained from the Nesting energetics included both the National Weather Service at Houghton cost of ovarian development and the cost Lake, Michigan. of producing eggs. The daily reproductive tissue cost estimate of 3.0 kcal was based Hen Energetics on the assumption that the rate of recru- Daily energy requirements of the hen descence is spread equally over a 10-day were divided into 4 components: mainte- period, and that the total energy content nance, activity, nesting, and molting. of the tissue is 30 kcal. Total tissue cost These components were assumed to be in- was based on a mature organ weight of 8 dependent and total energy requirements g (D. L. Rabe, unpubl. data), an energy were obtained by summation. density of 1.9 kcal/g, and a production Maintenance costs included both basal efficiency of 50% (Brody 1945). Cost es- J. Wildl. Manage. 47(3):1983 This content downloaded from 35.8.11.2 on Wed, 20 Mar 2013 09:28:52 AM All use subject to JSTOR Terms and Conditions 764 WOODCOCK BIOENERGETICS* Rabe et al. Table1. Percentageof timewoodcock hen and chicks spend resting, walking, feeding, and flying during different periods. The basalmetabolic rate conversion factor for converting activity to caloricequivalent is included. Hena Chicks Activity Nesting Incubation Brooding Postbrooding Preflight Postflight BMR multipleb Resting 75 83 56 67 57 56 1.3 Walking 16 10 9 13 9 9 2.0 Feeding 18 5 34 16 34 34 2.0 Flying 2 2 1 3 0 1 15.0 a Data from Wenstrom (1973). b Based on studies by Prange and Schmidt-Nielsen (1970), King (1974), and Prince (1979). timates for the eggs are based on a 4-egg limited. To use data from other studies, clutch, laid at a rate of 0.8 egg/day (Shel- growth rates of woodcock chicks were ex- don 1971). The rate of egg development pressed as a percentage of adult weight. was assumed to follow a bell-shaped curve This conversion was made using an aver- (King 1973), and the total energy content age hatch weight of 16 g and a growth of an egg (58 kcal) is based on an average rate of 5.5 g/day (Dwyer et al. 1982) for weight of 17 g (G. A. Ammann, pers. com- the 30-day period modeled. To simplify mun.) and an energy density of 1.7 kcal/ the calculations, an average adult wood- g, again assuming a production efficiency cock weight of 175 g was used rather than of 50%. including separate calculations for each Estimates for the cost of molting were sex. based on the energy content of the feath- Estimates of maintenance energy re- ers.