Behavioral Ecology Vol. 11 No. 2: 178-188
© 2000 International Society for Behavioral Ecology
Effects of ambient temperature on avian incubation behavior
a Montana Cooperative Wildlife Research Unit, Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA b U.S.G.S. Biological Resources Division, Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT 59812, USA
Address correspondence to C. J. Conway, Department of Environmental and Forest Biology, State University of New York, Syracuse, NY 13210, USA. E-mail: conway{at}owt.com .
Ambient temperature is commonly thought to influence avian incubation behavior. However, results of empirical studies examining correlations between ambient temperature and bout duration are equivocal. We propose that these equivocal results can be partly explained by developing a conceptual understanding of how we should expect temperature to influence incubation. We demonstrate why linear correlation analyses across a wide range of temperatures can be inappropriate based on development of an incubation model for small birds that incorporates how ambient temperature influences both embryonic development and adult metabolism. We found support for predictions of the model using incubation data from orange-crowned warblers (Vermivora celata) in Arizona. Both off- and on-bout duration were positively correlated with ambient temperature between 9° and 26°C, but unrelated to ambient temperature <9° and 26-40°C. Bout durations declined as ambient temperature approached or exceeded 40°C. Incubating orange-crowned warblers appeared to avoid bouts off the nest <7 min and bouts on the nest <20 min. Time of day, duration of the previous bout, and variation among nests all explained variation in both on- and off-bout duration. Although we found support for the general shape of the incubation model, temperature still explained only a small portion of the overall variation in on- and off-bout duration. Results of previous studies were generally consistent with the model for off-bout duration; most studies in colder environments reported positive correlations with temperature, and the one negative correlation reported was from a hot environment. However, the relationships between on-bout duration and temperature reported in previous studies were less consistent with our model and our data. Although some discrepancies could be explained by considering our model, some studies reported negative correlations in cold environments. The effect of ambient temperature on duration of on-bouts probably differs among species based on the amount of fat reserves females typically carry during incubation and the extent of male incubation feeding. Additional studies of the effects of temperature on avian incubation will help improve the general model and ultimately aid our understanding of energetic and ecological constraints on avian incubation.
Key words: ambient temperature, foraging, incubation behavior, incubation model, incubation rhythm, nest attentiveness, on-bout duration, off-bout duration.
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