Meeting Abstract
During winter and extreme weather events, temperate residential birds may be faced with an unpredictable availability of food. This variability of resources might then have a negative impact on the bird’s ability to divert resources equally to maintain all important biological functions; moreover, this could impose a trade-off between gaining body fat as a buffer and physiological maintenance (BMR) or thermogenic capacity (Msum). To test this idea we compared the thermal physiology and body composition of captive black-capped chickadees (Poecile atricapillus) with an excess and unpredictable food supply. Control birds received ad libutum food each day of the experiment; birds assigned to the unpredictable treatment received only 80% of their daily energy requirements on random days and ad libitum food on other days. During the course of the study we measured total body mass, fat and lean mass, basal metabolic rate (BMR) and summit metabolic rate (Msum). Treatment birds maintained higher mass over the course of the study and had significantly higher fat mass compared to control birds. First results indicate that Msum was dependent on body mass; however, despite this, Msum was not different between the two groups. Additionally, both groups were similar in their physiological maintenance (BMR). Resulting data from this experiment show that while food unpredictability may cause trade-offs with other biological function (ie. immune response); there does not appear to be a thermogenic cost associated with having an unsteady food supply.
