Meeting Abstract
In winter and during extreme weather events, natural food abundances may sometimes not be adequate. This unpredictability in resources might then have a negative impact on immune function, as would occur if acquired energy is diverted towards gaining fat and away from maintaining immunity. To test this idea we compared immune function and body composition of three groups of wild black-capped chickadees (Poecile atricapillus) that were given either continuous or intermediate levels of food supplementation or non-food supplemented. Continuously supplemented birds were captured at locations where bird feeders were present and consistently filled from November-March. Intermediately supplemented birds were captured in locations where food was provided from Nov-Jan and then food was removed. Unsupplemented birds were captured at locations where bird feeders were not present. Throughout the course of the study we examined multiple aspects of the immune system (constitutive and induced), body mass, fat and muscle score. Intermediately supplemented birds had higher initial capture fat scores compared to unsupplemented birds. At initial capture, all birds had similar masses; however, continuously supplemented birds had slightly lower muscle scores compared to intermediately supplemented birds. Birds in all groups mounted a similar fever response (change in temperature) to injection with lipopolysaccharide; however, continuously supplemented birds lost slightly less mass after injection compared to the other two groups. Results from this study demonstrate that during times of variable and uncertain food availability, like extreme weather events or long winters, birds are able to buffer themselves against this uncertainty by increasing fat mass, which may in turn impact aspects of the immune system.
