Document Type


Publication Date

Spring 4-25-2011


Lynn Martin

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Stressors affect immune functions, but exactly why has yet to be discerned entirely. Two non-exclusive hypotheses have been proposed to explain this phenomenon: (i) immunosuppression abates the autoimmune response to self-antigens exposed by the rigors of a stressor, and (ii) immunosuppression allows allocation of resources to functions more valuable than protection against infection during a stressful event, (e.g., physical performance augments predator evasion). In this experiment, the second hypothesis was tested in wild house sparrows (Passer domesticus) by comparing rates of change in vertical flight performance versus antibacterial capacity of blood over a six week period of captivity. I predicted that if the latter hypothesis was true, immune function would decline over time, while physical capability would remain relatively stable, or even increase due to the reallocation of resources. Body mass, vertical hover duration, and antibacterial blood capacity all decreased over time in captivity. However, immune function did not decline more rapidly than physical performance, lending no support to the idea that resources are scavenged from immune function for physical activities. However, the possibility that demands other than vertical flight are traded-off against immune function cannot be dismissed.