Immune function and survival of great tit nestlings in relation to growth conditions.

Life history theory predicts a trade-off between number and quality of offspring. Reduced quality with increasing brood size may arise from a decrease in body condition or in immunocompetence that would be important in fighting off virulent parasites by immunologically naive offspring. We tested the effect of rearing conditions on immune function of nestling great tits (Parus major) by reducing or increasing broods by two hatchlings.