Immunity against pathogens comes at an energetic cost and organisms often have to balance investment in immunity with other important processes. For migratory birds, these trade-offs might be especially apparent during the breeding season because of the resources needed for demanding processes like egg-laying or nestling provisioning. We searched for evidence of trade-offs between immunity and investment in costly processes including the corticosterone stress response and reproductive effort and success in a breeding bird. We assayed bacteria killing ability (BKA) of wild female Tree Swallows nesting in boxes, and measured both baseline and stress-induced corticosterone levels. We found no evidence of a trade-off between BKA and the stress response. However, we found that individuals with stronger BKA fed their nestlings at slower rates. Among Tree Swallows, high quality birds breed early in the season, while low quality birds breed later, lay fewer eggs, and fledge fewer young. We found that late-breeding individuals that had stronger BKA laid fewer eggs, while immune capacity was not related to clutch size in early breeders. Despite these differences in reproductive effort, there was ultimately no association between BKA and nestling survival to fledging or number of young fledged. The results suggest that birds in a population do not experience immune trade-offs equally, either because of intrinsic differences among individuals, variation in overall resource availability at different times in the season or shifting resource-allocation priorities throughout the year.