Effects of agricultural intensification and temperature on immune response to phytohemagglutinin in Tree Swallows (Tachycineta bicolor)

Abstract

Lower immune response usually translates into lower fitness. Environmental quality can play a key role in shaping immune responses in the wild, as it influences both resource availability and costly maintenance functions. The aim of this study is to evaluate the effect of habitat quality on proinflammatory response to phytohemagglutinin (PHA) in Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) under contrasting agricultural practices. Specifically, we tested the hypothesis that lower quality habitat (intensive agricultural practices and low temperature) negatively impairs immune responses. To do so, we compared the response to PHA of adult female and nestling Tree Swallows nesting in intensive vs. nonintensive agricultural landscapes over 3 years (2008–2010). In accordance with our predictions, we found that habitat quality affected adult female responses to PHA. The response of adult females was significantly higher in nonintensive agricultural areas than in intensive ones. The level of agricultural intensity, however, had no influence on the response to PHA of nestlings. Our results suggest that female adults can buffer the negative impact of a low-quality habitat on their nestlings. Furthermore, our results suggest that under limiting conditions, individuals may have to trade between immunity and other functions such as parental effort.