Meeting Abstract
30.4 Monday, Jan. 5 Bottlenecks, budgets and immunity: the possibility of immune strategies in long distance migrant birds BUEHLER, D. M*; TIELEMAN, B. I.; PIERSMA, T.; Univ. of Groningen; Univ. of Groningen; Univ. of Groningen; Royal Netherlands Insitute for Sea Research d.m.buehler@rug.nl
How do migrating birds deal with disease threats and allocate resources needed for immune function over the annual cycle and in different environments? To find out, we studied red knots, a species of long distance migrating shorebird. We measured immune function once a month for a year in knots living in captivity. We also manipulated air temperature to see whether increased energy expenditure (spending energy on staying warm) affected immune function. In a separate experiment, we manipulated food availability to see whether decreased energy intake affected immune function. We used assays for measuring different aspects of constitutive immune function from a single blood sample, and in the food availability experiment we also induced an acute phase response. We then used multivariate statistical techniques to examine whether different aspects of immune function group together into strategies. We found that immune function varied significantly over the annual cycle, even in captive birds. Furthermore, covariation between immune indices suggested that birds use different immune strategies during different annual cycle stages. Strategies based on phagocytosis increased during spring migration, but decreased during peak feather molt. We also found that neither increased energy expenditure nor decreased food availability affected constitutive immune function. However, aspects of the acute phase response were adjusted in birds experiencing limited access to food. Thus, constitutive immunity persists under conditions that challenge energy balance while birds save energy on more costly aspects of immunity. Based on these findings we conclude that some immune strategies may be more costly than others and should be used only when their benefits outweigh their costs.
