Meeting Abstract
Seasonal migration and natal dispersal represent the major large-scale movements in the lives of many animals. Individuals that are more prone to movement might both disperse and migrate farther distances. Such behavior may increase encounter rates with parasites and diversity of parasites encountered. Alternatively, parasitism may prevent individuals from migrating long distances, potentially resulting in a negative relationship between infection and movement. We examined whether natal dispersal tendency predicts seasonal migration distance in song sparrows (Melospiza melodia), and whether migration distance predicts haematozoan parasitism. Migration distance, inferred from stable-hydrogen isotope analysis (δ2H) of tissue grown on the wintering grounds, varied consistently among individuals over years, and was greater in females than males. Migration distance varied with natal dispersal, as inferred from genetic assignment tests: birds that had immigrated from farther outside the study area also overwintered farther south from the breeding grounds. Among after-second-year birds, but not in yearlings, longer-distance migrants were more likely to be infected with haematozoa. Individuals that travel long distances in the context of natal dispersal also appear to travel long distances in the context of seasonal migration, supporting the possibility of a behavioral syndrome with respect to movement in this species. The degree to which individuals move across the landscape may influence their exposure to infectious disease, particularly in adulthood once immune repertoires are relatively crystallized.
