Effects of Migration Schedules on Physiological Condition and Timing of Breeding in Wood Thrush (Hylocichla mustelina)

I examine for the first time whether individual migration strategy affects physiological condition upon arrival and how arrival condition influences reproductive effort in a migratory songbird. Migration duration was predicted by departure date from the wintering grounds, arrival date to the northern Gulf coast, and arrival date to breeding grounds using geolocators, but not by sex (n=15 males, 6 females). There was a significant negative relationship between the number of days spent on migration and arrival mass index in males (p=0.027), with B-OH concentrations (p=0.013), and a positive correlation with baseline CORT (p=0.0026). High baseline CORT was significantly correlated with later mate acquisition dates for males (p<0.001). Arrival date predicted first egg date (p=0.012). Males had significantly higher adrenocortical responses and differences between adrenocortical responses and baseline CORT than females. My study suggests that migration behaviour could have carry-over effects of poor stopover habitat on arrival condition and reproductive success.