Age-related differences in body condition during fall migration in response to pedestrian activity

Successful stopovers are critical to the survival of migratory landbirds. As the environment becomes increasingly urbanized, understanding the role urban greenspaces play as stopover sites becomes more and more important. One potential detriment migrants may face in these urban stopovers is pedestrian activity. A migrant may not be able to accumulate sufficient fat stores if it is repeatedly being flushed by passing pedestrians or if it is having to be more vigilant of pedestrians as potential predators. Using a body condition index, we compared body condition of birds in areas of different pedestrian activity during fall migration. Overall, HY birds were in better condition in the less intruded site, whereas AHY birds showed no difference. When comparing migrants versus residents, migrants were in better condition away from pedestrian activity, regardless of age. Residents, regardless of age, showed no differences. These results suggest that HY birds in general are more sensitive to pedestrian activity, and that migratory species may require a longer stopover to accumulate sufficient energy stores so as to resume migration.