Flapping rates of migrating and foraging Turkey Vultures Cathartes aura in Costa Rica

Abstract

Local and migrating populations of Turkey Vultures Cathartes aura co-exist in Costa Rica in autumn and spring (Stiles & Skutch 1989). We studied the flapping rates of individuals from these two populations to compare flight modes and the amount of energy invested in active flight. Migrants tended to fly higher in more stable air than local birds, which often fly low over the forest canopy while searching for carrion. Overall, migrants flapped at lower rates than did local, non-migratory birds. Migrants, but not local birds, flapped more on cloudy days than on sunny days, and more at the start and end of the day than at mid-day.