Follow Your Elders: Age-related Differences in the Migration Behavior of Broad-winged Hawks at Hawk Mountain Sanctuary, Pennsylvania

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Abstract
We studied the flocking behavior of adult and juvenile Broad-winged Hawks (Buteo platypterus) migrating past Hawk Mountain Sanctuary in eastern Pennsylvania during September 1996 and 1997. Adults were more likely than juveniles to fly in flocks (78% versus 62%). All-juvenile flocks had a mean of 2.0 (±0.0) birds, all-adult flocks a mean of 4.5 (;pm0.4) birds, and mixed-age flocks had a mean of 4.7 (;pm0.4) birds. Adults, which made up 68% of all individuals in mixed-age flocks, were the first or “lead” birds in 80% of these flocks. Most (58%) adults migrated in the first, or leading, half of such flocks, and most (68%) juveniles migrated in the trailing half. Overall, our results suggest that migrating juvenile Broad-winged Hawks are more likely to follow adults than vice versa. Following experienced adults may help juveniles in two ways, first by allowing them to find thermals more quickly, and second by enabling them to better navigate to appropriate wintering areas.