| I studied endogenous versus environmental control, biogeography, and hazard to aircraft of the migrations of North American breeding raptors. Based on species differences in annual consistancy of migration timing, migrant raptors most closely associated with the tropics during the non-breeding season are the most reliant on endogenous control of migration, while species confined to the temperate zone throughout the year are more reliant on environmental control. Degree of migratory behavior was found not to be correlated with diversity, based on number of subspecies, when considering Falconiformes and Strigiformes together or when considering Falconiformes alone. A strong negative correlation (r = -.92) was found between migratory behavior and diversity in Strigiformes. The recent history of glaciation and arrival of extreme climate zonation indicate the comparatively recent nature of raptor migration routes. Hazard to aircraft created by migrating raptors can be minimized by avoiding concentration locations and altitudes at the appropriate times. |
