FLIGHT BEHAVIOR OF BLACK AND TURKEY VULTURES: IMPLICATIONS FOR REDUCING BIRD–AIRCRAFT COLLISIONS

摘要

Mid-air collisions with black vultures (Coragyps atratus) and turkey vultures (Cathartes aura) regularly cause substantial damage to military and civilian aircraft. Information concerning the flight behavior of black and turkey vultures potentially could improve predictive models designed to reduce bird strikes by aircraft. We examined the flight behavior of black and turkey vultures at the Savannah River Site (SRS) in South Carolina, USA, and determined whether flight characteristics were predictable with respect to weather and time variables. We captured birds at their primary roost and subsequently relocated them via aerial telemetry from 11 February 2002 through 29 January 2003. One hundred eighty of 326 locations (55%) for 8 black vultures and 129 of 206 locations (63%) for 5 turkey vultures were of flying birds. Black vultures flew at an average altitude of 169 ± 115 (SD) m above ground level, whereas turkey vulture flight altitude averaged 163 ± 92 m. Our results contrast with those of previous studies that reported less frequent and lower altitude flights. The flight behavior of both species appeared to be influenced minimally by weather and time variables. However, we were unable to construct useful models predicting aspects of flight behavior using the variables we measured (all models had R2 or pseudo R2 values <0.10). We suggest that other factors, such as food availability, inter- and intra-specific interactions, and physiological demands play a larger role in vulture flight behavior than the variables we measured. Our results suggest that the development of bird avoidance strategies by aircraft operators should consider the variability of flight behaviors of black and turkey vultures across their ranges. Future research emphases should shift from examinations of the effects of local conditions on flight behavior to the elucidation of factors contributing to differences in flight behavior among regions.