Flight characteristics of non-migrating and migrating populations of turkey vultures

David Patrick Arrington, Purdue University

Abstract

Flight altitude characteristics of non-migrating turkey vultures (Cathartes aura) were examined in Indiana and Ohio for future incorporation into aircraft/bird avoidance models. Vultures spent 74.3% of the day perched and 25.7% in flight. Of time in flight, 97.4% was at or below 151m (500 ft) above ground level (AGL), corroborating previous studies suggesting these birds fly primarily at low altitudes for foraging efficiency and energy conservation, even when available dynamic lift would allow flight at much higher altitudes. There was no significant difference in altitude band selection among 3 sites separated by >200km, demonstrating that altitude modeling is possible. Correlating weather variables with altitude selection proved difficult; regression analysis yielded mixed results, forcing a simplistic altitude model concept. Turkey vultures do not move randomly across the landscape, but remain within annual home ranges that target specific habitat types. Average home range size for 3 separate populations from 1996–1998 ranged from 149km 2 at NPBRS (Ohio site) to 627km2 at CNSWC (south-central Indiana site); associated embedded 90% Kernel values for the same locations were 20km2 and 170km2. Turkey vultures spent 77.7% of the day perched in or flying over wooded habitat and spent much less time in other available habitats—agriculture (15.4%), landfills (6.1%), urban (0.6%) and wetlands (0.1%). Observations, averaged for each site, showed that the majority of movements within home ranges were within 15km of the primary roost—NPBRS (99%), PRFWA (97%), and CNSWC (92%). Data demonstrated that turkey vulture movements around primary roost sites could be modeled for inclusion into existing U.S. Air Force bird avoidance procedures. However, identification of primary roost sites within boundaries of low-level flight corridors is necessary to complete this task. Satellite data were collected on 2 turkey vultures (1 immature and 1 adult) captured at the National Plum Brook Research Station, Ohio. Two additional birds tagged at Pigeon River Fish and Wildlife Area failed to provide data. The immature bird provided 107 locations and 7 migration movements; 5 of the 7 movements (71%) were associated with a weather-front passage. The bird migrated 289km southwest, and settled in spring in an area 211 km south of the initial trapping location. The mature bird provided 93 locations and 15 migration movements; 12 of the 15 movements (80%) were associated with a weather-front passage. The bird migrated 1287km southeast and returned to the trapping area <3 months later. The flight altitude and habitat association data on these birds proved unreliable. In order to attain critical flight altitude and habitat preference>data, future bird avoidance research of migrating turkey vultures should utilize global positioning systems.

Degree

Ph.D.

Advisors

Weeks, Purdue University.

Subject Area

Forestry|Ecology

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