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Tenney, M.K. 1986. A life history study of turkey vultures along the root river valley in Fillmore county, Minnesota. Final report submitted to the Minnesota Department of Natural Resources. 76 pp.
The Turkey Vulture (Cathartes aura) is the only member of Cathartidae to occur in Minnesota. Little information regarding population size, nest and roost location and usage, roost site habitat requirements, and foraging ranges for Minnesota Turkey Vultures is extant. The purpose of this study is: to increase information (baseline information) regarding Cathartes aura on population size, nest and roost location, nest and roost usage, roost site habitat requirements, and foraging ranges. Specific objectives include: 1) to locate all nest and roost sites within the Root River Valley of Fillmore County, 2) to determine habitat requirements associated with roost sites, 3) to estimate the foraging ranges of vultures roosting in the study area, 4) to describe nest sites and nestling development in the study area, and 5) to determine roost usage within the study area.
Six trap sites were established. Bait consisted of road killed wild animals collected under a Minnesota Department of Natural Resources Special Permit and dead domestic livestock was obtained at an area rendering plant. Capture techniques included a noose carpet and a rocket net. Trap sites were established and baited no less than 2 weeks prior to capture attempts in an effort to establish habitual and consistent visits by area vultures. All captured vultures were fitted with vinyl wrap-around patagial streamers following Sweeney (1984). Turkey vultures were captured at 3 of the 6 trap sites used during the study. Successful sites afforded feeding vultures an unobstructed view in at least 2 directions and had no less than 1 large dead tree nearby allowing perched vultures to view the carcasses. All bait site capture attempts were accomplished using a rocket net, averaging 2.8 vultures per capture attempt. A wide range of 12,840 ha to 11,750 ha was observed in foraging ranges. Important Turkey vulture roost characteristics as determined by study were: large DBH and height combination, an average of twice as tall as non-roost trees within a 0.04 ha circular plot centered at roost tree, several suitable trees within 10.5 m of one another, close proximity to water and clearing, large distance (> 500 m) to a human activity area, large stout horizontal tree limbs, dense canopy in cold weather.