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Abstract -
Haliaeetus leucocephalus (Bald Eagle) is an adaptable predatory bird that commonly captures live prey, but regularly scavenges. Large mammalian prey (e.g., Odocoileus virginianus [White-tailed Deer]) have been observed in Bald Eagle diets, but were considered scavenged. To our knowledge, Bald Eagle predation of a live ungulate has only been reported once, and occurred in Menominee County, MI. In June 2009, we captured and radiocollared a female White-tailed Deer fawn (2.7 kg) in the south-central Upper Peninsula of Michigan. The fawn was last radiolocated alive 8 h after release in a short-height (20-30 cm) grassland field along a river approximately 570 m from an eagle nest. Estimated time of mortality of the fawn was 10 h post release. Approximately 27 h post release, 2 legs, >50% fawn hide, and the radiocollar were present in the nest along with 2 eagle nestlings (estimated age 9-10 wks). We believe this was a possible predation event based on the 8-h period between fawn relocations, fawn movement, foraging behavior of the nesting eagles, and presence of the carcass remains and radiocollar in the nest.
Introduction
Haliaeetus leucocephalus L. (Bald Eagle) has evolved life-history strategies that include great diet plasticity. Bald Eagles commonly capture live prey, but scavenging is regularly observed (Elliott et al. 2006, Isaacs et al. 1996, Lang et al. 2001). Bald Eagle diet varies with season and geographic region (e.g., Isaacs et al. 1996, Jackman et al. 1999) and primarily includes fish (e.g., Kozie and Anderson 1991, Lang et al. 2001), but also birds (Morris 2002, Ricca et al. 2004), reptiles (Means and Harvey 1999), invertebrates (Jackman et al. 1999, Murie 1940), and mammals (Isaacs et al. 1996, Kozie and Anderson 1991). Medium-sized mammals reported in their diet include hare and rabbit (Family Leporidae; Dominguez et al. 2003, Hunt et al. 2002, Kozie and Anderson 1991), Enhydra lutris L. (Sea Otter; Anthony et al. 1999, Ricca et al. 2004), Alopex lagopus L. (Arctic Fox; Anthony et al. 2008, Murie 1940), and Procyon lotor L. (Raccoon; Lang et al. 2001). Additionally Odocoileus virginianus Zimmermann (White-tailed Deer) (Kozie and Anderson 1991, Lang et al. 2001), O. hemionus Rafinesque (Mule Deer; Isaacs et al. 1996), Cervus elaphus L. (Elk; Isaacs et al. 1996), Rangifer tarandus L. (Caribou; Anthony...