Double-crested Cormorants (Phalacrocorax auritus) breeding in the Great Lakes and wintering in the southeastern United States were implanted with satellite transmitters to assess their movements. During 2007 and 2008, 26 cormorants from Georgian Bay, Ontario, Canada, were tracked in order to, variously, identify staging areas, characterize migration routes, winter habitat use, and home range size, assess philopatry of returning breeders, and test for a relationship between winter habitat use and arrival at the breeding ground. Females left summer areas earlier and spent more time in staging areas than did males. However, both sexes left the staging areas and arrived in the wintering grounds at approximately the same time. There was no difference in latitude between wintering males and females, or in winter residency time (n = 136 days for both sexes). The predominant winter habitat types were lakes and coasts with only seven of 26 (26.9%) birds wintering on aquaculture sites. Contrary to expectations, winter home ranges of birds on aquaculture sites ( = 2760 km2) were significantly larger than birds on non-aquaculture sites ( = 81 km2). A carryover effect of aquaculture was not detected; winter residency time was similar for birds on both aquaculture and natural winter habitats, with birds from both habitats returning north at the same time. Fidelity to the previous summer's location was observed in 15 of 20 returning individuals.
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Vol. 33 • No. 4