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Martell, M., C. Gieck, J. Nibe, D. Erickson, B. Mandernack, and P. T. Redig. 1991. Bald eagle winter roosts on the Mississippi and Wisconsin rivers. Report submitted to the Minnesota Department of Natural Resources. 42 pp.
During the winter Bald Eagles (Haliaeetus leucocephalus) congregate near open water by day searching for food which includes fish, waterfowl, and carrion. Eagles have also been reported feeding at inland sites, usually where there is a livestock farming operation. During the evening they congregate at communal roosts which are often used every night. These roosts are though to provide protection from winds, precipitation, and cold temperatures. The importance of both the winter feeding areas and evening roosts to Bald Eagle populations has been recognized for many years and was considered critical in their recovery by the Northern states Bald Eagle Recovery Team.
Bald Eagles use both the Mississippi and Wisconsin rivers and their tributaries for foraging, rest sites, and evening roosts. Bald Eagle use of the rivers is threatened however from habitat loss due to residential and commercial development, increased recreational activities, and contamination of the eagles prey.
Specific locations of Bald Eagle roost and feeding sites along the Wisconsin portions of the Mississippi and Wisconsin rivers has been poorly documented, and little is known about the numbers of birds, their ages, or seasonal movements. We report here on a project to document eagle use of these rivers.
During the winter of 1990-91 we attempted to locate and document roosting sites of Bald Eagles wintering along portions of the Mississippi and Wisconsin rivers. This was done through a literature search for known roosting and feeding sites, and ground searches to locate Bald Eagle roosting areas. We also documented the numbers and ages of eagles using these areas, and attempted to identify factors such as weather and human use patterns which might affect eagle use and impact the management of the area.