Recovery of bald eagle numbers has been especially pronounced in the Midwest. Since 1985, several hundred nesting pairs of bald eagles in Minnesota, Wisconsin, and Michigan have grown to approximately 1,800 nesting pairs by 1996. Prior to European settlement, Iowa, Illinois, and Missouri undoubtedly hosted hundreds of nesting bald eagles. Unfortunately, by the early 1900s, all nesting eagles in these states had been eliminated. It wasn’t until 1977 that Iowa again had an eagle nest. Since then, bald eagles have nested in 42 Iowa counties along 30 river systems. In 1998, there were 84 active Iowa bald eagle nests, 47 of which produced at least 82 youngsters. Illinois and Missouri also have many nesting bald eagles once again.
In these latter three states, winter is the best time to observe eagles. During the winter, numerous eagles from northern states and Canada migrate south to find food. The birds begin arriving in Iowa during September and become more numerous through January, depending on the harshness of the winter. By the mid-1980s approximately 1,500 eagles total wintered in Missouri, Illinois, and Iowa. By 1996, that number has escalated to nearly 5,700 wintering eagles, more than one-third of all bald eagles counted in the lower 48 states during winter. Usually, only 200 to 300 eagles winter in Minnesota and Wisconsin.
The highest concentration of eagles in the Midwest is along the Mississippi River. Approximately 2,500 to 4,000 bald eagles winter along the Mississippi between Minneapolis and 50 miles south of St. Louis. The Mississippi River is a popular wintering area for bald eagles because of abundant food and open water, particularly at locks and dams and power plants that keep the river from freezing. This provides the eagles with an area to hunt their primary food source--fish. Gizzard shad and other fish often are stunned as they pass through the gates of the dam. This creates an easy-to-catch source of food for eagles. At Keokuk, where these conditions exist, 100 to 400 bald eagles may winter in the area.
In addition to food, eagles need places to roost during the night and perch during the day. Bald eagles generally roost together in large mature trees surrounded by a buffer of smaller trees. Roosts are chosen by the eagles to provide protection from the weather and avoid disturbances. Roosts are also generally close to a source of food. Daytime perches are usually within 60 yards of the water’s edge. Large cottonwoods tend to be used most frequently, although the eagles will choose smaller trees that are closer to the water. On mild days eagles may be seen standing on the ice.