The pair of Bald Eagles has returned to their nest in Mooseheart, Illinois, only a mile from our second home. They raised and fledged three eaglets last season. They are about 3 months later than the Pembroke pines eagles in their breeding milestones, so they are not expected to lay eggs until late March or early April. They will spend the winter here as long as the rivers and larger lakes are not ice-covered. Many other eagles come down here during the winter-- hundreds along the Fox River near their nest.
As is the case with the Pembroke Pines pair in Broward County, these are the very first pair known to nest in Kane County in 50 years or more. I took these photos this morning.
Kelly asked about the locally-nesting eagles here in NE Illinois. Yes, these tend to stay in the area or move south along the river system depending upon the severity of the winter. A very timely question, as I had been planning to write a blog on this subject.
Bald Eagles have complicated migration habits, differing by age of the birds, geographic location and the effects of weather and climate. Their dependence upon fish as a dietary staple figures in on their seasonal movements, as open water is essential and cooler water more desirable, especially for younger birds as it causes the fish to move nearer the surface, making them easier to catch. Adults seem to want to stay around and defend their territory during the non-breeding season while young birds travel more widely.
Northernmost Bald Eagles such as those in northern Canada typically fly south during the winter, with juveniles and immature birds leading the exodus. They congregate in coastal areas or large rivers and lakes that are not iced over. In the Northwest, the timing of the salmon run influences post-breeding movement, as many move northward and northwest in late summer, join Alaskan birds following the spawning salmon southward along the coast, then linger through the relatively mild winters along the Pacific coast.
Bald Eagles from the North Central states such as those at our local nest in NE Illinois will wander locally as conditions permit. When winter sets in, eagles from the north join them, especially at dams and locks along the Illinois and Mississippi Rivers. While Illinois has only about 30-40 breeding pairs of Bald Eagles, the state's winter population is commonly over 3000 individuals from December through March.
In the Northeast US, Bald Eagles fly south in fall (August through December) along the Appalachian mountains or follow the Atlantic coast. Many congregate in Chesapeake Bay, and are joined by migrants, mostly immature birds from more southerly locations. Some Florida immature eagles have been tracked as far north as New England, returning to Florida in October-December. Adult Bald Eagles in south Florida tend to wander in the vicinity of the nesting territory during the non-breeding season (July through September).
Generally, Bald Eagles that nest in the lower 1/3 of the US (below 40 degrees latitude) are said to have less north-south migratory movement.