By Susan Thurn,
Cable Natural History Museum
They have a seven-foot wingspan. They can fly average speeds of 30 miles per hour. They are amazing predators in the sky. They are incredibly beautiful. They are America’s symbol. They are the bald eagle, and they are something that most humans never tire of observing.
Saturday evening I was at a Cable community event, and several people asked if I’d seen the eagles near the Namekagon River on County Highway M. My family and I saw four of them, although others shared that they had seen ten earlier in the day. The excitement was shared by all of the observers.
Research has shown that bald eagles in the Great Lakes area don’t usually migrate. Our northern eagles fly far enough south to find open water with sufficient food supply. An eagle can travel up to 100 miles on a winter day to find food.
The week of March 22, 2011 brought a huge number of migrating eagles back along the Mississippi River, a place not too far away from us as the “crow” flies. The bald eagle can fly hundreds of miles in just a few days. They migrate in large groups, streaming along in a path that can be up to thirty miles long with over a half-mile width. Daylight is the cue to migrate rather than weather, so eagles can migrate north to their home range to find that winter is still present. Then they cope with food availability, often depending on road kill for their meals if open water is not an option.
Bubbles of rising, warmed air, called thermals, are what aids eagles in migration. They glide on these thermals in the desired direction until they find another. This method of flight allows them to conserve energy.
Eagles are diurnal (daytime) fliers, and probably use landmarks to guide them to a home territory, while using more specific cues to find their nest tree. Clearly their memories must be great, showing a high level of intelligence.
Immature bald eagles will often wander back to their birth territory in the spring, but do not always stay put. Usually around age five, when they reach sexual maturity, they will establish nesting sites within 300 miles of their birthplace.
Living among some of the greatest bald eagle habitat, we are fortunate to be able to see bald eagles almost daily. They are an integral part of our ecosystem, one that is worth taking great care of, here in our own back yards.
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Also discover us on Facebook, or at our blogspot, http://cablemuseumnaturewatch.blogspot.com/ to learn more about our exhibits and programs.