BY CLAY STEELE
(Photo courtesy of the Iowa Department of Natural Resources)
IF YOU SPEND ANY AMOUNT of time along the Iowa River, you should expect to see an occasional Bald Eagle. Find yourself at the Mississippi, however, and expect to see hundreds—at least if you’re at Lock and Dam 19 in Keokuk during Iowa’s colder months.
For 19 years people have been coming to Bald Eagle Days in this river town to view the 400 to 700 eagles that migrate south to spend the winter in this area. At a time when their northern fishing areas are freezing over, the Bald Eagles are attracted by the abundance of food and roosting sites provided by the lack of ice below the dam and the ample stands of large cottonwood and sycamore trees on the eastern bank.
There was a time, however, when few Bald Eagles were seen along Iowa’s waterways. Although small numbers migrated through, none nested in Iowa from approximately 1900 to 1977. When white settlers arrived in Iowa in the 1830s Bald Eagles were common, but they were nearly exterminated after 60 years of habitat loss, sports hunting, and persecution by farmers who killed them because they believed they would eat their chickens and young animals.
In 1940 a law was passed to protect the birds from hunting, but the next couple of decades brought with them the knowledge that something even more menacing was continuing to imperil the Bald Eagle—DDT. Widely sprayed throughout the U.S. to control insects, DDT was found to interfere with calcium metabolism in birds, causing the shells of the eggs they laid to be very weak. The weight of the adult Bald Eagle as it attempted to sit on the egg caused it to collapse. It was almost too late when DDT was finally prohibited in the U.S. in 1972.
Once considered endangered in most of the lower 48 states, Haliaeetus leucocephalus, the Bald Eagle, has made a remarkable recovery since DDT was banned. Only 84 eagle nests were counted in 1998, 43 in 1995, and barely more than a dozen in the early 1990s. Since then, eagle nests have been reported in 86 of Iowa’s 99 counties, and over 9,000 nesting pairs were counted in 2006! Each year up to 7,000 bald eagles gather along the Mississippi River to winter over.
The main threats to the Bald Eagle today are still human related. People continue to kill them, for sport or out of ignorance. They fly into electric wires, or get hit by automobiles. They die from contaminants and poisoned bait set out for other animals. The most harm by far, though, is through loss of habitat—places to breed, rest, and feed away from human disturbance. The lack of the tall open-crowned trees required to accommodate the huge wingspan of these raptors limits the areas in which they can nest and roost. Their favorite tree, the white pine, was almost entirely logged out of the state a century ago. Roads and development now criss-cross through ideal Bald Eagle habitat, affecting these birds’ ability to nest away from disruption.
Like most animals, Bald Eagles are complex creatures with specific needs. A member of the genus Haliaeetus, it is also known as a Sea Eagle, a type of eagle that hunts primarily for fish. The Bald Eagle is, surprisingly, not closely related to the other North American eagle, the Golden, a markedly different species that feeds on land animals and birds and is more closely related to hawks than to Sea Eagles. As implied by its genus name, the Bald Eagle spends a great deal of time around water, but will also venturefar out over land. A powerful hunter, it is an equally opportunistic scavenger. Preferring fish, but eating waterfowl and mammals if necessary, the Bald will catch them, steal them, or obtain them already dead.
Bald Eagles can have a wingspan of seven feet, with the females being slightly larger than the males. They have finger-like feathers on the end of their wings and have the familiar, distinctive markings of a white head and tail. Juveniles are mottled brown and lack the white coloring of the adults, and are thus often confused with Golden Eagles, which are rarely seen in Iowa, or with Turkey Vultures, summer residents who have already migrated by the time the Bald Eagles have arrived. A Bald Eagle retains its juvenile markings for up to five years.
Bald Eagles often form life-long breeding pairs and frequently use nests for many years. Built high in a very large tree, the nest is made of sticks and is added to with each season’s use. The Iowa Breeding Birds Atlas reports that these nests can reach 7 feet across, 12 feet deep, and weigh 2 tons. With a good windstorm, the sheer mass of a Bald Eagle nest has been known to topple the tree it sits in. An average of two white eggs are laid and both the male and female incubate them for just over a month. Both parents also feed the young, with one guarding the nest at all times. After two and a half to three months the young can fly, but may stay near the parents for another couple of months until their hunting skills are perfected.
Once they leave the nest, Bald Eagles are solitary creatures, coming together only when feeding at sections of open water and high fish concentrations, or to breed. If you get the opportunity to view them, take it. Remember, your grandparents, your great-grandparents, and even their parents probably did not. And if it weren’t for the efforts of a dedicated few, your grandchildren probably wouldn’t get to either. Let’s learn the lessons the Bald Eagle taught us about over-hunting, habitat loss, pesticides, and pollution, so those who follow us don’t have to hear sad tales of near-misses and those who didn’t make it. While we’re at it, maybe we can think about how it affects us, too.
For more information on eagle watching in Keokuk, call (800) 383-1219.
Clay Steele is an AmeriCorps Naturalist with the Johnson County Conservation Board. Reach him at (319) 645-2315.