Bald Eagles

Historical Perspective
The Greek interpretation for the bald eagle’s scientific name (Haliaeetus leucocephalus) is sea eagle with white head. In colonial times bald meant white as well as hairless. Consequently, even though the bald eagle has a fully feathered head, it was called bald because of its characteristic white markings.

The bald eagle is unique to North America. Unlike the golden eagle, which also lives in Europe, Asia and North Africa, the bald eagle only occurs from Florida to Alaska. Because of its native status and majestic appearance, the bald eagle was chosen by Congress as our national symbol in 1782. At that time, bald eagles were commonly seen in New England, particularly along the Atlantic coast. People could readily view the eagle hunting for its own food, occasionally feeding on carrion and pirating other eagles’ prey. Due to the bald eagle’s opportunistic scavenging, Benjamin Franklin was against the bald eagle as our national symbol and wanted the wild turkey instead.

Now the bald eagle is more commonly seen on flag posts, quarters, dollar bills and in photographs than it is in the wild. From the 1800s until recently, people frequently shot the bald eagle. Many people mistakenly believed eagles could carry away young children (they can only lift 3 to 5 pounds). Other people hunted eagles for their plumage or killed them because they occasionally preyed or scavenged on livestock.

European settlers relied heavily on wood products, and large scale timber removal resulted. This drastically altered and reduced the available habitat required by bald eagles. The introduction and widespread use of pesticides after World War II compounded the problem of reduced nesting sites, winter cover, and undisturbed food sources. Organocholorine pesticides, such as DDT and DDE, washed into our waters and entered the food chain. As these chemicals flowed up each level of the food chain from insects-to-minnows-to larger fish and waterfowl, the residual pesticide concentration in these animals increased. This made the bald eagles’ prey increasingly toxic to consume. By the 1960s, the bald eagle and its food sources were so contaminated that the chemicals interfered with the eagles ability to produce viable eggs. This reduction in reproduction, loss of habitat, and human persecution caused the near extinction of the bald eagle in the lower 48 states. Winter counts of bald eagles during the 1960s, averaged less than 4,000 eagles in the contiguous United States.

Good News
In 1972 DDT was banned in the United States. Then, in 1978 through the Endangered Species Act, the bald eagle was listed as endangered (in danger of extinction) in 43 of the lower states and threatened (likely to become endangered) in five others. This gave the bald eagle additional protection from human persecution and disturbance. It also created programs for the conservation of threatened and endangered animals and prohibited habitat destruction that would jeopardize the existence of any endangered species.

Protective laws and an increased awareness and concern for the bald eagle are leading to its recovery. The number of nesting pairs counted in the lower 48 states has gone from 417 in 1963 to 5,743 in 1998, a fourteen-fold increase! Because of this trend, on August 11, 1995, the bald eagle was officially reclassified from Endangered to Threatened status throughout the lower 48 states by the U.S. Fish and Wildlife Service.

Midwest Bald Eagles
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.

Eagle Etiquette
During the winter, bald eagles are under pressure to consume enough food and expend as little energy as possible in order to maintain body heat. If fishermen, bird watchers, or boaters get too close to the eagles, the birds will waste valuable energy flying away. It exposes them to undue stress and could cause abandonment of a site. To avoid disturbing eagles, do not get any closer than 400 yards from a perched eagle. If vegetation obscures the eagle’s view of you, still avoid getting closer than 100 yards. When possible, stay in your vehicle, use a blind, or stand behind stationary objects when viewing eagles. Stay on the opposite side of the river or lake to allow them a peaceful refuge. Since over 70 percent of the eagle’s feeding occurs during the early morning, avoid visiting areas that eagles rely on for food before 9 a.m. That will help to allow the eagle enough time to adequately feed before human activity disrupts their foraging.

If you find a dead or injured eagle, preserve the “potential” crime scene and call the local conservation officer, biologist, or US Fish and Wildlife Service office. Bald eagles are protected by four federal laws, with fines of over $20,000 for harassing, killing or wounding an eagle. If you see a bald eagle from April to August in Iowa, please report this to the local biologist or Wildlife Diversity personnel. An eagle seen during these months may be nesting nearby, and it is important to document any potential nest sites.

Eagle Profile
Bald eagles have a wingspan of 6 to 7 1/2 feet. The sexes are alike, with the female being slightly larger. Bald eagles sit 3 to 3 1/2 feet tall and weigh 8 to 15 pounds. Their eyes are 5 to 6 times more powerful than human’s. Their primary food is fish, and they will nearly always be seen near water. They also eat waterfowl, particularly the sick or injured, and occasionally carrion.

Bald eagles nest from November through April, depending on the latitude. It is believed that eagles mate for life. They frequently return to the same nest site year after year. The stick nests can reach sizes of over 7 feet across, 12 feet deep, and weigh over two tons. Nesting is a very critical time for bald eagles, so do not attempt to approach any nest.

The female lays one to three eggs. Incubation lasts 35-40 days, and the young’s first flight is about 75 days after hatching. Young bald eagles do not obtain the characteristic white head and tail of the adult until they are 4 to 5 years old. Until then, they can be identified in flight by a white diagonal strip under the wing and a spot in the “wingpit.” The belly, head, and tail will go through various mottled stages before reaching the adult markings. The white tail is generally the last adult characteristic to develop.

• Fact Sheet: Bald Eagles and Lead Poisoning,*.pdf