Bald eagles or Haliaeetus leucocephalus are the national symbol of the USA, so chosen because of the species’ uniqueness to North America. However, the history and existence of this regal creature has seen many ups and downs as efforts have been made to protect and conserve it. While initially, bald eagles were found in all 50 states, gradually trends were seen that proved otherwise. Hunting, trapping and development were decreasing the numbers of this glorious bird. In addition, the 20th century brought in other threats to the bald eagle. Chemicals and pesticides, such as DDT, were responsible for reducing the numbers of the bald eagles to a worrying degree. According to the Smithsonian National Zoological Park, “At their lowest point, only 420 nesting pairs of bald eagle could be found in the continental United States.”
When the dangers of DDT and the damaging effects of hunting and habitat destruction were highlighted, laws were enacted to protect and conserve these birds. In 1972, the law that banned the use of DDT set in process the road to recovery for the bald eagle. Moreover, bald eagles were one of the first to be declared endangered under the Endangered Species Act of 1973. Comprehensive measures were taken to protect the habitat of the bald eagle, including providing them with clean water and turning important nesting areas into National Wildlife Refuges. These measures had a degree of success and the Smithsonian National Zoological Park reports that today there are more than 6,000 pairs of these beautiful birds in the continental U.S. However, there is still some way to go, as the University of Wisconsin, Sea Grant states that populations in the lower 48 states is still low and a large number of birds still show pesticide residue in their systems.
The bald eagle is one of the largest raptors or birds of prey and has two sub-species: the northern bald eagle or Haliaeetus leucocephalus alascanus, and the southern bald eagle or Haliaeetus leucocephalus leucocephalus. According to Steve Potts and Sigrid Noll- Ueblacher, northern bald eagles live in the north and migrate to warmer areas during the winters while southern bald eagles live in the warm southern states and do not migrate.
According to the California Nature Mapping program, “The Bald Eagle is found only in North America, primarily in coastal areas or near large inland lakes and rivers that have abundant fish.” The Department of Environmental Protection, Connecticut describes the range of the bald eagle as, “The bald eagle nests from Alaska and Newfoundland south to Baja California, the Gulf Coast and Florida. The greatest concentrations of wintering bald eagles are found from November to March in the western and midwestern United States. Smaller concentrations of wintering eagles are also found in New England during this same time period.”
The size of the bald eagle can vary, according to its age, gender and area of habitat. Female bald eagles are larger than their male counterpart. According to Karen Dudley in Bald Eagles, “Female bald eagles have a wingspan of 7.5 feet (2.3 m). Males have a wingspan of only 6 feet (1.8m).” Even their weight differs drastically with the female weighing at an average of 10 to 14 pounds and the male weighing far less at 8 to 10.5 pounds.
Vision is, according to Dudley, the bald eagle’s most important sense. It allows this bird of prey to sight its kills from a distance and according to Dudley, bald eagles also have the best color vision of all animals. In fact, she writes, “The resolution or clarity of a bald eagle’s vision is exceptional, even better than color vision. Eagles can see up to three times more clearly than humans.”
Bald eagles have strong, yellow-colored feet that are unfeathered and have rough undersides that allow the eagles to hold onto their prey. They have four toes, on the tips of which they have their most deadly weapons – talons. The talons are sharp and powerful.
Bald eagles have no teeth and they swallow their food in pieces, after tearing up the prey into bite-sized pieces.
Dudley also describes the plumage or covering of feathers of the bald eagle as truly unique. She writes, “An adult bald eagle has a bright white head and tail that stand out against its dark brown body. An immature bald eagle’s plumage is a speckled combination of brown, tan, gray, black and white.”
According to the California Nature Mapping program, bald eagles have been known to survive in the wild for 30 years or more. However, in captivity, they have been known to survive for nearly 50 years.
Bald eagles mate for life and adult eagles remain busy with nesting in the spring and summer seasons. They also tend to stay near their nesting localities if they can get adequate food and can bear the weather. Northern bald eagles tend to winter in southern states for food and tolerable weather. While adult bald eagles may tend to winter in the same areas over and over again, they do keep moving around, hunting and looking for prey. A lower activity level during the winter months helps these birds to conserve their energy.
Dudley also describes the winter roosting of bald eagles. Roosts are basically perching trees of the eagles. The birds may roost together and quite often the same sites are used each year. Roosting sites can be quite noisy since, “If one eagle lands too close to another, the perched eagle will hiss and threaten the newcomer.” The birds generally arrive at the communal roosting site towards the close of daylight.
While fish forms the main diet of bald eagles, they also hunt and eat other prey. According to the Alaska Department of Fish and Game, eagles also prey upon sea urchins, crabs, clams, waterfowl, carrion, and small mammals. Eagles often snatch away food from smaller animals and birds. They kill their prey by grasping it with their strong, sharp talons and usually carry smaller prey in flight.
In extreme winter and cold weather, eagles hunt for other sources of food, including smaller birds and mammals. They may also migrate to warmer climates if shortage of food and prey persists.
Bald eagles often build their nests close to water bodies for easy access to food. They also tend to nest in the same place each year. They look for relatively large water bodies, such as, rivers, lakes and reservoirs. Nests are made in large, tall trees that are free of any disturbance and would protect them from the winter harshness while providing a place to roost.
The main factors that affect the mortality of the bald eagle and limit its growth mainly include pesticides and chemicals. According to Texas Parks and Wildlife, use of insecticides such as DDT and Dieldren were responsible for the dramatic decline in the bald eagle population. While DDT caused damage to reproduction, causing birds to fail laying eggs, lay eggs with dead embryos or with extremely thin shells, Dieldren simply killed the eagles.
Lead poisoning is another important cause of decline of the bald eagle population. By feeding on waterfowl shot with lead pellets, eagles accumulate harmful levels of lead in their bodies. Not only that, eagles have also died due to ingesting the lead pellets after feeding on dead or injured waterfowl.
Another reason for the decline in their numbers is the destruction of natural habitats. “Unfortunately for eagles, people also like to live and spend their leisure time near water. In recent decades, the accelerated pace of development along the coast and near inland rivers and waterways is a primary cause of habitat loss.” [Texas Parks and Wildlife] Changes in land use and activities that have a negative impact on the nesting and roosting habitats of bald eagles result in reducing their numbers.
While shooting of bald eagles has been illegal since 1953, this does remain a limiting factor since people continue to hunt the bald eagle and shoot it down. Other limiting factors include, reduction or alteration of river flows, electrocution through power lines and human disturbances to the natural habitats.
Management and Outlook
Consistent and determined efforts by state and national government and private agencies have ensured that the bald eagle is protected and can thrive in safe habitats. Habitats and roosting sites have been identified and kept ‘safe’ for the bald eagle. In addition, measures have been taken to ensure that river flows and water bodies that provide food to the birds are protected at all costs and efforts have been made to improve the water quality. .
Biologists and organizations have undertaken intensive monitoring of bald eagle nest-building activities and also, enabled building of disturbance-free zones to facilitate peaceful and productive nesting. Owners of land tracts and developers have also been advised to engage in protecting the habitat of the bald eagle.
Deaths and illnesses of the bald eagles are investigated to examine causes and identify any illegal reasons for death. Overall, while the bald eagle population has responded positively to the ban on DDT and organochlorine pesticides, this particular limiting factor does remain the number one reason to adversely affect the birds.
It is important to continue to keep a close watch on the numbers and conditions of the bald eagles in order to ensure that they not only survive but also thrive. Moreover, close monitoring will ensure nipping new limiting factors in the bud.
Across the United States, the numbers for the bald eagle look promising. According to the U.S Fish and Wildlife Service, the number of nesting bald eagle pairs and productivity have been monitored since the species was listed as ‘endangered’. According to a news release, dated May 14, 2007, by the USFWS, “Bald eagles in the lower 48 states have climbed from an all-time low of 417 nesting pairs in 1963 to an estimated new high of 9,789 breeding pairs today.”
While the outlook does seem promising and positive for the bald eagle, efforts are still on to ensure that the species will continue to be safe, protected and productive. The path is difficult but the thrill of seeing the regal, splendid bird soar high and swoop low makes the journey and the hurdles all truly worthwhile.
Here are some useful resources to learn more about the life, history, habitat and other interesting features of the bald eagles.
- Bald Eagle Facts – Detailed information on the features, distribution and behavior of the bald eagles.
- The Call of the Bald Eagle – Listen to the call or sound of the bald eagle. Also, includes useful information on life history and identification.
- Bald Eagle Pictures – Lots of pictures and images of the bald eagle. Also, find details on classification and general information regarding this regal bird.
- About the Bald Eagle – Helpful and detailed information on the bald eagle, complete with pictures, links to sounds and videos of bald eagles building nests, incubating eggs as well as information on their preys and predators.
- Conservation Measures for Bald Eagles – Useful information on conservation measures taken to protect the bald eagles. Also, includes details on significance, features and habitat of the eagles.
- Everything About Bald Eagles – Comprehensive and useful information on the bald eagle’s identification, life history, BBS and CBC maps and taxonomy.
- Interesting Bald Eagle Facts – Unique and interesting information about bald eagles. Also includes background, habitat, diet and description as well as information on how one can help to protect them.
- Population Details of Bald Eagles – Helpful details on the population of the bald eagle in different parts of the U.S.
- Bald Eagle Information for Kids – Learn about why the bald eagle was chosen as the national symbol.
- Laws Protecting Bald Eagles – Everything about the laws that exist to protect the bald eagle.
- Facts about the Bald Eagle – Helpful details on the history, distribution, habitat and status of the bald eagle. Also, includes information on projects relating to their restoration and research.