Eagle Nest


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The American Bald Eagle

The eagle had represented power and majesty for thousands of years before John Adams, Thomas Jefferson, and our Nation's other founding fathers chose the bald eagle as our national symbol in 1782. Then as now, the eagle represented 'a free spirit, high soaring and courageous.' Moreover, the bald eagle has always been uniquely American, found only on our continent. At the time the Republic was formed, the bald eagle was common in North America, soaring through the skies over its timber-bordered lakes, streams, and coastlines. Perhaps as many as 25,000 lived in what we now call the lower 48 states.

Today, except for the Southwestern bald eagles the bald eagle has been removed from the 'Threatened Species List in the United States.' Its number dropped dangerously low over the last century, for a number of reasons. However, the outlook is getting better. Because of the efforts of many people, the decline in the bald eagle population had apparently been halted and perhaps, was even reversed for a few years, but is now on the decline once more.

Conservationists view recent improvements with cautious optimism. But much work remains to be done - increased preservation of crucial natural habitat, greater public awareness of the eagle's problems, plus more public and private funding for conservation and research.

A major part of this effort lies in informing Americans about our National Symbol. A greater understanding and appreciation of this majestic, threatened bird will help it to survive and flourish as a valued part of our heritage.

Symbol Adopted
On June 20, 1782, the bald eagle was formally adopted as the emblem of the United States, a living symbol of our nation's strength and freedom. Today, the bald eagle represents more than a nation. The eagle typifies the plight of all wildlife struggling to survive in a world dominated by the needs of human beings. The decline of the bald eagle reflects the reduced quality of our natural environment. If this powerful symbol of freedom continues to be abused and neglected as it has been for decades, what hope does the future hold for less recognized species?

Concern for the fate of all endangered species is growing. At the same time, environment. Clear thought and keen awareness of these issues are essential, if we are to preserve unique and important ecosystems.

What is the Bald Eagle?
The bald eagle is a bird of prey - that is, a flesh - eating bird. Its Latin name - Haleaeetus leucocephalus - means 'white-headed sea eagle.' It is called 'bald' because the word was used in times past to mean white or white faced.

Field Marks:
Adult: dark brown body, white head and tail, yellow feet, beak and eyes. Immature: normally dark brown body, showing white in the wing linings and breast. It has brown head, tail, beak and eyes and is similar in appearance to the Golden Eagle without white on the tail. Golden Eagles have feathered legs to the toes. Bald eagles have bare legs.

Some immatures may have a white breast, a brown breast or a mottled breast.

A 4 yr old, or subadult, will be similar to an osprey with a whitish head with a line through the eye and a whitish tail with a black line along the end of the tail.

Found only in North America, the bald eagle is also called the American Eagle. The other eagle native to this continent, the somewhat less rare Golden Eagle, occurs in other parts of the world as well. The bald eagle is the North American continent's second largest bird of prey, surpassed in size only by the California Condor.

As is true with most birds of prey, the female is almost always larger than the male. A female bald eagle may stand as much as 107 centimeters (42 inches) high, with a wingspan of up to 240 centimeters (8 feet). Males stand up to 90 centimeters (35 inches) high, with wingspans of nearly 200 centimeters (6 1/2 feet). Body weights of bald eagles range from 3.6 to 6.4 kilograms (8 to 14 pounds), with females generally about a kilogram heavier than males.

How Do I know A Bald Eagle When I See One?
In addition to their large size, adult bald eagles are identified by their snowy white head and tail feathers. However, a young bald eagle does not get these white feathers until it reaches sexual maturity in its fourth or fifth year of life. Immature bald eagles are a mottled light and dark brown all over, and in flight they often are mistaken for golden eagles or turkey vultures.

Osprey are often mistaken for bald eagles, but with a little close observation can be easily identified. The osprey has a smaller head, that is white, with a black line going through the eye. Some 4 year old eagles will show this same black line, so the wing shape is the best identification. The osprey has a narrower wing than the bald eagle and normally has a crook in it, while the bald eagle wing will be straight.

What do Eagles Eat?
Sixty to ninety percent of a bald eagle's diet consists of fish. The birds generally scavenge dead fish, although they will catch live fish as well. They will take an occasional heron, crow, grouse, duck, gull, or small mammal, especially if fish are not available. They will feed on dead animals, if other food is not found. This includes dead animals, such as road killed raccoon or deer, as well as chickens and small pigs, which farmers may throw out with their manure during the winter. During deer season bald eagles may come down to feed on the innerds of the deer that the hunters leave behind.

The bald eagle is an opportunist and will sometimes steal fish from an osprey or crow. But ospreys have been observed stealing fish from young eagles as well. The bald eagle uses several fishing techniques. A favorite method is to perch in a tree and watch for a fish swimming in open water nearby, and then swoop down to capture it. If a suitable tree is not available near the water for perching, the birds may also fly out over open water looking for fish below. In winter, they may perch on the edge of ice near open water and wait for fish to float by, or to wash up on the ice.

After catching a fish the eagle will either fly back to a perching tree to eat it, or if the fish is small enough, swallow the fish whole while the bird is in flight. Occasionally, eagles will carry a larger fish they have caught back to the ice or to the shore to be eaten. In over 80% of their feeding, wintering bald eagles along the Mississippi River, feed upon small fish they can eat while flying.

How Do Bald Eagles Nest?

Photo by Les Zigurski
from les@wildlifeimagesbyles.net
It has been stated for many years that a Bald Eagle pair will mate for life, but if one partner dies, or disappears, the other will if lucky find another mate. A newly bonded pair may work several years on a nest before actually breeding. They may desert one nest site and start again somewhere else, usually within 1/2 mile. A northern bald eagle will begin to nest sometime in February or April. A southern bald eagle will begin to nest in December and January Each nesting pair will spend a great amount of time preparing the nest before any egg is laid. The successful nest is generally located in a large tree, within one mile from water, either a lake or river, where adequate food is available.

Bald eagle nests are generally found from 15 to 36 meters (50 to 120 feet) above the ground, in a tall, sturdy tree. It takes at least two weeks for a pair of eagles to build their nest.

A typical bald eagle nest (eyrie) will range from 1.8 to 3 meters (6-10 feet) in diameter and about 1.8 to 3 meters (6 to 10 feet) high. The nest cavity, where the eggs are laid, will be about 30 to 40 centimeters (12 to 16 inches) in diameter and about 10 centimeters (4 inches) deep.

A pair of eagles, once established, may use the same nest several times over a period of years. Each year more materials are added to the nest, which increases the size of the nest each year that it is used. Nests weighing up to 2 tons have been found.

A Vermillion, Ohio nest measured 2.6 meters across its top and was 3.6 meters high and weighed nearly 1,000 kilograms! Sometimes, eagles will build more than one nest and use them alternately.

An eagle nest is constructed from large sticks, which are laid together to form the outside part of the nest. The center of the nest is filled with dead weeds, stubble and other softer materials, which may be available in the area. The nest cavity where the eggs are laid is lined with grass, dry moss and feathers. Many authorities believe that some bald eagles show such a strong attraction to their nesting site that, if displaced or overly disturbed, a pair may not return to the nest the following year. This fact places great importance on protecting nesting areas from disturbances such as logging operations, land development and recreational activities.

Human activity in the area of a nest during the breeding season must be strictly controlled to avoid disturbance to the nesting bald eagles. The United States Forest Service has developed, and is presently enforcing, human activity controls in bald eagle nesting areas in the National Forests of Minnesota, Michigan, Wisconsin, and Arizona. This may be a great part of the reason the bald eagles population has recovered so well in the past 40 years. The female eagle will normally lay two eggs, and occasionally three, which are about the size of a goose egg (74.4 mm x 57.1 m.) and colored dull white or pale bluish white. Both parents incubate or brood the eggs, which take 34 to 35 days to hatch, and care for the young eaglets. These eaglets remain in the nest for another 12 to 13 weeks before taking their first flight.

After learning to fly and feed themselves, the young immature eagles are allowed to return to the nest for the remainder of the summer. But most young eagles are usually not observed near their parent's nest after the first year.

Where in the United States are Bald Eagles Found?
The search for food forces bald eagles, which nest in the northern United States and Canada, to migrate south in late autumn and early winter, when lakes and rivers in their nesting grounds freeze over. Congregations of these birds may be seen during the winter along lakes and rivers where there is open water, often near dams and power plants.

Primarily fish eating birds, they are found along the coasts of North America and along inland lakes and rivers from the Gulf of Mexico to the Arctic. The birds will winter as far north as ice free water permits. At some time during the year, a bald eagle may be seen in nearly every state in the continental U.S. (there are none in Hawaii).

A majority of Bald Eagles nest in Alaska and remote areas of Canada. A small number nest in the United States in areas where isolation can still be maintained. Major nesting areas are concentrated in: the Far West, (Alaska, the San Juan Islands off the coast of Washington, as well as Washington, Oregon, and northern California); the Upper Midwest (central and northern Minnesota, northern Wisconsin and upper Michigan); and the East Coast (Maine, the Chesapeake Bay area, and Florida).

During winter months, bald eagles are widely scattered throughout much of the continental U.S. Substantial numbers may be found along the Upper Mississippi River and its larger tributaries. Smaller concentrations may be found in other areas, including the deserts of the West and Southwest.

How Many Bald Eagles Are There In North America?
This question is almost impossible to answer. Even if an exact number could be obtained, it would change from one year to the next. Also, because of the migratory habits of bald eagles, estimates of the populations are extremely difficult to make and may be misleading.

Based on several years of surveys in the United States and Canada, the total bald eagle population of North America is estimated to be somewhere between 35,000 and 50,000. That Seems Like Many Bald Eagles!

Why Should We Be So Worried About Their Fate?
There are relatively large eagle populations in Alaska and Canada. Alaska, for example, is thought to have approximately 10,000 nesting pairs, Saskatchewan Province alone is estimated to have between 3500 and 4000 pairs. 0ver 3000 pairs are believed to exist in Canada in addition to Saskatchewan. Prime nesting areas in the United States are unevenly distributed in Florida, Wisconsin, Minnesota, Michigan, Oregon & Washington. There are close to 400 active nests in National Forests alone, and perhaps as many on state and private lands.

Twenty five years ago most states had no nesting bald eagles at all. However, in the last few years many states have had one to thirty pairs of bald eagles successfully raise young. It is this low number of bald eagles in the lower 48 states, where large numbers once existed, which prompts concern for the fate of the species.

Now we are seeing an eight year decline in the percentages of young that are surviving to winter. What the reason is for this decline is unknown. The exact reason for the decline in the 1950s is unknown as well. The Fish & Wildlife Services states that the eagles declined in the 1950s because of DDT. The problem with that statement is the fact that the bald eagle was recovering for many years before the nation banned DDT.

How Close To Extinction Is The Bald Eagle?
The answer could be (and often has been!) debated for hours. Some recent events give encouragement to the belief that the species will never become extinct. Bald eagle eggs from Wisconsin and Minnesota have been transplanted successfully into nests in Maine, where the population suffered a decline in reproductive success because of pesticide contamination.

Young eagles have been successfully transplanted into nests in Maine, New York, Kentucky, Tennessee, Georgia, Indiana and Missouri. Illinois and Iowa now have more bald eagles nesting within their borders than they have had for more than 70 years. So there is hope for the eagles' future.

At the same time, there is a constant struggle to protect essential vital habitat against human disturbance and destruction. The threat of toxic chemicals in their food supply continues.

Wait A Minute!
DDT And Dieldrin Are Banned In The U.S. So They are No Longer A Threat To The Bald Eagle, Right?

Wrong! Although DDT and dieldrin are no longer used in the U.S. without goverment consent, their manufacture continues. United States corporations export large quanities of DDT and other pesticides to foreign countries where their use is legal and widespread. Some U.S. communities are once again trying to get permission to use DDT to kill mosquitoes for fear of West Nile Virus. These chemicals are constantly finding their way back to North America through the food chain. As long as these chemicals, whose residues persist in the environment for many years, are being used in other parts of the world, they continue to pose a global threat to wildlife.

Do Other Chemicals Pose A Threat to Bald Eagles?
During the 1970's, PCB's (polychlorinated biphenyls) received as much attention as DDT received in the 1960's. PCB's are used primarily as an insulating and cooling fluid in electrical transformers. They are known to cause cancer. They are widespread in the environment and persist without breaking down for many years. Like pesticide residues, PCB's accumulate in larger amounts at higher levels in food chains. There is evidence that PCB's interfere with reproduction in wildlife. Heavy metals such as lead and mercury are widespread in the environment. Lead used to be found in a wide variety of products, from gasoline to shotgun shells. Mercury is used in many industrial processes, such as paper and chemical manufacture.

When they enter the bald eagle's food chain, these metals pose a threat. In Minnesota, bald eagles feeding on Canada Geese killed or crippled with lead shot were found to have elevated levels of lead in their blood.

Lead is known to reduce the blood's ability to transport oxygen, which will limit an eagle's ability to fly very far. In Maine, where there are many paper mills, infertile bald eagle eggs have been found to have a higher mercury content than eggs from other areas.

The nation's large chemical companies like Monsanto and Bayer are constantly developing new and stronger chemicals that are used by farmers and homeowners. There is a real threat that one or more of these chemicals are working their way into the food chain like DDT did.

What Are The Penalties For Killing A Bald Eagle?
A federal law protecting both the bald and golden eagle specifies fines of up to $10,000 and/or a maximun of one year in jail, for the intentional killing of one of these magnificent birds. The penalty could be double that for the second killing.

How Much Disturbance Will A Bald Eagle Tolerate?
Bald eagles fear humans at all times, but will tolerate much less disturbance during the nesting season, than at other times of the year. A nesting pair will seek isolation, and any human interference, if prolonged, may drive the birds away from the nest.

During the winter, eagles will roost and feed in groups close to human habitation and activity. However, prolonged and repeated disturbances will send the birds on their way in search of another isolated roost or feeding area. Any disturbance that Disturbances at these sites can lessen the eagles' survival chances as secondary roosts if available, will in all probability not have the vital weather protection that the primary roost provided.

What Kinds Of Land-Use Practices Have Adverse Effects On Bald Eagle Habitat?
Eagles, being large birds, need large strong trees for nesting, roosting, and perching while hunting. Most trees have to be over 200 years old before they can be used as nesting sites for the bald eagle. Logging operations have disturbed or destroyed many nesting territories and potential nest sites, as well as winter roosts. U.S. Forest Service regulations protect nesting territories in the National Forests. But nests and roosts on private land may not be protected, and many times nesting trees used by eagles may be cut down, before their existence is known to the scientific community or general public.

Intensive recreational use of land near nests and roosts disturbs the birds. Increased traffic from snowmobiles, and all terrain vehicles, presents a serious problem, which must be addressed. As the human population expands and moves in greater numbers back into the countryside, the bald eagle is pushed back into smaller and smaller pockets of suitable habitat. Forests are cleared for farming. Vacation homes are built on the shores of lakes where bald eagles nest. In Illinois, the Central Illinois Expressway was constructed right up a valley that eagles used for a winter nighttime roost. In Maine and Washington, supertanker ports and oil refineries have been built near bald eagle roosting and wintering areas. All too often the eagle is forced, by people, to give in and move elsewhere. Most Bald Eagles Nest In The Northern United States And Canada - Where There Is Plenty Of Suitable Habitat,

So Why Is It Necessary To Protect Nesting Sites?
The critical point to remember is that bald eagles are very territorial birds, and most breeding pairs return to the same nest site year after year. They may use the same nest annually for as many as 35 years, or they may build additional nests in their nesting territory, and alternate the use of them from year to year. If their nests are disturbed or destroyed, the pair may never build again. So, although there are large tracts of wild land available to bald eagles, the territorial nature of the birds, their precise nesting requirements, and their past nesting habits, limit the number of suitable nest sites.

Why Are Winter Roosting Sites So Important?
Just as human beings need a warm, sheltered place to go during severe winter weather, so do bald eagles. Winter can be a time of great stress on all wildlife. If that stress can be reduced, there will be a larger and healthier breeding population to migrate North the following spring.

Where Do Bald Eagles Roost In Winter?
Bald eagles generally choose to roost in large trees in protected places within eight miles of their feeding grounds. Along the Mississippi River, for example, they most often roost in heavily wooded, steep-sided valleys, sheltered from northerly winds, or in cottonwoods on islands away from human disturbance.

Bald eagle winter roosting areas have been identified in many parts of the United States - Cobscook and Frenchman Bays in Maine, the Delaware River in southern New York, the Salt Plains National Wildlife refuge in Oklahoma, the San Luis River Valley in southern Colorado, Navajo Lake in northern New Mexico, and the Skagit River Bald Eagle Natural Area in Washington, just to mention a few.

By far the nation's most important bald eagle winter roosting sites are found along the Upper Mississippi River watershed. They include: Ferry Bluff on the Wisconsin River; Eagle Valley, Oak Valley, the Savanna Army Depot, Clarksville and Burlington Islands on the Mississippi River; Rice Lake on the Illinois River, Swan Lake and Squaw Creek on the Missouri River; and Land Between the Lakes in Kentucky, and Reelfoot Lake in Tennessee. We presently know of 59 bald eagle winter roosts that are located on both private and public land along the Mississippi and its major tributaries.

Are All Of These Winter Roosts Protected?
Not by a long shot. Some - Ferry Bluff, Oak Valley, Eagle Valley, Cedar Glenn, the Savanna Army Depot and Plum Island, for example-are protected by conservation organizations or government agencies that manage them. Others are in private hands and are still open to development. Still others are only partially protected and thus threatened by nearby development.

Unlike nesting sites, most of which are in remote areas, many wintering grounds are close to large numbers of people. Human contact with the eagles is inevitable and disturbance of the birds a constant threat. Not to be overlooked is the fact that the use of favored roosting sites varies from year to year, depending on the availability of food. Thus, it is important to preserve as much of the natural ecosystem of these wintering areas as possible. Many are not protected at all.

Why Do Private Organizations Have To Get Involved?
Isn't 0ur Government Supposed To Be Doing This?

Government agencies have a variety of programs which are supposed to help the bald eagle. The U.S. Fish and Wildlife Service is supposed to be keeping a watch on eagle numbers, and maintains laboratories which investigate the causes of death of eagles and other wildlife. The U.S. Forest Service protects and manages bald eagle nesting territories, monitors nesting success and in the past has surveyed bald eagle populations. The Bureau of Land Management and the U.S. Army Corps of Engineers have in the past instituted policies to help protect bald eagles.

However, bald eagles don't nest, roost and hunt just on government land. Also, government policies often force the eagle to take a back seat to other priorities. The Forest Service's policy of multiple use, and the Corps of Engineers' mandate to develop waterways, may conflict with the life requirements of the bald eagle. Thus, private organizations must get involved if the bald eagle is to survive.

What Research Is Being Done To Learn More About The Bald Eagle?
Bald eagles have only recently been the focus of intensive research, and a great deal of useful information is being gathered about their nesting behavior, feeding habits, roosting patterns, and their migrations. Researchers use a variety of techniques to study the birds. Nests are observed with closed circuit TV cameras. Individual birds are outfitted with leg bands as nestlings, so they can be identified later in life. Movements of eagles are tracked using colored markers or radio transmitters on the birds. The results of these research efforts are presented at scientific meetings such as International Bald Eagle Days, sponsored by the Eagle Nature Foundation.