The bald eagle (Haliaeetus leucocephalus) is a bird of prey that belongs to the Accipitridae family. As an adult, its body plumage is brown, with a white tail and head. On these tones its beak, the edge of the eyes and the legs stand out, which are of an intense yellow tone..
Both the male and the female have the same coloration, however, there is a great difference between them, in relation to size. In this species, the female is approximately 25% larger than the male. Thus, this weighs around 4.1 kilograms, while the female has a body mass of 5.6 kilograms.
The Haliaeetus leucocephalus It is also known as the bald eagle, American eagle or American eagle. It is the national bird of the United States, appearing even on the shield of this nation.
As for the natural area of distribution, it is made up of most of North America, ranging from Mexico to Alaska and Canada. In relation to its habitat, it can live both in the swamps of Louisiana and the deserts of Sonora, as well as in the forests of New England and Quebec.
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The bald eagle has a large head, with a beak of considerable size and hooked in shape. Its body is robust and the limbs are only partially covered with feathers. As for the legs, they lack plumage.
They have short fingers, with large and strong claws. Among these, the rear one stands out, which is highly developed and uses it to pierce the vital regions of the body of its prey.
The plumage weighs around 700 grams. If you lose some of your flight feathers, it may take 2-3 years to replace them..
The bald eagle goes through different stages of development, before reaching adulthood. The newborn baby has dark eyes, pink skin and legs, with flesh-colored claws. After 18 to 22 days, the skin turns bluish and the legs turn yellow.
In the first year, the body, beaks and eyes are dark brown, although they have white axillary coverts. When they are two years old, the eyes are grayish brown and the body is mottled white. At age three, the eyes and beak begin to turn yellow.
In its fourth year, the tail and head are white, while the body is dark. Around the eyes it has beige tones and the tail has several dark spots.
The adult coloration is reached when the Haliaeetus leucocephalus he is five years old. However, it may continue to present some dark spots on the tail and head for several years..
Once sexually mature, it has a bright yellow beak, legs and eye rim. Its head and tail are white, which stand out on a dark brown body.
Both the male and the female have the same coloration in their plumage, but in terms of size, the sexual dimorphism is evident. The female is usually up to 25% larger than the male. This can weigh an average of 5.6 kilograms, while the male weighs around 4.1 kilograms.
As for the length of his body, it is usually between 70 and 102 centimeters. This eagle has a wingspan that ranges between 1.8 and 2.3 meters. In relation to the most distant area of the wing, it measures between 51.5 and 69 centimeters.
The tail is approximately 23 to 37 centimeters long and the tarsus of the leg is 8 to 11 centimeters long. In relation to the beak, the upper jaw or culm, measures between 3 and 7.5 centimeters, depending on the species.
The size varies by region. In this way, the size of the species increases while its habitat is further from the Equator and the tropics..
For example, the South Carolina bald eagle has an average mass of 3.27 kilograms and 1.88 meters wingspan. This represents a much smaller size than those that inhabit the north. Similarly, in Florida there are small species, weighing about 4.13 kilograms..
Juvenile migrant birds found in Montana's Glacier National Park average 4.22 kilograms, while adults weigh an average 4.3 kilograms.
On the other hand, those that are in Arizona during the winter, have an approximate weight of 4.74 kilograms. This notable increase, in relation to the average weight of the species, could be due to the fact that during that time of year the bird spends most of the time feeding.
The largest bald eagles live in Alaska, where females can weigh up to 7.4 kilograms and have a wingspan of 2.44 meters. However, the average for this is 5.35 kilograms and for the male 4.23 kilograms.
Migration is an adaptive behavior that uses the Haliaeetus leucocephalus before the seasonal changes that occur in the region it inhabits. For this reason, birds that live in cold areas are forced to move to temperate zones during the fall..
This is because rivers and lakes freeze, thus reducing the opportunity to access food. This is why a large number of populations that inhabit the south do not migrate, since in these regions the climate does not present drastic variations..
The migratory behavior presents variations in the geographic ranges where it lives. For example, in Yellowstone, this bird migrates locally. It does this solely to increase the chances of finding power sources.
As for the bald eagles that live in Canada, in the winter they generally move towards the United States, in search of a more temperate climate and open water, which offer greater opportunities for hunting fish..
The specialists point out that probably, during the mobilization route, they will use the mountain ranges or the rivers as geographical points of reference. In this sense, the Mississippi River constitutes an important migratory corridor.
The bald eagle selects routes where it can use updrafts, heat sources, and food resources. During migration, the bird could ascend, using a thermal current, to later slide down.
Also, it can rise in updrafts, caused by the action of the wind when hitting a cliff.
Another migratory pattern is the hours in which they fly. They generally start the mobilization in the morning, around 8:00 a.m., when the sun begins to warm the atmosphere. At the end of the afternoon, this bird of prey perches in the trees to rest and sleep.
-Animal Kingdom.
-Subkingdom: Bilateria.
-Phylum: Chordata.
-Subfilum: Vertebrate.
-Superclass: Tetrapoda.
-Class: Birds.
-Order: Accipitriformes.
-Family: Accipitridae.
-Genus: Haliaeetus.
-Species: Haliaeetus leucocephalus.
Subspecies:
-Haliaeetus leucocephalus washingtoniensis.
-Haliaeetus leucocephalus leucocephalus.
The Haliaeetus leucocephalus it is distributed throughout North America. Specifically in the United States, Canada, some regions of Mexico and in several islands, such as Miquelon and San Pedro.
The highest concentration occurs in Alaska, near rivers and lakes in the Midwest, in Florida, and in the northwestern Pacific Ocean. In other regions, there are limited populations. Such is the case of Arizona, Mexico, New Mexico, Vermont and Rhode Island.
Likewise, the bald eagle can become vagrant in Puerto Rico, Bermuda, Belize, and the Virgin Islands. Some of these birds of prey have been sighted in Sweden, Greenland, Siberia and northeast Asia..
The habitat is highly varied, ranging from the swampy areas of Louisiana to desert regions in Sonora and the eastern deciduous forests of New England and Quebec..
In Canada, the bald eagle is found all along the coast of British Columbia, as well as large populations in Alberta, Manitoba, Saskatchewan, and Ontario. Those that inhabit Wyoming are usually found from regions with large stands of Pinus ponderosa, to thin strips of riverside trees, surrounded by grasslands.
When it needs to rest or nest, it does so in mature coniferous stands or hardwood trees. However, for this bird of prey the most important thing is the composition, location and height of the tree. In this way, trees are usually more than 20 meters high, which helps improve their visibility of the space where they live..
Although its habitat may vary according to the range, its selection is associated with several factors. These include the availability of tall trees, the abundance of prey, and the degree of human disturbance..
The Haliaeetus leucocephalus generally prefers areas that are close to large bodies of water, usually within 3 kilometers of it. In this way, it can be found on marine coasts, lakes, rivers, and coastal estuaries..
According to studies, this species shows a preference for those with a circumference greater than 11 kilometers. As for the lakes, they generally have an area greater than 10 km2.
The bald eagle is an animal highly sensitive to human activity. To avoid any contact with man, this bird could move away from important feeding areas.
The place where they live can also vary according to the seasons, thus showing preferences for certain areas.
During the winter, in the months of November to February, between a thousand and two thousand birds are located in British Columbia and Squamish. There, they mainly gather in the Cheakamus and Squamish rivers, attracted by salmon in they are found in that area..
In the northern United States, winter areas are around open lakes, where hunting for fish is made much easier..
The species that live in the south are residents, staying all year round in their territory. On the contrary, those that are distributed to the north migrate annually to the south, in search of a warmer climate.
In the nesting season, the bald eagle does not live in a specific place. Because of this, it can be found in almost any wetland ecosystem, such as rivers, large lakes, shores, or swamps..
In the case that the tree is in stagnant waters, such as in the mangrove swamp, the nest could be located around 6 meters above the ground. On the contrary, if it is on dry land, the height could be between 16 and 38 meters from the ground.
These birds usually nest in the canopy of tall trees, surrounded by smaller ones. In the Chesapeake Bay area of the eastern United States, the Haliaeetus leucocephalus usually perches in oaks (Quercus) and yellow poplars (Liriodendron tulipifera).
The average height of these species is 82 centimeters in diameter and 28 meters high. On the other hand, in Florida, the nesting tree is usually 23 meters high and 23 centimeters in diameter..
In Florida, the bald eagle builds its nest in mangroves, pine forests, river and lake shores, flood plains, and open grasslands. Also, it does so in hardwood swamps and in grasslands with tall, scattered trees..
As for the trees used, there are the cutting pines (Pinus elliottii), long-leaved pines (P. palustris) and cypress trees. However, usually in southern coastal areas, this bird uses mangroves.
In Wyoming, nesting sites are tall pine or mature cottonwood forests, located along streams and rivers. Regarding Southeast Alaska, 78% of the trees used were Sitka spruce (Picea sitchensis).
Throughout history, the various populations of the bald eagle have suffered two major declines. The first occurred in the 19th century and was the product of the mobilization of settlers towards the western regions..
During these migrations, man deforested the land to build settlements and for the establishment of agricultural activities. In addition, there was competition with this bird of prey for fish, an important part of its diet. In addition to all this, the eagle was hunted by the locals.
This situation resulted in the enactment in the United States of the Bald Eagle Law, which established the prohibition of the slaughter of this species in that nation, with the exception of Alaska..
After this, as the populations were just beginning to recover, a new threat emerged, the pesticide DDT. New actions on the control of the use of this chemical compound cause an increase in the communities of the Haliaeetus leucocephalus.
Currently, the bald eagle is considered a species of least concern, according to the IUCN Red List of Threatened Species..
Some of the main threats are:
The felling and deforestation of forests has had dire consequences for this species. By cutting down the vegetation, not only is the environmental balance of the ecosystem being disturbed, but nesting sites are being eliminated. This has a strong impact on the reproductive activity of the animal..
In addition, the construction of urban development carries structures with power lines, against which the bird collides. In this way, he dies from electrocution. Also, the presence of man disturbs this bird, so it is forced to leave its habitat and move to other regions..
The bald eagle is also affected by pollution caused by the oil industry. Such is the case in 1989, where the Exxon Valdez oil spill resulted in the death of approximately 247 birds..
Although recovery was achieved, there is a danger that a similar situation could reoccur, such as pollution from coal-fired power plants and mercury poisoning..
Previously, many bald eagles were killed due to the belief that they could use their powerful claws to capture and prey on lambs. Currently, investigations have indicated that this could occur, but it would be a very sporadic situation.
In addition to direct death, this bird is exposed to lead poisoning or plumbism. Lead can enter the body of the bird when it ingests animals that have died from the use of pellets or when it eats the remains of bullets, used in the case of hunting large animals.
A non-lethal dose of lead severely affects the bird's immune system by reducing the levels of antibodies and the protein lysozyme. This chemical compound participates in the defense against pathogens that could attack the body. In this way, the organism weakens and the animal dies..
Hunting of bison also affects the Haliaeetus leucocephalus, because this animal constitutes an extremely important source in the bird's seasonal diet.
Dichloro diphenyl trichloroethane or DDT is an organochlorine chemical compound, with which some pesticides are made. This is consumed indirectly by the bald eagle, through food and its action in the body affects the absorption of calcium.
Because of this, the shells of the eggs laid by a female that has ingested DDT are thin, causing a high number of eggs to break before the hatchling reaches development. In this way, the population of the bald eagle decreases dramatically..
The use of DDT was prohibited in the entire United States since 1972, while in Canada it occurred in 1989, although its use as a pesticide was already restricted since the late 1970s. These actions caused the bald eagle population out gradually increasing.
The bald eagle is sexually mature between four and five years of age. Their mating system is monogamous, being able to mate for life. When one member of the couple disappears or dies, the other will choose a new partner.
In relation to courtship, it is characterized by spectacular calls and imposing flight displays. These include chases between partners and cartwheels. In that kind of dance, bald eagles link their legs as they fly, spinning in the air. They are then dropped freely and separated moments before hitting the ground..
The vast majority of raptors nest between April and May, but in this species it occurs earlier, in mid-February. As for the nest, it is the largest among North American birds. It can be up to 4 meters deep, 2.5 meters wide and weigh 1 metric ton.
In Florida, a nest was found 6.1 meters deep, 2.9 meters wide and weighing 2.7 metric tons. This is the largest ever recorded for any living animal..
Generally, the nest is used repeatedly, but for a maximum of 5 years. This is because annually, the bird adds new material and becomes very heavy. Therefore, it can break the branch that supports it or be knocked down during a storm..
This species nests on branches, although it can also do so on cliffs, as is currently the case in Arizona and Alaska.
As for the eggs, they measure approximately 73 millimeters in length and a width of 54 millimeters. Weight may vary by geographic area. Thus, in Alaska they average about 130 grams, while in Saskatchewan the weight is 115 grams.
In the incubation of the egg, both parents take turns, but the female does it most of the time. The male who does not participate in this activity is in charge of looking for food or finding material to condition the nest.
The female can lay between 1 and 3 eggs annually. However, rarely do all three young successfully reach the juvenile stage. The one that is born first usually has the advantage of having a larger size and greater vocal strength, which is why it attracts more the attention of parents to this.
Also, occasionally, as occurs in many raptors, the largest of the group can attack and kill their brothers, if their sizes are different..
In the first 2 to 3 weeks of nesting, at least one parent occupies the nest. After 5 to 6 weeks, they tend to distance themselves a bit, often perching on the branches of nearby trees..
As foraging and opportunistic birds, bald eagles have a broad diet, which can include more than 400 different species. However, they prefer fish. Within this group, they usually consume rainbow trout, American eels, white catfish and Pacific cod, among others..
Another important element of their diet are waterfowl, their eggs, and young. Some of these species are common herons, pink and white geese, and tundra swans. They also tend to hunt mammals, such as squirrels, Norwegian rats, and baby sea otters..
In addition, they feed on the carrion of large animals, such as elk, caribou, bison, arctic fox and wolf. These are generally consumed during the winter season, together with other smaller prey..
The flow of the river could affect the success of the hunt, since the Haliaeetus leucocephalus it does not dive into the water to capture its prey. To catch the fish it uses its strong claws, catching those that are on the surface.
This raptor can perch for a long time on a branch, carefully observing the animal it is going to capture. Then it quickly descends and lifts it with its claws. However, to snatch food, they often jump, fly or walk.
In addition to eating carrion, the bald eagle can take prey that other birds have captured, such as ospreys. This method is generally used by older birds, since the young ones prefer to hunt.
The bald eagle often tends to have solitary behaviors, although during the reproductive period it is even. It could also group in the presence of a large carrion, such as the bison.
This species is a powerful flier, being able to flap at speeds of 56 to 70 km / h and 48 km / h, when it is transporting fish. Regarding flight skills, despite the fact that its morphology is not completely adapted for fast flight, it can execute different maneuvers.
Thus, it can reach the geese in flight, and then pounce on them, turning around and digging its claws into its chest.
Contrary to the perception that could be had, considering that it is a bird of great size and strength, its vocalizations are sharp and weak. These can be hissing, chattering, moaning, and ringing, which is a long, high-pitched scream. This is issued when the bird feels threatened. Another way to communicate is through the movements of your head and wings..
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