Only fifty percent of Bald Eagle fledglings will survive their first year. Only two species of eagle are known to breed on the North American continent. One, of course, is the bald eagle. Immature bald eagles are often mistaken for the other North American native, the golden eagle. The golden eagle has a distinctive crown of feathers on the head and neck from which it derives its descriptive name. The golden eagle also has feathers all the way to its toes, unlike the bald eagle, which has featherless feet. Golden eagles also prefer rugged uplands to the watery habitat of the bald eagle.
The bald eagle, scientifically known as Haliaeetus leucocephalus, meaning white-headed sea eagle, is not true to its name it our modem language. A bald eagle is, of course, not bald. This eagle was named at a time when "bald" was a common description of white markings on the face or head of an animal.
The eagle belongs to the order Falconiformes,
a
grouping of birds that includes about 275 species worldwide. This order
includes those birds considered carnivores by virtue of their unique design,
which enables them to hunt and eat meat. The eagles' razor-sharp talons,
hooked beak, and keen eyesight all aid these remarkable birds in the hunt.
| No North
American bird grows faster than an eagle chick. At 6 weeks old, a healthy
chick should weigh between 8 and 9 pounds.
One to three eggs are laid in early spring. Eagle eggs are plain white and close in size to a goose egg. The female incubates the eggs for approximately 35 days. The male shares in incubating the eggs or brings food to his mate. There is almost always at least one adult on the nest for the first two weeks. Eaglets are never left unattended for long. Though they may not be on the nest proper, the adults are never far away. |
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Eagles tend to use the same nests year after year. Each spring, they repair and refurbish the nest until it meets their approval. These continual additions to the nest enlarge it to enormous proportions. One observed nest measured eight feet in diameter and probably weighed over two tons. If an eagle's nest is destroyed for any reason, they are known to build another very close by. Once the nest has been made egg-worthy the female lays one to three eggs, each a day apart. Incubation begins immediately with the female shouldering most of the nest-sitting duties. Her mate takes on the responsibility of hunting for both of them while they wait for the first egg to hatch, approximately five to six weeks after it was laid. Once the chicks hatch, they require near-constant attention and protection from the elements, with both parents now sharing the responsibilities.
Perhaps the greatest survival challenge for eaglets in the nest comes from each other. Since the eggs are laid a day or two apart, the first-hatching chick will have a head start on second or third chicks. The larger chick will peck at and attack the smaller chick(s), gobbling up the lion's share of the food that the adults bring to the nest. Many second- and third-hatching eaglets fail to live beyond the first two weeks. Strangely enough, adults do not try to protect the eaglets from each other.
Even if the fledgling eagle survives life in the nest, the battle is not yet won. Young eagles take time to achieve the grace and know-how of an adult. This can be particularly disadvantageous with the coming of winter or in times of food shortage; only about fifty percent of bald eagle chicks will survive their first year. Despite this grim statistic, under normal conditions the number of young eagles that do make it is more than enough to sustain the current population.
Bald eagle migration can take many forms. Some eagles stay in their nesting and breeding grounds year round if food is ample and waterways remain open for fishing. Others travel a considerable distance to find a suitable place to spend the frigid months ahead. Some will even travel as far south as Texas from Canada and Alaska to spend the cold winter months.
Eagles are leisurely migrators. They ride obliging wind currents, traveling 100-125 miles per day, typically hunting in the morning and migrating in the afternoon when flight-enhancing thermals are more likely to occur. Once the eagle arrives at its destination it settles in for a relatively relaxing winter spent roosting and waiting for its life cycle to begin anew with the warm winds of spring.
Despite its status as our national symbol, the bald eagle has not always enjoyed widespread popularity and acceptance. Once thought to be an insatiable predator with a taste for the kill, thousands of blameless birds were shot on sight by ranchers and sportsmen intent on protecting livestock and wild game. In truth, most of the "kills" attributed to eagles were actually the victims of other predators or natural phenomena.
Eagles have faced serious survival challenges from other sources including DDT poisoning, accidental trapping and electrocution on power lines. The conservation movements of the 1970's, however, made great strides in the understanding and preservation of the eagle. Today the survival of this most magnificent bird is a certainty - its legacy will endure.