The
Bald Eagle:
Haliaeetus Leucocephalus is the largest bird of prey in North America. It is fully
feathered over its entire body, and is referred to as bald only because of the difference in feather colour between the head, and the rest of the body. Whilst reasonably common in Canada, the eagle is endangered in the
USA.
Appearance and Physiology
Bald Eagles are huge. They commonly have a wingspan of 2 yards, and may stand 2 and a half feet tall when perched. Despite this, being birds they are not very dense, and seldom weigh much over 15 pounds.
Both sexes appear very similar, although females tend to be slightly larger than males. The main body is covered in dark brown feathers, and this is contrasted by the bright white plumage of the head. From a distance this could be mistaken for a lack of feathers, thus causing the eagle to be termed "bald". The beaks, talons and lower legs of Bald Eagles are bright yellow.
It is the characteristics of the talons and beak help enable the Bald Eagle to be such an efficient predator. The beak is large, hooked and sharp, and the feet have long talons, controlled by powerful muscles.
These help the eagle to grasp hold of its prey whilst on the wing. The Bald Eagle's hunting ability is further enhanced by its exceptional visual abilities, which enable it to spot prey from a much greater distance than a human could.
Habitat and Range
The Bald Eagle lives only in North America. Most live close to watery areas so that they can find food easily. Bald Eagles tend to migrate during the year, in one of several recognisable patterns. They generally migrate because their feeding waters freeze over during the winter. Canadian eagles mostly travel to the coast of British Columbia, or south to the USA, where almost all birds from that country remain throughout the year.
Behaviour
Except when wintering, or breeding, Bald Eagles tend to be solitary birds. This is because they eat a lot of their, and thus require a large range that is able to sustain a suitable biomass of prey species.
While Bald Eagles are thought of as fish-eaters they are prepared to eat almost anything they can catch. Preferred prey includes fish, water-fowl and rodents. Young eagles in particular are likely to eat carrion, or food stolen from other birds, such as ospreys.
The flying style of the Bald Eagle is a soaring one, in which the wings are not flapped very much. It moves in most respects like other large birds of prey, like the Golden Eagle.
Breeding and Development
Bald Eagles tend to form life partnerships, although when things do not go well, or one partner dies they may repair. Courtship rituals include flying manoevres such as dives, rolls and swoops. The pair will build a very large nest together, in a tree, as close to a food souce as possible.
The eggs, of which there are usually 2 must be incubated for 35 days. The female does most of this, and most of the other tasks involving the young. From the time of hatching, it usually takes the chick around two and a half months to progress to the fledgling stage. Before the flight feathers develop the yound eagle is covered in grey downy feathers. The white head feathers do not develop for several years, typically until the eagle is at breeding age.
Sources
Canadian Wildlife Service
Encyclopaedia Brittanica
"Wildlife Fact Files": 1993
Wildlife on One: BBC Television.