The Bald Eagle is a large, dark brown to blackish-bodied raptor that attains a white head and tail when it is about 4.5 years old. Up until that time, the plumage varies from an all brown juvenile stage through a series of brown bodied plumages that show varying degrees of white on the belly, on the underwings and on the back, with dark or mottled heads and tails. The white patches on the underwings of subadults always occur in the inner linings and "axillars" with some light areas shown in parts of the primaries. By contrast, subadult Golden Eagles always have dark inner wing linings. In flight, they are impressively large with wingspans that range from 6 to 8 feet (1.9 to 2.5 meters) with the smaller birds in the southern populations.
The in-flight profile is of a wide-winged bird whose head extends almost as far ahead of the body as does the tail behind. The wings are held flat when soaring and the wing beat is slow and fluid, rising higher on the upstroke than deeper on the downstroke. Although resident over its entire range (except for the colder parts of the northern interior of the continent), birds are highly mobile as they move from nesting areas to abundant food sources. Migration is well-developed.
SIZE
The Bald Eagle, along with the Golden Eagle, is the larger, regularly-occurring raptors in North America. Its size range is very close to that of the Golden Eagle with the upper extreme measurements of length and wingspan being only slightly longer. Females average slightly larger than males. Length measurements range from 28 to 38 inches (71 to 97 centimeters) and the average is closer to 31 inches (79 centimeters). The wingspan ranges from 66 to 96 inches (168 to 234 centimeters) with an average of about 80 inches (203 centimeters). Weights range from 6.5 to 14 pounds (2.9 to 6.3 kilograms) and average 9.5 pounds (4.3 kilograms). Northern birds are larger than southern birds with the largest breeding in Alaska and the smallest breeding in Florida. The variation in between is apparently gradual.
MORPHS AND MOLT
There are no color morphs of the Bald Eagle, but individuals may be in any one of six stages of molt. The first full plumage is the juvenile, followed by five basic plumages. The definitive or "adult" plumage is attained at the 5th basic stage. The sexes are similar looking and either one plumage per year is acquired or some molting is occurring all year except in winter months in northern birds. Each basic plumage is acquired by molts that begin during the spring and are substantially finished or completed by late fall of the same year. The new plumage is worn throughout the winter until the pre-basic molt begins the next spring.
The juvenile plumage is acquired during the 1st calendar year of life and is retained until the spring of the second calendar year when the first pre-basic molt begins. Thus the birds are about 5.5 years old (6th calendar year) by the time that they acquire the adult plumage. Adult-like plumage may first be observed when birds are 4.5 years old and they are all but indistinguishable from 5.5 year old birds.
Some field guides assign names to the various molt stages as follows:
Age Plumage Field Name
1st year Juvenile immature
2nd year Basic 1 white-belly 1
3rd year Basic 2 white-belly 2
4th year Basic 3 adult transition
5th year Basic 4 adult
6th year Basic 5 adult
Variations in the adult plumage are known and commonly consist of degrees of dark feathering through the eye and crown of the head set against an otherwise white head. Entire dark feathers have been seen in white tails.
SPECIFIC DESCRIPTION
Adult - Perched
Apart from being slightly larger, the female plumage is identical to that of the male.
HEAD
- the entire head, neck and throat are white
- the beak and cere are deep yellow
- the eye is pale to buffy yellow
BODY
- the entire body on the under and upper parts is a dark brown to fuscous black
- the margins of the dark feathers are yellowish brown near the tips giving somewhat of a scalloped look to the body at close range
WINGS
- the wings are dark brown like the body feathering
TAIL
- the entire tail on both surfaces is white
- both the upper and lower tail coverts are also white
- occasionally, small flecks of brown may be seen near the base of a few feathers
LEGS
- the legs and feet are deep yellow
- the talons are black
- the tarsi are feathered with dark brown plumage
Immature (Juvenile - First year) - Perched
HEAD
- all head feathers are a dark, blackish brown
- some birds may have grayish feathering at the base of the beak behind the cere
- the basal portions of the nape feathers may be whitish
- the beak and cere are very dark
- the eye is dark brown
BODY
- the underparts vary from tawny to dark brown with the breast darker brown
- white streaking may be evident where the breast and belly meet or lightly over the entire underside
- the vent area may be whitish in some birds due to fading
- the back and general upperparts are very dark brown to blackish
WINGS
- the coverts are generally dark brown, occasionally with buffy feather margins giving a tawny look that contrasts with the primaries
- the primaries and secondaries are sooty black
TAIL
- the tail is longer than in other plumages
- usually white in the central portion with dark coloration at the base and in a band across the tip
- from beneath, the tail looks whitish near the base with a dark terminal band much as in an immature Golden Eagle
- from above, it can look generally dark with a whitish central band
- some individuals will have a solid dark tail
LEGS
- the legs and feet are yellow
- the talons are black
Subadult (White-belly 1 - Second year) - Perched
HEAD
- the crown is a light buffy brown or tan that contrasts with the cheek and auricular area
- the sides of the face are a darker brown as is the neck
- the throat may show some light feathering and there may be a light area at the base of the beak
- the beak is predominantly blackish gray but some with paler gray cere
- the eye is buffy brown but may lighten to a cream color in some birds
BODY
- the breast is darker than the belly, giving the appearance of a bib even if it is variably streaked with white
- the belly and underparts are very variable and can range from being dark through to nearly white
- the back is generally dark but some white feathering may appear on the upper back to form an inverted triangular patch
WINGS
- the wing coverts are brownish olive and are variably mottled with white
- the primaries are dark brown to black
TAIL
- the tip has a dark band much as in juvenile plumage but overall the tail may appear somewhat lighter
LEGS
- the legs and feet are yellow
- the talons are black
Subadult (White-belly 2 - Third year) - Perched
HEAD
- the crown is palish gray brown
- the throat is largely whitish or buffy white that extends down to the top of the breast
- the cheek is more whitish and the auricular area is very dark giving the birds a look similar to the Osprey
- the beak is blackish gray with an increased amount of yellow mottling at the base that may look like a yellow spot and the tip is buffy-yellow
- the cere is mixed yellow and gray
- the eye is cream colored
BODY
- the breast is darker than the belly, giving the appearance of a bib even if it is variably streaked with white
- the belly and under parts are very variable and can range from being dark through to nearly white
- the back is dark but the upper back will still retain the whitish triangular patch found in White-belly 1 - Second year birds
WINGS
- the upper coverts are all brown but some birds retain white mottling
- basically white all over with brown streaking on the crown and forehead
- a brownish or grayish stripe extends through the eye and back towards the rear of the head
- the beak is yellow with a dark line extending from the nasal area along the crest of the upper mandible
- the cere is essentially yellow or mottled with gray
- the eye is pale yellow
BODY
- most of the body feathers are dark brown but some white flecking may occur on the belly
WINGS
- the coverts are dark brown and may show some white flecking
- the primaries are dark
TAIL
- the tail is mostly white on both surfaces with some dark banding in the terminal portion
LEGS
- the legs and feet are yellow
- the talons are black
Subadult (Adult - Fifth year) - Perched
HEAD
- overall white feathering with usually less brown flecking than in Adult transition - Fourth year birds
- brown streak through the eye is usually less extensive
- the beak is yellow or mostly yellow
- the cere is yellow
- the eye is pale yellow
BODY
- all of the body feathers are dark brown with the margins of the tips a buffy brown color
WINGS
- the coverts are dark brown with buffy edges
- the primaries are dark
TAIL
- the tail and the coverts on both the upper and lower surface are white
- brownish flecking may occur throughout
- there is a dark irregular bandon the tip of the tail
LEGS
- the legs and feet are yellow
- the talons are black
Adult (Adult - Sixth year) - Perched
As described above.
SIMILAR SPECIES
In terms of regularly occurring species within continental North America, no other species resembles the distinctive adults. The White-tailed Eagle has a creamier head, a shorter, wedge-shaped tail and brown undertail coverts. The Steller's Sea-Eagle is larger and has huge white shoulder patches and a longer, more wedge-shaped white tail than the Bald Eagle.
The juvenile Bald Eagle is more likely to be mistaken for a Golden Eagle, but the white wing linings (axillars) and more prominent head in flight distinguish all subadult Bald Eagles from all plumages of the Golden Eagle. The white marks in the underwings of an immature Golden Eagle is in the primaries not the inner wing linings. The immature White-tailed Eagle is similar in all plumages to an immature Bald Eagle but generally appears darker underwing with less white in the axillars and the tips of the tail feathers have white spikes. The long, wedge-shaped white tail of the immature Steller's Sea-Eagle distinguish the various brown plumaged birds from their similarly-aged counterpart Bald Eagle.
OTHER NAMES
The Bald Eagle is also popularly known as the "American Eagle", "Bald-headed Eagle", "White-headed Eagle", "Brown Eagle" (immature), "Fish Eagle", "Old Patriarch", "Common Eagle", "White-headed Sea Eagle", and "Sea Eagle."
ETYMOLOGY
The genus Haliaeetus is Greek for "sea eagle" and is formed from "halos" meaning salt and "aetos" meaning eagle. The reference is clearly about the fondness of this species for ocean edge habitats. The specific name Leucocephalus is Greek for "white-headed" and is formed from "leukos" meaning "white" and "kephale" for "head." Bald is used with its less common definition meaning "marked with white" in obvious reference to the head and tail of the adults and possibly the patchy white markings of the various subadult plumages.
MYTHOLOGY
Eagles have had a long history of symbolic omnipotence and superhuman attributes in many societies. Such characteristics as courage, freedom, independence and truth are common. There are over 300 ways in which various parts of the Bald Eagle's anatomy have been modified in art to impart some meaning, atmosphere or interpretation. The Bald Eagle is an ingrained part of the mythology of many North American Indian peoples and the feathers have been used as part of the head dress for some groups. Carvings and totems are typical amongst coastal communities. As a major recognition of the esteem with which this bird is held, the Bald Eagle was declared the national symbol for the United States of America in 1782, despite the paradoxical opinion that the bird was of questionable moral character, dishonest, cowardly and a feeder upon dead matter and offal.
VOICE
The voice is rather thin and weak for a bird of this size. The female's voice is lower pitched. When disturbed at the nest, the adults utter a kah-kah-kah and if annoyed by the presence of other eagles or large birds they will give a ye-ha-ha-ha or whee-he-he-he repeatedly and with variations. This latter call has been likened to the "neighing" of a horse. Gull-like wails may be mixed with these calls. Similar calls are given by the female when soliciting food or copulating. The wail is also used during pair formation. Adults during display and hungry nestlings will also give a yaap-yaap-yaap call that also has a wailing or gull-like quality. A "chitter" call is given by both sexes when changing over nest duties or during other activities around the nest site.
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