Closer-Look-Eagles-illustration-by-Kimball-Garrett-450ppi

Illustration by Kimball Garrett

A CLOSER LOOK—Bald Eagle

By Kimball Garrett

Originally published in The Western Tanager, Vol. 46 No. 06 March 1980.

Although now quite rare over much of its range, the Bald Eagle is a familiar symbol to red-blooded Americans and birders alike. The striking white head and tail instantly identify the adult, but there exists a confusing array of sub-adult plumages which will be the focus of this month's [March 1980] article.

Where does one go locally to be treated to this array of plumages? Big Bear and Baldwin Lakes in the San Bernardino Mountains host (between them) some 20-30 eagles in winter, primarily from December through March. Lake Matthews in Riverside Co. also has over a dozen wintering eagles, but these are less accessible to the public. Small numbers may also be found at Lake Cachuma, Tinnemaha Reservoir, the Colorado River, and elsewhere. Historically, the Bald Eagle nested in southern California (particularly on the Channel Islands), but it no longer does so.

Information on plumages comes primarily from field work in the Big Bear area and from unpublished notes by Dave Shea. Remember that it's risky to put an absolute age on an individual: As in humans, there are "late bloomers" and "early bloomers;" protracted molting in the Bald Eagle also confuses the age question. Adult Bald Eagles up to 18 years of age have retained some brown in the tail. Below, then, I have merely presented some guidelines for aging Bald Eagles.

In their first year, Bald Eagles are almost entirely dark brown; there is much white in the wing linings, however, giving them a superficial resemblance to an adult California Condor. This white extends slightly onto the sides, and there may be slight pale mottling in the tail.

In the second year, much of the lower breast and belly is mottled, with white, contrasting with the dark chest. There is also a distinct pale brown to whitish area on the upper back. In this plumage the tail has distinct light and dark zones.

Third year birds resemble those of the second year, but the head has lightened somewhat, leaving an "Osprey-like" dark eye-line.

The body and underwings darken considerably in the fourth year, and the head and tail (although still considerably marked with brown) are contrastingly whitish. Beware, though, as enough dark may be present on the head and tail to give these birds a resemblance to first year birds. Fourth year birds lack the white wing-linings, however, and have a pale bill.

For one or two (occasionally more) years after the fourth year, limited brown smudging may occur on the head and at the tips of the rectrices (often forming a thin terminal band on the tail). A few white feathers often remain on the underparts and wing-linings. In subsequent plumages, birds will appear typically adult.

The beak and eyes lighten gradually. Both are blackish in first year birds. Eyes may be pale yellow (as in the adult) as early as the fourth year, and the beak is usually the yellow hue of the adult by the fifth year.

It is always a thrill to see a Bald Eagle. Perhaps the information above will help add to that experience. 


 

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