John James Audubon, in his monumental art folio of 1827, The Birds of America, included a painting of an eagle he called the Washington Sea Eagle, or Bird of Washington. This majestic bird was much larger than a Bald Eagle and there were marked differences in the coloration and size of the feathered and nonfeathered parts of the bird, leading Audubon to think it was a new species.

Most ornithologists and taxonomists today agree that Audubon’s Washington Sea Eagle was actually a juvenile Bald Eagle, although there is plenty of room for debate. Some experts have made an excellent case for the existence of a separate species that is now extinct, but to my knowledge, no fossil remains of the species have ever been found.

In this discussion I will explore a few of the differences between adult and juvenile bald eagles. This will not only help to explain Audubon’s mistake, if indeed it was a mistake, but it will also help to identify juvenile Bald Eagles in the wild.

The Difference in Size

There is a great deal of size variation in Bald Eagles. So much, in fact, that they have been divided into two species: the Northern Bald Eagle and the Southern Bald Eagle, with the smaller eagles falling into the Southern category and the larger in the Northern category. This categorization reflects where the eagles breed, not where they are found. They travel widely across North America and it’s interesting to note that Audubon made most of his observations along the Ohio River, which is in the center of the size gradient.

A juvenile at the age of a year is skeletally about the same size as its parent but the tail and wing feathers are much longer, giving the appearance of a larger bird. With each summer molt these feathers get shorter until the bird reaches adulthood. The juvenile’s feathers are not only longer, but different in shape, giving the bird distinct aerodynamic properties. This contributed to the fact that Audubon saw distinct differences in flight patterns between his giant eagle and the Bald Eagle.

As with most raptors, females are significantly larger than males. Among the large Alaskan bred Bald Eagles the size difference between a male and female can be as much as 2-5 pounds. Although Audubon knew that males would be smaller, if he were to compare a juvenile female of the Northern species with a mature male of the Southern species it’s easy to see how they could appear to be different species.

The Difference in Color

A Bald Eagle emerges from the nest in shades of medium to dark brown with the exception of the underwing lining which is white. After the first molt the bird takes on a blotchy appearance. Gradually, though a series of summer molts, the coloration becomes similar to that of an adult bird. At the age of 4 to 4-1/2 a young Bald Eagle is almost indistinguishable from adults at a distance, but up close you may see a few brown blotches on the head and tail.

Other color changes include:

• The bill, which is initially dark in color. It gradually changes to a mottled dark and light brown, then to a yellowish brown, and finally to the bright yellow of a mature bird.
• The eye, which is initially sepia in color. It lightens to a pale yellow by the age of 3 to 4.

Our National Emblem

Audubon was disappointed in the selection of the Bald Eagle, which he considered cowardly and unpleasant, as the national emblem. He felt the Washington Sea Eagle would have been a better choice. He compared the Washington Sea Eagle to its namesake, George Washington, in the following passage:

He was brave, so is the Eagle; like it, too, he was the terror of his foes; and his fame, extending from pole to pole, resembles the majestic soaring of the mightiest of the feathered tribe. If America has reason to be proud of her Washington, so has she to be proud of her great Eagle.

This article was written by Jackie Carroll, owner of KGnature.com. Whether you are observing nature around the world or in your own backyard, we have a field guide that is right for you.