Aging Bald Eagles in Flight

Orlando Wetlands Park
Bald Eagle
Adult, Orlando Wetlands Park
There comes a time in the life of every bird photography blogger when it becomes necessary to write on the aging of Bald Eagles.  Yesterday morning I photographed two immature Bald Eagles of different ages, and this morning I added one more.  This made me realize that it's time for this rite of passage. I thought it would be fun to concentrate on aging eagles while they're in flight. On average, Bald Eagles take about five and a half years to reach their definitive plumage--you know, the way they look on U.S. postage stamps (though at least one has taken up to 3 years longer). And this is complicated by the fact that eagles take about six months to complete a molt, meaning that you often see them in the process of molting.  But there are some patterns that allow the observant birder to make educated guesses of a bird's age.

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Bald Eagles
Adult (left) and Juvenile (right), Conowingo Dam
When Bald Eagles fledge and leave the nest, they are in juvenile, or first year, plumage.  When perched, juveniles may look much like Golden Eagles. In flight, however, you should be able to see white "wing pits" and a fair amount of white mottling on the undertail coverts. Their heads may be all brown, though throughout the year the sun may bleach the feathers on the tops of their heads making these feathers appear a bit lighter. The eyes will be dark brown and the bill dark gray with no yellow. The flight feathers of first year birds are longer and more pointed than second generation flight feathers.  This means that the feathers on trailing edge of the wing will be of uniform length and look more pointed than on older birds. All of my photos of juveniles show at least a few signs of second year plumage, but here's some examples.

Central Winds Park
Bald Eagle
Juvenile to Second Year Plumage, Central Winds Park
(This bird has pointed feathers of uniform length on the trailing edge of the wing, dark eye and bill.
This bird has a light cap on the top of its head and some white mottling on the neck,
making me think its moving into second year plumage)
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Bald Eagle
Juvenile to second year, plumage Conowingo Dam
(This bird has pointed feathers of uniform length on the trailing edge of the wing, dark head, eye and bill.
It looks like there may be a couple second generation flight feathers here, and the belly is starting to lighten)
During second year plumage, Bald Eagles will have a mixture of first and generation flight feathers, and since second generation feathers are shorter and flatter, these eagles will tend to have a more ragged look to the trailing edge of their wings. During the second year, the head will lighten, especially on the top of the head, and the eyes will become a lighter brown. You may see some yellow appear at the base of the bill.  From the top, you may also see an inverted white triangle on the upper back of the eagle that does not appear in first year plumage.  The breast will become mottled with white and brown feathers; this is highly variable; some individuals may appear mostly brown, while others may appear nearly all white.

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Bald Eagle
Second Year Plumage, C. S. Lee Park
(This bird has a ragged look on the trailing edge of the wing, and it has extensive white mottling on the breast;
the eye is less dark and the bill is getting some yellow)
Central Winds Park
Bald Eagle
Second Year Plumage, Central Winds Park
(This bird has a ragged look on the trailing edge of the wing, and it has extensive white mottling on the breast)
During third year plumage, Bald Eagles should have a full set of second generation flight feathers (with perhaps a straggling juvenile feather).  This means that the trailing edge of the wing will return to a cleaner look with the feathers of uniform length and flatter tips.  The eyes become lighter and more yellow appears on the bill.  The head and chin will also appear lighter, leaving what may appear to be a dark eye-stripe.  The breast will continue to have white mottling.

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Bald Eagle
Second to Third Year Plumage, Lake Jesup
(This bird has flatter feathers of uniform length on the trailing edge of the wing and white mottling on breast;
the eye is lighter and the bill has more yellow; the chin and neck are still dark like second year plumage birds.)
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Bald Eagle
Third Year Plumage, Conwingo Dam
(This bird still retains a darker eye stripe, has a yellow eye and mostly yellow bill.
There is still white mottling on the neck and wings, and it's losing  its white wing-pit.)
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Bald Eagle
Third Year Plumage, Blackwater NWR
(This bird has mostly dark body and wing feathers, except for a white wing pit.
The head is mostly white, but still retains a dark eye-stripe. The eye is yellow and the bill is becoming mostly yellow.)
Central Winds Park
Bald Eagle
Third to Fourth Year Plumage, Central Winds Park
(This bird has lost most of its dark eye stripe and has a yellow eye and bill.
There is still white mottling on the neck and wings, but it has lost its white wing-pit.)
During fourth year plumage, Bald Eagles begin to look very much like definitive adults.  The head and tail will be mostly white and the wings and body will be mostly brown.  A few white feathers may still appear on the body and wings and the head will have a dingy look especially around the eye and forehead. The tail will be mostly white but may still have dark marks. The eyes and bill will appear yellow, with perhaps some gray remaining on the bill.

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Bald Eagle
Fourth Year Plumage, Conwingo Dam
(This bird looks very much like an adult with the exception of tail, which is still dark near the tip.)
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Bald Eagle
Fourth Year Plumage, Conwingo Dam
(This bird looks very much like an adult with the exception of a smudgy appearance to the head and tail
and a few white feathers on the body. I don't remember for sure, but I think these two images are of the same bird).
In definitive adult plumage, eagles will have brilliant white heads and tails, yellow eyes and bills, and brown bodies and wings. They really are unmistakable

Lake Monroe Marina
Bald Eagle with Rock Dove
Adult, Lake Monroe Marina
In November 2009 I photographed these three Bald Eagles.  The one on the top had caught a fish but was being chased by the other two. In this shot the top eagle dropped the fish to avoid an attack, and the one farthest to the right actually caught the fish mid-air.  Can you age these eagles?

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Three Bald Eagles
Conowingo Dam
Excellent Resources:
Mark A. McCollugh, "Molting Sequence and Aging of Bald Eagles," Wilson Bulletin, 101.l (1989): l-10.
Richard Crossley et. al., The Crossley ID Guide: Raptors (Princeton: Princeton University Press, 2003), 26-29, 34-35.

Comments

  1. Wonderful tutorial, Scott! This is a great time to photograph eagles as we're getting a lot of migrants. I suspect I'll be returning here for a refresher!

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  2. Thanks, Wally! It was a lot of fun putting this together, and Crossley's guide was really helpful.

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  3. A few mistakes in there

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  4. I'd love it if you'd share what they are. I can fix them.

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