How To Tell The Age of a Bald Eagle

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>[!WARNING] Please Note! >I'm still trying to find and photograph an eagle which is in it's first year. I think I've photographed one or two but not in the same format as the rest to make it a nice comparison. I'll update when I manage to photograph one.

Ever wondered how to tell the age of a bald eagle? I have, so I set some time aside to do some research and then put it into practice by observing birds in the wild. Bald Eagle plumage varies by age for the first five or so years of their life. When birds exhibit this kind of plumage change they are said to have delayed plumage maturation. This can be useful as it makes it easier to derive the age of a bird from observation.

Below I'll share images of birds in yearly stages from juvenile to full adult, starting at half a year when young birds develop their first full plumage.

The main indicators of age are:

The head and tail feathers.
The eyes.
The bill and cere.

A birds cere is the area where the nostrils are found.

First Year

In the first year, eaglets will moult from downy feathers to full feathers before they fledge. The are mostly brown with patches of white. The bill and cere are dark brown/black and the eyes are deep brown. These birds can be mistaken for golden eagles if you don't know what to look for.

--No Photo Yet--

Imagine the photo below but with a darker bill and cere, and almost no white on the head.

Second Year

White feathers are starting to show up on the head, and the bill and cere are starting to lighten with a yellow tinge. The eyes are still very much brown.

*Second year birds are mostly brown with some white feathers throughout. The head is mostly brown with some white starting to show and the tail is all brown.

In the second year eagle, the bill is a dark brown/black with only a small amount of yellowing. The cere is mostly black with some yellow starting to show. The eyes are deep brown.

Third Year

Lots of white feathers on the head and the bill and cere are almost fully yellow, albeit dull. The eyes are starting to lighten too.

Third year birds are motled throughout but start to show the dominant white on the head.

Notice the yellowing bill with subtle dark areas and a 50/50 white and brown head. The body feathers are also light brown with patches of white. This indicates a young eagle in its third winter.

Fourth Year - Sub-Adult

Full head of white feathers with only a few brown feathers showing. All body feathers are brown. Bill is fully yellow with a light tinge. Eyes are light yellow. A dark terminal band is visible on the tail feathers.

A fourth year bird showing an almost complete adult plumage.

Notice the yellow bill and cere, yellow eye, but patches of brown feathers on the head. This indicates the bird is nearing it's full adult plumage but still has a season to go.

Here you can see the black patches at the end of the tail feathers which make up the terminal band. This indicates the bird has not reached full maturity.

Full Adult

Mature adult has a pure white head, fully brown body, rich yellow bill and cere, and eyes deep yellow. Terminal band completely gone, pure white tail much like the head. This eagle is in its 'definitive plumage', the final version of it's plumage.

An adult eagle showing definitive plumage.

In full adult plumage the head is fully white with no brown feathers. The bill, cere, and eyes are all deep yellow.

There is no terminal banding on the tail feathers.

Comparison Figures

These comparisons should make it clear to see the differences as an eagle ages.

Full Body Comparison

Head Comparison

Summary

I wanted to wrap this up by just covering a bit about the differences between male and female bald eagles. I'm yet to photograph two together but when I do I'll update this section. There are a few way to try tell the two sexes apart, but there isn't really a fool proof method.

Females are around 30% larger than males. This is obvious when two are perched side by side but not much use when they're on their own.
Females typically have a deeper bill depth but again, hard to tell in the field.
Females have a longer hallux talons (rear facing talons) which can be twice as long.
Finally, males are generally more slender and less stocky owing to their role as chief hunters during breeding.

Thanks for reading, I hope you found this useful. If there is anything you think I shoudl add, or if you noticed any errors please do let me know. I'm learning as I go here!

Created by Niall Bell (niall@niallbell.com)