Almost five years ago (1/27/13) I published a post entitled “A Guide To Aging Bald Eagles”. With over 71,000 views to date that post has been my most popular so I decided it was overdue for an update and enhancements. For this version I’ve made the following changes:

• much of the text has been rewritten for purposes of accuracy and clarification
• three images have been added
• a section about distinguishing immature Bald Eagles from Golden Eagles has been included
• formatting has been cleaned up and the title modified

 

As we approach prime eagle watching season here in northern Utah I thought it might be timely to present a guide that would be helpful in aging Bald Eagles as they progress through the 5-6 year plumage stages of becoming those glorious white-headed and white-tailed adults we’re all so familiar with. And since many immature Bald Eagles so strongly resemble Golden Eagles I’ve included information and photos that should be helpful in distinguishing the two.

Raptors, including eagles, that have not reached the adult plumage stage are referred to as immature. Those in their first plumage stage are called juveniles and the term sub-adult is used to refer to any plumage stage between juvenile and adult. Depending on molt sequence, age and timing plumage stages are highly variable so other factors like iris and beak color are also taken into account when estimating age. Eyes gradually change from dark brown to yellow while the beak goes from blackish-gray to yellow as they mature.

 

1/4000, f/8, ISO 500, 500 f/4, not baited, set up or called in

The adult Bald Eagle is unmistakable with its distinctive bright white head and tail contrasting with the dark brown body and wings.

 

 

1/200, f/6.3, ISO 800, 500 f/4, 1.4 tc, not baited, set up or called in

But immature Bald Eagles present very differently than adults, especially in the early stages of development. This juvenile is barely fledged and was still hanging around its nest in southwest Montana. Notice that the plumage is dark brownish-black throughout, though they may have some white or pale mottling at this stage especially on the underparts. Both eye and beak are very dark.

 

 

1/2000, f/6.3, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

This is a first year bird during winter. There’s already some color change in the eye.

 

 

1/800, f/8, ISO 500, 500 f/4, natural light, not baited, set up or called in

A side view of the same bird as in the previous image. The warm, early morning light gives it a bit of a golden glow that wouldn’t normally be seen.  This stage in particular is often confused with the Golden Eagle.

 

 

1/3200, f/8, ISO 500, 500 f/4, not baited, set up or called in

Plumage colors after the first year become increasingly variable. There is more white mottling ventrally and the beak and cere are becoming less dark.

 

 

1/1600, f/6.3, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

The iris is beginning its transformation to yellow and there’s also some yellow at the base of the beak.

 

 

1/1250, f/7.1, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

As plumage stages develop through the second and third sub-adult years the tail becomes whiter with a dark terminal band and more white appears elsewhere. The beak is less dark and as the head becomes lighter it generally leaves a darker “eye stripe”.

 

 

1/1000, f/8, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

The eye is becoming more yellow and the eye-stripe is quite distinctive and often similar to that of an Osprey.

 

 

1/1600, f/8, ISO 500, 500 f/4, not baited, set up or called in

The beak is becoming more yellow (though not as bright as in the adult). Some birds at this stage (like this one) exhibit a few secondary flight feathers that are longer than the rest at the trailing edge of the wing.

 

 

1/640, 7.1, ISO 800, 500 f/4, 1.4 tc, not baited, set up or called in

By the fourth year (though there’s much variation) they’re in transition from immature plumage to full adulthood. The head is mostly white with some dark flecking especially around the eye and forehead near the cere. The tail now lacks the dark terminal band and the beak is nearly completely yellow.

 

 

1/2500, f/8, ISO 500, not baited, set up or called in

A closer look at the same bird allows a better view of the detail of the dark flecking and the beak and eye color at this stage.

 

 

1/1600, f/6.3, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

This bird is very nearly in full adult plumage. The tail is now bright white but there remains a small amount of dark flecking on the head.

 

 

1/1250, f/7.1, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

A fully mature adult. Both head and tail are now completely white with overall dark brown plumage elsewhere. This bird has fish blood on its beak and if you look closely you’ll see that it has a “blown eye” (misshapen pupil, possibly due to injury).

 

 

1/1600, f/8, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

Here we can compare three plumage stages of Bald Eagles in one photo – a sub-adult on the left, a juvenile in the middle and a mature adult on the right.

 

 

1/800, f/11, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

An adult and a first winter juvenile up close.

 

 

1/1000, f/11, ISO 500, 500 f/4, 1.4 tc, not baited, set up or called in

An adult on the right, a juvenile on the left and a sub-adult with some interesting mottling in the middle.

 

 

1/1250, f/7.1, ISO 640, not baited, set up or called in

One of the most common ID errors I see in the field is folks confusing immature Bald Eagles with Golden Eagles (the image above is of a Golden Eagle). Almost invariably novices will call any very large dark raptor a Golden Eagle while in most North American habitats it’s much more likely to be an immature Bald. Here are some guidelines that can be used to distinguish Goldens from immature Balds.

• Golden Eagles have a distinctive golden nape (back of neck) that is usually easily seen in direct light and is completely lacking in Bald Eagles of any age.
• Though it can’t be seen well in this photo the legs of Golden Eagles are feathered all the way down to the toes while the lower legs (tarsi) of Bald Eagles are not feathered.
• Typical of most fishing eagles Bald Eagles have a very large bill, noticeably larger than that of Golden Eagles.

There are other more subtle plumage differences that I’ve chosen not to include here.

 

 

1/1600, f/7.1, ISO 500, not baited, set up or called in

Another helpful tool is behavior and habitat. Golden Eagles very rarely feed on fish and as a result they’re less likely to be found in aquatic habitats so if the eagle you’re attempting to ID is associated with fish, fishing or aquatic habitats it’s very likely to be an immature Bald Eagle. That’s not an absolute guarantee but it’s a helluva clue.

 

For many of us Bald Eagle season is almost upon us so I hope these tips and guidelines will be helpful to my readers. After all, no one wants to misidentify an eagle of either species!

Ron

Notes: 

• For this updated version I’ve used several resources for guidance including “Birds Of North America Online”, my own photos and knowledge and friend and raptor expert Jerry Liguori’s excellent book “Hawks From Every Angle – How To Identify Raptors In Flight”.
• It’s possible that the third and fourth photos from the bottom in this series were baited. I learned after the fact that on some days photographers had been moving some of the carp the eagles were feeding on to more photogenic locations. I don’t believe the birds in these two images were baited, but it is possible.
• I believe all of the images in this post were taken with my Canon EF 500mm f/4L IS USM lens (either version I or version II) though I ran out of time to verify. Most of the photos were taken at Farmington Bay WMA in northern Utah.