The Bald Eagle (Haliaeetus leucocephalus) is one of the most emblematic and recognizable North American birds.
Most people are familiar with the appearance of an adult bald eagle. Still, few recognize juvenile and immature plumages that precede the impressive white-headed plumage of the adult.
This article describes the age and plumages that juvenile and immature bald eagles go through before attaining the adult plumage.
Familiarizing with these stages will help you identify and age the often confusing juvenile and immature bald eagles.
The highly variable plumage of immature bald eagles
The plumage of juvenile and immature bald eagles shows a good deal of variation. In fact, immature bald eagle plumages are among the most complicated and difficult to classify among North American birds.
Several ornithologists have attempted to describe immature bald eagle plumages. These studies ran into the reality that immature eagles’ plumages varied among birds hatched in the same nest and among birds within and between regions.
The wide variety of plumage patterns among immature bald eagles makes it difficult to link one to a bird’s specific age.
Ornithologist Mark McCollough (1989) studied 135 bald eagles of known age. He proposed broad categories of age and plumage to classify immature bald eagles through continued observation over multiple years.
This article is broadly based on McCollough’s work.
What are juvenile and immature bald eagles?
The terms juvenile and immature are often used interchangeably. However, ornithologists define both terms as follows:
- A Juvenile bald eagle is an individual in its first plumage. The juvenile plumage replaces the coat of down while the eaglet is still in the nest.
- An immature or sub-adult bald eagle is an individual older than one year that has replaced the juvenile plumage for an immature plumage.
Do adult male and female bald eagle have the same plumage?
A question often asked is whether female bald eagles also have white heads.
Yes, both male and female adult bald eagles have white heads and look alike. The only difference between adult birds is the size.
While there is a good deal of variation in size throughout its range, overall, females bald eagles are 25% larger than males.
Telling the sex of an adult bald eagle can be difficult when a bird is alone. When mated pairs perch side by side, the size difference between sexes is noticeable.
Male and female measurements
Weight: 6.6 – 14 lbs
Length: 31 inches (head to the tip of the tail)
Wingspan: 5.9 – 7.5 ft. (Adult)
Lifespan: 20 years (In the wild)
Speed: 75 – 99 mph (Diving)
Male and female birds look alike, but the females can be up to 25% larger.
How about immature eagles?
There appear not to be any difference in plumage among immature birds. All immature bald eagles appear to follow similar changes in plumage with age and, whether male or female, acquire the definite plumage at about the same time.
Classification of immature bald eagles by age and plumage
Juvenile to 1 1/2 Year
Juvenile bald eagles leave the nest with a dark brown plumage. This plumage is the darkest and least variable of all the subsequent young bald eagle plumages.
Fledging juveniles keep this plumage for about 6 months before beginning to molt into another plumage. The coloration of bare parts (beak, face, legs, and feet) also begins to change after the first 6 months after leaving the nest.
A first year eaglet is entirely dark brown with white flecking on the wing’s underside, axillaries, and on the belly.
This is the plumage an eaglet leaves the nest in.
The juvenile bald eagle’s plumage is the least variable among al immature plumages.
Fledgling birds shows a blackish-brown breast that may contrast with the lighter colored belly.
After six months, the immature eagle begins to turn lighter brown.
More white flecking begin to appear on the breast and the underwing.
The beak and cere are blackish gray.
By the end of the first 1 1/2 year, the beak begins to turn colors, but this is variable with some birds keeping their dark beaks well into the second year.
In flight, a 1 1/2 year-old eagle may show an increasing but variable amount of white flecking.
The wings of a first-year bird are wider and have a more “rounded” trailing edge.
2 1/2 Years
The 2 1/2 year of age includes some of the most variable plumage stages of immature bald eagles. Some birds can remain relatively dark with white flecking, while others can have a mostly white belly with brown flecking.
The plumage pattern combinations in between can be confusing and useless to age an immature bald eagle other than saying that the bird is about 2 1/2 years of age.
A relatively common field mark during this age period is a dark breast that contrasts with a paler throat and belly.
The legs also become more yellow.
Another field mark is a whitish inverted triangular patch on the mantle.
The eyes (iris) continue turning lighter brown.
The bill begins to turn yellow-brown.
During the immature stage, the pattern and amount of white flecking and mottling is rather variable making difficult to tell the age of the immature bald eagle.
Some birds show a whitish tail with what appears to be a brown terminal tail band.
In flight, a 2 1/2 year-old bird shows a heavy white flecking and mottling on the underwings, the back, and belly. Some birds show a dingy white belly.
Some birds show a jagged trailing edge resulting from old and new shorter wing feathers.
3 1/2 Years
The year 3 1/2 marks the transition to the typical adult plumage. The white mottling of the underwing coverts and belly begin to darken while the head and tail begin to turn white with much brown flecking.
Some ornithologists 3 1/2 year-old bird sub-adults.
At 3 1/2 years-old, the head and tail begin to turn white brown flecking.
An important field mark of Sub-adult bald eagles is a conspicuous dark band or patch through and behind the eye.
The bill is mostly yellow. Some individuals show brown streaks or lines on the culmen or top of the beak.
The eyes (iris) are light brown but not nearly as pale as in an adult bird.
In flight, a 3 1/1 year-old bird resembles an adult with a dingy white head and tail.
The contour or body plumage turn increasing homogenously dark brown.
4 1/2 to 5 1/2 or Definitive
During the 4 1/2 to definitive plumage period, bald eagles acquire the adult plumage. The head, neck, and tail, and upper and undertail coverts turn white, and the body turns dark brown.
A 4 1/2-year-old bird may still show a few brown flacking on the tail and head, which are progressively lost.
Only approximately 25% of the birds acquire the adult plumage at the age of 4 1/2 years, but all or 100% of bald eagles acquire the pure white head and tail adult plumage at the age of 5 1/2 years.
Once a bald eagle acquires the adult plumage this is kept throughout the life of the bird.
The head acquires the pure white, but may show some brown flacking. Some birds take up 8 years to acquire a pure white head and neck, but most do it in 5 1/2 years.
The bill is now bright yellow.
The eyes (iris) is yellowish-white. The legs become bright yellow.
The tail turns overall white but still may show some brown flecking, in some individuals.
Some birds take a few more years to acquire a pure white tail and tail coverts.
In flight, a 5 1/2 year-old bird shows the adult bald eagle plumage.
While the head, neck and tail may still show some brown streaks, these are only noticeable at close range.
Do juvenile and immature bald eagles migrate?
Juvenile and immature bald eagles disperse from their natal territories in a somewhat complex manner; without a predictable direction or distance from the nest. They are also largely nomadic
Bald eagle biologists indicate that juvenile and immature bald eagles are largely nomadic because they do not hold breeding territories and are not tied to a particular area.
The availability of food affects bald eagles of all ages and is often linked to weather conditions. In cold winters, bald eagles generally move south in search of better foraging opportunities. Some birds return to their territories when weather conditions improve, and others return only to breed.
Most adults bald eagle, generally, do not migrate. However, they will perform local and regional movements in response to the availability of food.
Migrating Patterns of immature bald eagles
Bald eagles in Alaska and the Pacific Northwest follow the salmon migration moving in the salmon’s direction where dead fish is readily available.
Eagles breeding in Canada and the Northeastern U.S. migrate along with feeding areas on the Atlantic coast. However, many birds stay in their territories as long as lakes, rivers, and other water bodies are still available.
Juvenile and immature birds from Florida move north along the Atlantic coast, while others migrate onto the Great Lakes region.
Habitat used by juvenile an immature bald eagles
Juvenile bald eagles remain associated with their parents for 4-10 weeks after fledging. Some immature eagles depend entirely on their parents for food during the first 4 weeks after leaving the nest.
Once the young bald eagles become independent, they feed on dead fish or carcasses. They are unable to catch live prey for about the first 6 weeks after they leave the nest. Juvenile bald eagles are opportunistic, eating mostly dead fish.
Overtime, juvenile birds, begin learning to catch live prey, which expands the habitat types they can use.
Three-year-old immature bald eagles begin frequenting areas with concentrations of waterfowl where they use and refine their hunting skills alongside experienced adults.
Overall, adults and young bald eagles use largely the same habitat, particularly when food is abundant. Conversely, when food is scarce, adult birds use prime areas, relegating younger birds to marginal foraging areas.
Juvenile and immature birds are noted for staying longer around carcasses or accumulations of dead fish.
Juvenile and immature bald eagle crisis
During the early 1970s, the bald eagle population experienced a steep decline due to DDT’s widespread use.
Seeing juvenile and immature eagles during the 1970s was a rare event. This was because the components of DDT interfered with female bald eagles’ ability to produce eggs with thick-enough shells.
Most nests failed because the eggs would easily break with just the gentle weight of an incubating adult. Very few juveniles were produced every year.
On what is now a successful conservation story, the Bald Eagle has regained numbers and continues to recover to the point that it is now fairly common in certain areas.
Bald eagles are now seen near bodies of water and sitting on utility posts and other places.
I hope this article helps you tell the approximate age of the next juvenile or immature eagle you see. Knowing the approximate age of a bald eagle will help you take accurate notes.
If you can recognize individual birds in your area and see them over the years, you can document the plumage changes as they become adults.
- Buehler, D. A. (2000). Bald Eagle (Haliaeetus leucocephalus), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
- McCollough, M. A. (1989). Molting sequence and aging of Bald Eagles. Wilson Bulletin 101:1-10.
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