Juvenile and Immature Bald Eagles
The photos of the juvenile and immature bald eagles below portray the main stages of growth, starting from juvenile eaglets on the nest to the age of sexual maturity at 4.5 to 5.5 years.
The limited number of juvenile and immature bald eagle images here do not cover the wide variety of plumages that young bald eagles go through before acquiring the adult’s snow-white head and tail and a dark brown body.
Juvenile and immature bald eagles are often confused with golden eagles, but the two of America’s largest eagles segregate themselves to mostly different habitat types.
Juvenile bald eagles on the nest flat their wings in-place, performing small jumps as they develop and strengthen their flight muscles.
Muscle exercising begins several weeks before the juvenile eagle fledges. During the later stages of strengthening their flight muscles, the eaglet starts to practice their coordination skills, jumping from branch to branch on large limbs adjacent to the nest.
Technically, a young bald eagle is called juvenile until it replaces the first or natal plumage. The second molt after fledging is initiated in the spring of the second calendar year.
Plumage wise, the bald eagle makes an interesting loop. Their first or juvenile plumage is the darkest. Then they go through a period of lighter plumages that includes extensive white and brown mottling. Finally, they loop back to a dark brown body, this time with a white head and tail.
Immature bald eagles find a mate to establish a breeding territory. Young pair may build one or several practice nests, which are often left unused.
Once they sexually mature at the age of 4.5, the mated pair builds a nest generally reused every year by the same pair. If one of the mated pair dies or disappears, the remaining bird finds another mate and use the existing nest.
After replacing the dark natal plumage of the juvenile, bald eagles enters the age of immature.
Immature birds wear the most diverse and confusing plumages. Though predominantly brown with white mottling, the amount of each tone and pattern varies from individual to individual.
Immature bald eagle plumage at this stage is so unpredictable and diverse that it is of little help to assign an eagle an approximate age.
After leaving the nest, the eaglets depend entirely on their parents for food. Juvenile birds follow the parents anywhere they go, including the feeding grounds.
Young birds wait for the parents to come back with food wherever they are perched. During this period, young eagles begin to take food found by the parents, generally dead fish or carcasses.
It takes a few more weeks for the young eagles to start searching for their food. After they have separated from the parents and become nutritionally independent, young eagles begin to catch dying fish near the surface and waterfowl.
After spending four years wandering, immature birds settle at nesting territory around the age of 4.5 to 5.5 years. Some birds settle closer to the nest they hatched on, while others settle far from it.
Juvenile bald eagles wander over extensive regions during the first few years after they leave their nest. The areas they cover can vary from less than 100 miles to thousands of miles from the nest. The places where they disperse can be a long as the entire length of North America. Some birds that hatched in Florida have been recorded in the northern states of Michigan and Minnesota.
The bald eagle uses its talons to catch dead or dying fish near the water surface. Sometimes the fish they pick is too large to lift, and the eagle gets its wings wet in the attempt to carry the fish and becomes unable to take off from the water and fly. Bald eagles are good swimmers. They release the large fish and paddle with their wings towards the edge, extend their wings to dry them, and fly again.
At the age of 3.5, immature bald eagles begin to acquire a plumage that shows adult birds’ patterns. The head and tail are white with plenty of brown flecking. This transformation takes approximately two years until birds acquire the pure white head and tails.
Immature eagles begin breeding before acquiring the definitive adult plumages. Breeding pairs that included an adult and an immature bird initiated and completed successful breeding attempts.
Bald eagles live long lives. They reach sexual maturity at the age of 4.5 to 5.5 year which is the time they begin to reproduce and acquire the typical white head and tail and dark brown body. Eagles in the wild can live up to 38 years. This number was obtained from a birds that was banded in New York in 2015 and hit by a car in the state of New York. Eagles in the wild are likely to live longer than 38 years.
Bortolotti, G. R. (1984c). Evolution of growth rate and nestling sex ratio in Bald Eagles (Haliaeetus leucocephalus). Ph.D. thesis, Univ. of Toronto, ON.
Bortolotti, G. R. (1986a). Evolution of growth rates in eagles: sibling competition vs. energy considerations. Ecology 67:182-194.
Buehler, D. A. (2020). Bald Eagle (Haliaeetus leucocephalus), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
Fraser, J. D. (1981). Breeding biology and status of Bald Eagles on Chippewa National Forest. Phd Thesis, Univ. of Minnesota, Minneapolis.
Hunt, W. G., R. E. Jackman, J. M. Jenkins, C. G. Thelander and R. N. Lehman. (1992c). Northward post-fledgling migration of California Bald Eagles. Journal of Raptor Research 26:19-23.
McClelland, B. R., P. T. McClelland, R. E. Yates, E. L. Caton and M. E. McFadden. (1996). Fledging and migration of juvenile Bald Eagles from Glacier National Park, Montana. Journal of Raptor Research 30:79-89.
Wood, P. B. (1992d). Habitat use, movements, migration patterns, and survival of subadult Bald Eagles in north Florida. Ph.D. Thesis, Univ. of Florida, Gainesville.
YOU MAY ALSO LIKE