Monday, March 06, 2006

February 6 notes: a visitor!

An immature bald eagle landed in the nest today (see archived images). Often called "juveniles" (a term better used for first-year birds) or "young" eagles, immatures are brown-feathered over the entire body with variable white mottling patterns. They do not have the white head and white tail of an adult bald eagle: the highly distinctive plumage that signifies sexual maturity. The buffy highlights in this visitor's head plumage, light feathering of the throat area, dark beak, and brown eye color suggest that it is a second-year bird. It's possible to age immature bald eagles by focusing on these features since head plumage, beak color, and iris color all change in predictable patterns through the first 4 years. Patterns of white on body feathers can be quite varied. Immature eagles are not smaller bodied than their adult counterparts.

This bird could be a visitor to Maine or a native. We have identified eagles from as far away as Florida, Michigan, and Saskatchewan spending time in Maine! Nest intruders may be briefly tolerated at this time of year. Territorial adults usually rudely escort them away during the nesting season, even if is an offspring from previous years attempting to visit home. Only once in more than 50,000 observations of nests here in Maine have I witnessed breeding adults allowing a visiting immature eagle to land on an active nest.

Management comments: Non-breeding eagles (especially immatures) often have a nomadic lifestyle for the first few years but tend to return to their natal area as they approach adulthood at 4 - 5 years of age. Immature eagles from Maine have been seen along the Atlantic seaboard from Nova Scotia to South Carolina. Death rates of eagles are higher in their early years due to inexperience and wide-ranging habits. -- Charlie Todd, Maine Dept. of Inland Fisheries and Wildlife


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