[Mystery bird] Bald Eagle, also known as the White-headed Sea Eagle, Haliaeetus leucocephalus photographed in Lyman County, South Dakota. [I will identify this bird for you in 48 hours]
Image: Terry Sohl, 17 January 2010 [larger view]. You are encouraged to purchase photographs from this photographer. I am happy to email his contact information to you.
Canon 50D, 400 5.6L lens.
Please name at least one field mark that supports your identification.
This is an immature Bald Eagle, as you can see from its plumage, which is brown with variable amounts of white splotching on the underwing coverts, belly, and back. These birds retain their splotchy brown, tan and white juvenile plumage until their fifth (rarely fourth, very rarely third) year, when they reach sexual maturity. Adults can have some black speckles on their white head and tail plumage until at least seven years of age.
Immature Bald Eagles are distinguishable from the Golden Eagle by their more protruding head, larger beak, and stiffer wing beat in flight and straighter-edged wings that are held flat (not slightly raised) when soaring. Golden Eagles have white confined to well-defined patches on the wings and tail -- not scattered about in irregular blotches on the underwings coverts as in immature Bald Eagles. Immature Golden Eagles have yellow ceres while immature Bald Eagles have dark ceres. The legs of immature Bald Eagles are feathered half way down the tarsus, and the feet are yellow. The eyes and beak of immature Bald Eagles are dark brown or black.
The amount and the placement of white on this individual identifies how many years old it is.
My guess is a juvenile bald eagle. The field mark would be the mottled, irregular feather color which is characteristic of juvenile bald eagles in their first and second years. Given this photo looks like it was taken in late fall or very early spring, it might be a yearling, from 9 to 12 months old or a 2 year old. Without any object nearby to get a size estimate, it's hard to get an idea of how big it is. In Maine, 1-2 year old bald eagles get very big, very fast and are quite solid and stocky in build, as this one is. Hawks tend to have a more slender build.
I saw one a lot younger than this on a canoe trip in the MN Boundary Waters Canoe area. It was standing on the same branch of the nest, and Mom (or Dad, I suppose) was on another tree, holding a fish. He was crying away, asking for the fish, and I presume Mom was trying to get him to take his first flight to get the fish.
A week later, at the end of the trip, we paddled through the same lake. It was quite windy, and Mom was soaring well above the trees, enjoying the nice ridge lift off the trees, and there was the fledgling flying back and forth, struggling to find lift in the wrong place and getting tossed around in the rotor. Still crying away, because today's flight lesson on slope lift was not going well.
I agree that it's a juvenile Bald Eagle. An old edition of Peterson's Field Guide says under "Field Marks" for bald eagle: "All field mark". For this one, the overall shape is really what says it for me. The big beak is clearly different than a golden eagle, which is the closest other bird. The white mottling is consistent with juvenile bald eagles I've seen in field guides and in person.