Eric,

Your description of the Bald Eagle at Vashon sounds like a bird in Basic III
(or thereabouts) plumage. Regularly referred to as the "Osprey-stripe
stage."

Aging Bald Eagles by their plumage can be tricky due to the incredible
individual variation displayed, but in a nutshell they change from the
totally dark brown, with whitish markings on the underside of the wings,
with a mostly black bill (at fledging = juvenile) to the white head and
tail, with yellow bill at sexual maturity (at approximately five years of
age). The Osprey-stripe stage or Basic III is the plumage of the bird's
fourth year.

For a good description, with excellent photographs, check out (or buy) a
copy of Wheeler and Clark's A Photographic Guide to North American Raptors
(Academic Press, 1995 - about $ 30). The text goes into the details and the
photographs are superb. Bald Eagle plumages are illustrated with 19 photos.
Red-tailed Hawks with 48 photographs of various plumages and morphs. It is a
guide well worth the money.

Hope this helps,

Martin Muller, Seattle
MartinMuller at email.msn.com