Janet,

About your request on how to identify individual adult Bald Eagles (Wed, 27
Nov ).

The simple answer is: with a very good look at the birds and a bit of luck.
The first part requires a scope or birds perched close enough that you can
scrutinize it with binoculars. The second part consists of imperfections in
their plumage. For instance, the pair nesting at the south end of Mercer
Island (Seattle) these past two years, are fairly easy to distinguish. The
male has circles of smudged/dark feathers around his eyes (like he never gets
enough sleep) and a brown feather above his left eyebrow. He replaced those
features during molt or a male with the exact same markings replaced him. I
vote for the same male in consecutive years. His partner has an extremely flat
crown and one brown feather on the center of her crown. That's how I tell
these two from other eagles in the area.

But as you can see, good detailed looks and a bit of luck is needed. Other
features to look for are gaps in flight feathers. This won't help during molt,
but occasionally a bird will damage and loose a feather and have a telltale
gap for some time. This time of year that should help.

To illustrate the usefulness and shortcomings of this method:
In December 1992 I thought I was seeing a lot of Bald Eagles in the Green Lake
(Seattle) area. I visited the lake frequently, but not all the time. Yet
between January first 1993 and March first 1993, I had 78 eagle sightings on
the lake alone. I took photographs of as many birds as I could, adults and
sub-adults, even when I was convinced I was watching the same bird on
consecutive days.
By comparing the slides and notes on plumage while studying perched birds with
my scope, I concluded there were a minimum of 19 individuals involved in the
78 sightings. I say a minimum, because several adults had no distinguishing
markings I could discern (the shortcoming in this procedure). Two sub-adults
on consecutive days looked identical to me, but when I compared the pattern of
light and dark feathers of the underwing (as they soared above the lake) in
the slides, they turned out to be two different birds (the usefulness of this
procedure).

Hope this helps, good luck!

Martin Muller, Seattle WA
martinmuller at msn.com