On Mon, 29 Sep 1997, Christopher Hill wrote:

[snip..]


As Kenn Kaufman points
> out, the best (subconscious) clue to size we have on most birds is their
> mode of flight, that is, how fast they beat their wings or how "heavily"
> they fly. You don't have that with a sitting bird, so unless you have
> direct comparison with a close bird in the right size range, it's hard to
> get a feel for exactly how big it is.

This is really a good way to do it. If it's at all possible.
find someone who is banding and volunteer to help count raptors
on migration. Chances are there will be at least one person
on site who is skilled and you will boost your own skills
accordingly. The advantage to this is being up on a ridge
where many accipiters are coming through on migration. As you
pick them up in your bins, you can note the frequency of
wing beat..i.e., slower for a a gos, more rapid for Coops
and fastest for Sharpie..at a distance, it's difficult to
get any feel for size, but wing beats will tell you a lot.
I stood next to a guy up on the ridge out of Cle Ellum and
he would ID accipiters with the naked eye while I was fooling
around with my Zeiss...I asked him how he was doing it and
got a valuable lesson. And, the best part was that there was
a constant stream of hawks so you could see them next to
each other and note the difference in wing beat frequency.


Tom