Dennis:
>jizz is a great way to recognize
>common species, but it *should not* be used as a primary criterion to
>define or identify rare species.

That's for sure! After all, id by "jizz" requires a lot of experience
with the bird in question, no matter how many books you read! You
don't get that with rare birds - unless you're a vagrant yourself.

Fortunately with raptors we rarely get truly rare species to confuse
us, only common species in rare plumages. So in this case "jizz"
can be very useful for the experienced person to sort out which weird
looking, but common, species is confusing folks.

An example, is broad-winged hawks for us western types. We
generally get a half-dozen or so approaching our trapping stations in
the course of a season (out of a total of perhaps 7,000-8,000 birds
of which we catch and band about 1/2). They invariably get labelled
as Coops when they come straight in, because their wing-beat looks
very much like a Coop and, of course, we are expecting the expected,
not the unexpected.

On the other hand, our most experienced observer, with something like
25 seasons under his belt at eastern and western sites, has probably
seen more broadwings than Cooper's hawks in his life, and can spot
a broad-wing at a country mile, as they say.

To him, they look distinct, no matter what the angle. In several
seasons of working with him off-and-on, I've only beaten him to the
punch on a single broadwing because of my lack of experience
with them - he was looking elsewhere at the time, wanted to throw
himself of the cliff afterwards.

>I've looked at an awful lot of accipiters vis-a-vis the "jizz" thing, and,
>yes, you can often tell Cooper's from Sharp-shinned by relative head size,
>but don't listen to me--instead, look at the photos in the hawk ID books to
>realize that you'd be crazy to rely on this characteristic for a definitive
>ID.

Particularly here in the West, where we have some puny, puny male Coops.
Big mamas are generally very distinct, but little daddies are confusing
even with experience. I've often thought it would be fun to get
Dunne to the Goshutes, all that east-coast whining about how difficult
it is to separate these two species, and their male Coops are nearly the
size of our females! Regular monsters in comparision to our "little
dinkers". I'm convinced this "Coops glide with straight wings, sharpies
with crooked wings" stuff has more to do with wind conditions and
robustness of the bird than any basic physiological difference. I've
seen plenty of male Coops "tuck up" in our often fierce winds at
the Goshutes, when the females remain in a rock-steady, bomber-like
posture. I have no doubt that the larger male Coops on the east
are less buffetted by wind, as well.

- Don Baccus, Portland OR <donb at rational.com>