A few years back there was a similar discussion and Bud chimed in. He claimed that the best way to distinguish between them was by the shape of their head as he states here.

We were fortunate to have both a male Coop and a female Sharpie perch on a fence in our yard. We took pictures at the same magnification and were able to manipulate the photos to have the boards the same width. That puts the birds in prospective to the fence to compare size.

Our Audubon western birds states Sharpie size is from 11 to 14 inches. Coop 14 to 21. The size variation is due to the fact that females are normally larger in birds of prey for their safety. Our combined picture shows that a female Sharpie and a male Coop are about the same size as those numbers suggests. The big difference would be in an 11 inch male Sharpie and a 21 inch female Coop. We hope to get them on the fence for that comparison.

We showed this to picture to Bud a while back. He agreed with our identifications and head shapes. The shape of the Coop head in profile is easy to recognize once you know what to look for.

BobnBernie

http://i30.photobucket.com/albums/c301/BobnBernie/CoopersandSharp-shinnedcopy.jpg
----- Original Message -----
From: Bud Anderson
To: tweeters
Sent: Sunday, October 10, 2010 12:56 PM
Subject: [Tweeters] Dan Schurman's Hawk Photos


Hi Dan,

As people have commented already, that is a really nice group of photos.

This bird is definitely an immature male Cooper's Hawk hatched out this summer, perhaps locally.

So you know, I base this opinion on the following five features.

1.) In your first photo, you can clearly see the diagnostic head profile. Cooper's Hawk heads, especially in profile, are totally different than Sharpys. COHAs have a beautiful, smooth sloping profile (similar to a Golden Eagle), uninterrupted by the slight "forehead" above that cere that is so typical of SSHAs.

2.) The eye is much smaller in proportion to the head than a SSHA. In comparative in-hand shots, you will see that both female SSHA and male COHAs have about the same sized eye. This characteristic makes the eye look much smaller on the head of a COHA.

3.) As mentioned by others, the outer tail feathers are much shorter than the central or "deck" feathers, which is one of the classic field marks for COHA but not always so clearly apparent as in your excellent shots. In fact, unlike SSHAs, the outer or "guard" tail feathers are usually about 12mm shorter than the decks in COHAs.

4.) The thickness of the tarsus makes it a male. The thickness of the female COHA tarsus is generally about the same diameter as a pencil. Males approach the matchstick size of the SSHA but in this bird both the thicker tarsus and the thickness of the middle toe eliminate SSHA. In fact, this bird really has a slightly unusually thick toe for a male COHA .

I also find the white throat with a central dark vertical line pretty unique and really, kind of gorgeous.

5.) And BTW, I was just discussing your photos with my friend and local accipiter expert, Jack Bettesworth, and he pointed out another feature to me. This bird has some slight streaking on the crissum or undertail coverts. Jack never sees this in SSHAs.

Hope this is of help....

Bud Anderson
Falcon Research Group
Box 248
Bow, WA 98232
(360) 757-1911
falconresearch at gmail.com



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