In response to Loughman’s request for identification assistance, she received this message from Jill Harley at the Golden Gate Raptor Observatory:
What a funny posture you caught this bird in! This is an adult Cooper’s Hawk – as you guys noted it has it’s hackles raised so the head looks flat, which Sharpies rarely do. Also, that darker cap on the top of the head, with the distinct line at about eye-level above which it’s darker is typical of Coops – Sharpie’s caps will appear to be all one color.
I agree that the darkness under the chin appears odd, but I think most of that is just because we are looking at stills where the bird’s head is turned, so that the gray on the side of the face appears to stretch down to the chin. There’s a few seconds in that top movie, right when the bird turns to face forward and looks up, and you can see that there is streaking under the chin, that it’s not all gray. And in that second photo down, the head is not quite as turned, and when you look closely you can see streaking under the chin. Though I agree there is usually a more distinct line between gray cheek and streaked upper breast! It is probably a combination of the bird being heavily streaked all the way up to the chin, along with the weird posture and resolution of the photo.
Accipiters can be very difficult to tell apart! And there is individual variation in the amount of barring and streaking they can have. I get a lot of emails asking for ID help, I’m going to paste in below some of the most reliable field marks I tell people to look for. But working with pictures is often difficult – in this case the head is giving the only clues. Ideally you will be able to use a combination of field marks instead of relying on one or two.
Overall, Sharpies are smaller, but since female hawks are larger than males, the male Cooper’s Hawks just barely overlap in size with the female Sharp-shins. There are a few good ways to tell them apart, especially if you have a picture – Cooper’s Hawks tend to have a fiercer-looking face – their eyes are set farther forward, and they often raise their hackles (feathers at the back of their neck), giving them a more square-headed appearance. Sharpies have a smaller, rounder head with the eye more in the middle of the head, giving them a wide-eyed, surprised look.
Of course, normally you would not be able to see that in flight very well. Cooper’s hawks tend to have more stable flight with a straight front edge to their wing (in a soar) and a larger head. Sharp-shinned Hawks tend to flap a bit more, and be a bit more unsteady (especially fighting the wind), and often soar with their wings hunched forward a bit, which makes it difficult to see their smaller head. The tail can be a good clue as well – Sharpie tail feathers are all about the same length, so their tails look square, where the outer tail feathers on a Cooper’s Hawk are shorter than the inner ones, make their tail look rounded at the end (this can be hard to judge depending on how they are holding their tail…).
The juveniles have the brown upperparts and streaks on the underparts. Adults of both species have gray upperparts (can appear fairly brown in some lighting though) and have orange barring on the underparts All have the bands on the tail – Coopers tend to have more white at the tip of their tail than Sharpies but again that is variable…
Thanks for the email Kay! Good luck with the webcam. We are working on updating our website (long overdue!) so be sure to check back, we’ll have much more useful ID help on there soon.
You may also want to post these links to ID tips for Accipiters – the top two are white papers by Rich Stallcup, a naturalist and research associate with the Point Reyes Bird Observatory. The other two are ID tips from the USGS Patuxent Bird Identification InfoCenter for Sharpies and Coops.
http://www.prbo.org/cms/docs/observer/focus96accipiters.pdf
http://www.prbo.org/cms/docs/observer/focus82accipiters.pdf
http://www.mbr-pwrc.usgs.gov/Infocenter/i3320id.html
http://www.mbr-pwrc.usgs.gov/Infocenter/i3330id.html
Take care,
Jill
Jill Harley
Research Assistant/Office Manager
Golden Gate Raptor Observatory
www.ggro.org