Sharp-shin or Cooper's?

There's been a hawk strafing our feeders this winter. I'd seen enough of it to know it was an adult: gunmetal blue above and rust below, and it was in that gray area of size that makes its species really hard to call. It's the size of a small male Cooper's, or a big female sharp-shin.

That's what makes this ID conundrum (sharp-shinned vs. Cooper's hawk) so devilishly difficult for all but the bird ID oracles. Plumage coloration isn't a whole lot of help, as we'll see below. You've got to go on structure and proportion. On how big the head and bill are relative to the body. And then you have to consider that there's a continuum of sizes that goes from 

small male sharp-shin (barely larger than a mourning dove)

to large female sharp-shin

which is about the size of a small male Cooper's hawk

which is much smaller than a big female Cooper's hawk.

Phew. The overlap zone is tough.

So when I spotted a medium-sized accipiter sitting placidly back in the trumpetvine tangle just off our bird feeding area, I started collecting images of it. At first glance, I thought it might be a Cooper's hawk. When it sleeked down, it seemed to have that hatchet-headed look, and the sooty well-defined cap that often characterizes an adult Cooper's hawk.

And then it raised its crest and I vacillated back to sharp-shinned. 

When its head was puffed up, its bill looked small in proportion to its head. That made me lean toward sharp-shinned, too. As did Corey, who was already calling it a sharp-shinned. :)

I wasn't sure what it was doing there--basking in the sun on this frigid day in the teens? 

until it leant down and picked at something in its talons. Ah! You have prey!

It was so interesting to see the feeder birds going about their business as if there were no hawk there at all. They didn't waste any time. Knew the hawk was at rest and well-fed and thus no danger to them.

As Corey said, "Too bad for Joe, there, but we've got things to do."

 The confounding thing for me was that I couldn't see its legs or feet. And this was a problem because oddly enough, I use those to clinch ID on ambiguous birds on the sharp-shin/Cooper's spectrum.  I decided to settle in with my camera (I'm shooting from inside the studio) and wait until it moved, and I got a glimpse of those legs.

I didn't have to wait long. The bird decided it didn't appreciate being stared at by me, Phoebe and Corey, and it picked up its prey and hopped quickly into deep cover. Oh yes. It was watching us just as closely as we were watching it.

 

I pressed the shutter as fast as I could, hoping I'd get something on both legs and prey.

And this is the shot that clinched the ID for me.  Funny shot, actually, of an awkwardly running, heavily laden hawk. Hard to run on those Dolly Parton claws. 

Those are the spindly legs of an adult female sharp-shinned hawk! Wahoo!

But what did she have in her bill? She'd plucked it practically naked, and eaten more than half of it.

I hoped hard it wasn't my beloved hermit thrush, who spooks around in just that part of the border.

Very impressive black cap for a sharpie. But sharpie she is. See how her legs are pencil-thin when viewed from the front? Those are the sharp, blade-like "shins" of the tarso-metatarsus of a sharp-shin.

The best view. Now her bill looks dainty; her head smallish in relation to her body. It all falls into place as soon as I can see her legs. 

We were itching to know what bird had gone down for her midday meal.

Clearly, it was big enough to give her a Mae West crop!

And it was all but gone, just a few bones left.

I always love to see a hawk get a nice meal. I was hoping hard she'd snagged one of the dozen starlings that have been crapping all over our deck and gobbling down almost every bit of my Zick Dough since the big freeze clamped down. 

We were all heading into town, so we crept out the front door to the garage so as not to frighten her off. She was still eating when we left. We got home around 9 PM and Corey and I went out with his flashlight. She must've plucked it wherever she initially killed it, and brought it to this tangle to eat it in peace. Couldn't find a durn feather, until Corey picked up a couple little bunches of dark greasy green breast feathers, edged in buff. Starling!!

Thank you. Please come back soon and grab as many starlings as you can.  

Here are a couple of my photos of Cooper's hawks, to show their more substantial legs:

A Texas Cooper's, showing sturdy legs, large deep bill, and hatchet-head.

A  juvenile Cooper's from West Virginia. Big ol' feet, strong legs, nicely graduated almost cuckoo-like tail. Head in good proportion to its body. Sharpies often look pin-headed and goggle-eyed to me, especially the little males.

Just for fun, and to illustrate how subtle this stuff can be, I've asked permission to post some of my friend Ellen Pemrick's photos of a bird, almost identical in plumage to ours, in her yard not far from Schenectady, New York. She had decided it was a Cooper's hawk.

 photo by Ellen M. Pemrick

I stared at these photos for a long time, perhaps seduced in part by its similarity to "my" sharpie. I was going back and forth in my mind, but in the end the bill looked too deep and heavy, the head too angular to be a sharp-shin's.

 photo by Ellen M. Pemrick

The Cooper's head has a more angular, hatchet-like quality, and is larger in proportion to its body than a sharpie's. 

When I asked, Ellen provided another shot, that shows a nicely rounded tail, with marked gradation in the lengths of the feathers. Though Corey tells me that this rounded tail can be seen on female sharp-shins, the features I can see on this bird add up to Cooper's, at least for me. Would have loved to see its legs, but we aren't always granted the look we want.

 photo by Ellen M. Pemrick

I hope you've enjoyed this little diversion into accipiter ID, and found it helpful.  Thanks to Ellen Pemrick for loan of her photos!

Disclaimer: By and large, I stay away from thorny ID problems. Although a lot of people send me photos of mystery birds, and I can usually help, I don't consider myself an ID oracle. If bird ID is an Olympic swimming pool, I'll paddle around in the shallow end, thank you. Leave the tough stuff to the big sharks. Who are welcome to cruise in and add to the discussion. I've found it helps a lot to be open to learning from people who know more than I do; to check one's ego at the door in any discourse about bird identification. Tall order for a Leo, but I try.

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