Sharp-shinned or Cooper's Hawk?

I spotted a Bluejay sitting in a tree on King's Highway in Maxville, Wisconsin the other day.  Nothing unusual about that.  What caught my eye was its behavior.

The lone jay was bobbing up and down and squawking.  I could hear the "jay-er, jay-er" alarm call.  But I didn't see what it was that upset the jay.  There were no other birds on the ground or in the trees nearby.

So what's your problem, Mr. Bluejay?

I looked across the street and spotted the problem.  It was in a tree by the shed:  a large Accipiter hawk - probably a Cooper's.  The hawk took off as I opened my car window (to get a photo).  That got me thinking - we've seen shrikes at our feeders, but no Accipiters.  I wondered why. 

Then this morning, I looked out the kitchen window, and there it was:  an Accipiter on the ground below my birdfeeders.

Juvenile Sharp-shinned Hawk plucking a Downy Woodpecker

I grabbed my camera and with great stealth, opened my door.  I snapped two shots before the bird took off with its prey.

Okay... which is it - a Sharp-shinned or a Cooper's Hawk?  I had to pull out the ID books.

Eye color:  Both the Sharp-shinned and Cooper's Hawk juveniles have yellow eyes.  Adults have red eyes.

This one has bright yellow eyes, a juvenile for sure.

So now I go to Wheeler and Clark's Photographic Guide to North American Raptors to look at the differences between the two juveniles.

Belly:  In the Sharp-shinned, streaking of underparts extends into belly.

Back:  The Sharp-shinned has white spots on the back and upper wing coverts.

Eyebrow:  The Sharp-shinned has a pale supercilliary.

My best guess:   it's a Sharp-shinned.  Probably a female (female Accipiters are larger than males).