I don't often publish stuff in books or magazines that are difficult to see in the field or on birds in flight because minutiae type traits are often not helpful in these situations. But I do like talking about plumage traits and the blog is perfect for it. A friend mentioned something a while back that we had studied years ago, and the subject just came up today so I thought I'd share it. Many juvenile Cooper's Hawks have a pale throat with a stripe down the middle, while many juvenile Sharp-shinneds have a streaked throat. This throat thing is not a 100% diagnostic but is pretty reliable when used with other traits. Its just a secondary trait to take notice of, but nothing to rely on singularly. Anyway, check out the pics below ("click" to enlarge), the first 3 are Sharpies, the second 3 are Cooper's.

Also, it is more Common (especially in the West) for Coops to have streaky throats than for Sharpies to have a single throat line. The last two birds show these types...

 Sharp-shinned Hawk

Sharp-shinned Hawk 

Sharp-shinned Hawk 

 Cooper's Hawk

Cooper's Hawk

Cooper's Hawk

Sharp-shinned Hawk

Cooper's Hawk