Thursday, November 20, 2014

Cooper's Hawk vs. Sharp-shinned Hawk + Photo Quiz

    One of the most highlighted bird identification challenges is Cooper's Hawk versus Sharp-shinned Hawk. The two are similar in both shape and plumage, and there's even some size overlap. Separating these accipiters is much easier with birds sitting on a post or in a tree, but it's almost a whole different case with flying birds. I am still not at the point where I can safely ID either species in flight, so this post will cover identifying them when perched. At the end, I have a short Cooper's vs. Sharp-shin photo quiz for those who want to "put to practice" what they have learned.

Perched Adults
    Without a doubt, identifying Cooper's and Sharp-shin is simplest with perched adults. All you truly need is a good view of the bird's head. I always think of adult Cooper's Hawks as having dark contrasting "caps", while adult Sharp-shinned Hawks have a uniform gray "hood." In other words, Cooper's has a dark, slate gray cap, followed by a pale nape and cheek, then the same slate gray coloration on its back and wings. Sharp-shin has gray starting at the head and continuing down the nape, back, and wings. The adults of both species have red eyes.
Above, two spreads from The Crossley ID Guide to Raptors. The first is Cooper's Hawk, the second is Sharp-shinned Hawk. Click each image for a larger photo. 
Perched Juveniles/Immatures
    Separating the immature accipiters is certainly more complicated. Both species have yellow eyes. As stated on page 196 in The Crossley ID Guide to Raptors (which is a book I strongly recommend), co-authored by Richard Crossley, Jerry Liguori, and Brian Sullivan, "Juvenile Sharp-shinned is typically more heavily marked below, with reddish brown, thick streaks, as opposed to the thin, chocolate brown streaks of Cooper's." In addition, Cooper's Hawks appear to have a tawny-colored head. Of course, there are other structural-related clues that aid identification, which you can find in the paragraph below.
Structural ID Marks for All Ages
    Cooper's Hawks have a rather squared head, which is more apparent on adult birds. In comparison, Sharp-shinned Hawks have relatively small, rounded heads; this gives them a big-eyed appearance.
    Tail shape is typically useful, although not 100% reliable. Cooper's has a long tail that is normally rounded with a bold white tip. On the other hand, the tail of Sharp-shin is usually squared with a fainter white tip. Some Sharpies will show a slight notch at the center of the tail tip.
    Finally, the overall shape of a Cooper's Hawk is slim but rangy. Sharp-shinned Hawks appear heavy-chested.
Photo Quiz
     I'll start off by saying that I took these photos a few years ago with a point-and-shoot, so excuse the slightly fuzzy quality. You'll find four photos below, followed by answers and an explanation for each. You can click the images for a larger shot.

1. 1st-year Cooper's Hawk - This bird is obviously not an adult because of its yellow eyes and brown plumage. A closer look reveals a bird with a head, back and wings, and tail that all seem to fit each other proportionally compared to Sharp-shinned Hawk, whose shape gives the impression of a proportionally small head. Note the bolder white tail tip and the tawny, squared head.
2. (2nd-year?) Sharp-shinned Hawk - The small head and big eyes are somewhat apparent despite the angle. The bird's position - seemingly hunched forward - may hint that he/she is rather heavy-chested. Also note the faintly white-tipped, squared tail with the notch just at the center.
3. Adult Cooper's Hawk - The dark "cap" on the squared head is obvious. This bird appears slim compared to adult Sharp-shinned Hawks. Note the bird's eyes, which seem to be small.

4. 1st-year Cooper's Hawk - The same bird as pictured in #1. This photo shows the chocolate streaking and tawny head nicely. The eyes on this bird are relatively small and also yellowish, whereas many Sharp-shins have more orange-colored eyes. The eye coloration is not true for all birds though.