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.
  
 

 
   
Solutions
 
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.


5 comments:

  1. Hello Chloe - A birder was searching information on accipiters and came across this post and shared it with me. I love seeing young birders into raptors and the post is great! Keep up the great work and feel free to comment on our HawkWatch International blog. We'll be having raptor calendar giveaways too, so check in, and we will bookmark your blog! Hope you see lots of hawks...

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    1. Thanks, Jerry! I definitely can't wait to see what's happening at HawkWatch International in the next few weeks! ~ Chloe

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  2. I agree with all your id's. In many situations, I'm convinced (after years of birding) that many Cooper's Hawks are misidentified as Sharp-shins. Not sure about middle Tennessee, but in northeast Tennessee I'm think most of the accipiters we see are Cooper's Hawks. A lot of people still rely mostly on that squared-off tail look to distinguish between the two and I agree that it's not a very reliable trait to focus on for id. Nice piece.

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    1. Hi Rick - Cooper's is the dominating accipiter here as well.
      It seems to me that tail shape is based on a person's impression. Looking at photo #1 of the 1st-year Cooper's Hawk, someone might say that its tail looks squared, while I get the impression of it being rounded, especially when you look at the slight curve at the right edge. Then again, there are those truly reversed rounded-tail Sharp-shinned Hawks and squared-tail Cooper's Hawks! Oh well....
      Somewhat surprisingly, tail shape is one of the first things I look at if I think the bird will stick around for a bit. If I see a square-shaped tail with a notch, I'll immediately guess Sharp-shinned and then take a look at other field marks to see if they fit the ID. Same with Cooper's Hawk. So yes, I definitely don't use it or recommend it as a lone field mark but rather a starting point for the official ID. Thanks for the comment!

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  3. Agreed. It's al least a good starting point. I have some photos of some perched Cooper's Hawks that look very square-tailed. I watched and photographed one for almost an hour one time trying to decide between the two. As luck would have it, the bird finally let out a series of cackles which was definitive. Luckily, the voices are very different. However you don't get that kind of cooperation very often. Good birding to you and the family!

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