Monday, April 18, 2011
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Solution by Tony Leukering
It was apparent to respondents that this week's quiz bird was a raptor and, if it is still alive, I'd bet that it's still a raptor (just a quick play on verb tense). The relatively wide-and-short wings rule out the pointy-winged kites and the falcons, other than caracaras, of course. Though it's obviously not a really pointy-winged raptor, the fact that it only has four fingers -- something typical of pointy-winged raptors -- and barely that, must mean that it's at least somewhat pointy-winged. The wing length:tail length ratio is off for any accipiter (as are the number of fingers) and the bird's proportions just are not right for a vulture, a harrier, Osprey, an eagle, or Crested Caracara. So, we're going to have to delve into the buteos for this one.
Once among the buteos, we can take the long way 'round, working through relative wing lengths and tail lengths, tail pattern, secondary bulge or no, and various other features. Or we can look for a short cut that might eliminate a lot of the work. Of course, this is one of those things that is usually not encouraged by teachers of bird ID, because short cuts can get one in trouble if one doesn't know how
-- or when -- to use them. However, they are one of the things that make the abilities of highly-skilled and -experienced birders look so magical. That short cut is the number of fingers. Among ABA-area buteos, only Broad-winged and some Swainson's hawks share the trait of only four fingers, and most adult Swainson's usually show a fifth (many/most juvenile Swainson's show only four fingers). These two species also share another trait, the very short outermost primary (p10). On these two species, the distance from the wrist to the tip of p10 is only just over half the distance from the wrist to the tip of the longest primary. Hmm, those two are also the longest-distance migrants of New World buteos. Hmm. Coincidence? I think not, particularly as they share that trait with another long-distance ABA-area raptor migrant: Mississippi Kite.
Once we get to this dichotomy, we have a number of routes that we could take to the correct answer, but the simplest one is tail pattern: Swainson's Hawks never have such obvious and wide white tail bands. I took this picture of an adult light-morph Broad-winged Hawk heading north over Dinosaur Ridge, Jefferson Co., CO, on 22 April 2006.
The leader board is stuffed with perfect scores at this point; "stuffed" meaning that 14 respondents share that 3-of-3 distinction. Finally, some readers of the quiz might be under the mistaken impression that only CO-occurring species are covered here. Long-time quiz readers can certainly tell them otherwise, as such far-flung species as Eurasian Oystercatcher, Pechora Pipit, Gray Bunting, and Yellow-throated Grassquit have been quiz subjects (see the rules).
Incorrect species provided as answers:
Gray Hawk - 1
Sharp-shinned Hawk - 3
Congratulations to the 27 of 36 getting the quiz correct:
Answer: Broad-winged Hawk