Monday, June 13, 2011

Quiz #403 (2011-2-11) Solution

Click on picture(s) for a larger view.

Solution by Peter Wilkinson and Tony Leukering

As Peter Wilkinson wrote: "Ah, a small buteo (that is, smaller than Swainson's)." Though raptors, in general, provide lots of angst for birders, perhaps none but the accipiters provide more than the small buteos. This week's selection of responses proved the case, as only 50% of respondents got the correct answer. As Peter Wilkinson provided a fairly thorough answer, we'll start with his words. Remember, he's a Brit and does not get a lot of practical experience with ABA-area small buteos.

"The larger buteos are ruled out by wing/tail ratio and Swainson's itself is ruled out by the wings not being pointed enough. That leaves Gray, Red-shouldered, Broad-winged, and Short-tailed. Gray can be ruled out by the lack of barring on the thighs and Short-tailed has a completely different underwing pattern, leaving us Red-shouldered and Broad-winged. Juveniles of these species can look rather similar. The classic translucent panel on the primaries of Red-shouldered (which this bird appears to show) can be mimicked by the effects of the moult of second-calendar-year Broad-wingeds, and this bird hass clearly started its primary moult. Fortunately, they can be separated by the tail-barring (more in Red-shouldered, less in Broad-winged) and the number of fingers (5 in Red-shouldered, 4 in Broad-winged)."

Thanks, Peter. I'd like to expand upon Peter's words just a bit. Juvenile Swainson's Hawks do not sport a translucent panel, which our quiz bird exhibits, though it has been reduced in breadth by the dropping of four inner primaries on each side and the growth of two adult inner primaries on each side. In fact, those replaced primaries make as good a case as any against Swainson's Hawk as they are not dark enough and are too-obviously banded. They also make a strong case against Gray Hawk, as adult Gray Hawks have a thin subterminal black band, not the wide virtually-terminal band on our quiz bird. Additionally, juvenile Gray Hawks tend not to sport the wrist commas of our quiz bird (created by individual spots on the underside primary coverts) and have rounder wingtips, with the longest primary not all that much longer than the outermost primary. Juvenile Red-shouldered Hawks have generally dark throats; even Florida juvs would show more dark here than does our quiz bird.

The quiz picture of a molting one-year-old Broad-winged Hawk was taken by Debbie Barnes at Fountain Creek Regional Park, El Paso Co., CO, on 28 May 2007.

Incorrect species provided as answers:
Gray Hawk - 4
Swainson's Hawk - 3
Red-shouldered Hawk - 2

Congratulations to the 9 of 18 getting the quiz correct:
Tyler Bell
Thomas Hall
Pam Myers
Margie Joy
Su Snyder
Peter Wilkinson
Robert McNab
Diane Porter
Chishun Kwong

Answer: Broad-winged Hawk)