Quiz #461 (2012-3-06) Solution

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Solution by William von Herff and Tony Leukering

It was obvious to respondents that this week's quiz bird was a juvenile accipiter, and as is often the case with this genus, answers ran the gamut of possibilities. Quiz newcomer William von Herff provided an excellent analysis of the bird, so I'll start with his take and finish up with some minor additional notes. William?

"Ah, a perching accipiter! And a headless one at that! Oh joy! Anyway, you can get to accipiter because of the slim size, the streaks on the underside, and the barred tail. As well, the streaks mean that it's a juvenile.

"So, now we have to differentiate the three accipiters. Well, it's a juvenile, and you can notice that it has what appears to be a clean vent and undertail coverts. Northern Goshawk would have scattered teardrop-shaped splotches on the vent and undertail coverts and a much more broken and scattered under tail pattern, compared to that of the quiz bird.

"So, on to the Sharpie/Cooper's duo. Normally, we could just look at the head structure from this close up, but this bird is hiding its head shape, so we have to figure it out using other clues. So, let's look over some key ID points. The most well-known juvenile accipiter separator is the streaking: Cooper's has thin streaks that fade away around the belly area, while Sharpie has thicker streaks that go farther down. The quiz bird has thin streaks that fade away at the belly area, so this points to Cooper's. The trait is highly variable, though, so I'll give Cooper's 0.75 points (Sharpie: 0 Cooper's: 0.75). The second feature is shape: Cooper's has a very barrel-shaped chest, while Sharpie has a body shape that gets thinner as it goes down. The quiz bird, while it is at an awkward angle, looks very barrel-shaped. (Sharpie: 0 Cooper's: 1.75). Third of all, leg thickness: Cooper's have fairly thick legs, while Sharpies have pencil-thin legs. This bird seems to have thicker legs, so I'd give another point to Cooper's. (Sharpie: 0 Cooper's: 2.75). Next, there's the terminal band: This is very variable, so whichever gets this one, gets only a half-point. Cooper's has a fairly wide terminal band, while Sharpie has an extremely thin terminal band. The quiz bird seems to have a wide terminal band, so Cooper's gets a half-point (Sharpie: 0 Cooper's: 3.25). Then, there's the tail length: This is a very awkward angle, so I'm going to compare it to the length of the wing. On Sharpie, the wingtip ends at the end of the second band from the body, while in Cooper's, it ends at the very start of that band. In this bird, the wing ends at the start of that band, so another point for Cooper's. (Sharpie: 0 Cooper's: 4.25). Finally, tail shape: Cooper's tends to have a rounded tail, while Sharpie has a straight tail tip with two sharp corners. This bird seems to have a tail leaning more toward Sharpie, so a point for Sharpie. (Final score: Sharpie: 1 Cooper's: 4.25). Now, this duo has plenty of variation in every single aspect that I just mentioned, so that's why I thought it would be better to tally up the field marks, instead of doing elimination ID."

Thanks, William! Some other points that I wished to make on this one are that juvenile Northern Goshawk have very thin white bands bordering the dark tail bands that contrast paler both with the obviously dark bands, but also with the wide pale bands. My last comment is that I would probably have given Cooper's the whole point for tail shape because, though the tail is mostly squared-off, we can see the outermost right rectrix (it is misplaced to the middle of the tail) and it is obviously shorter and lacking a distinct corner at the outer edge of the tip (instead, the outer part of the tip is quite rounded). This is a feature that is diagnostic in differentiating Cooper's Hawk from Sharp-shinned Hawk. Steve Mlodinow took this picture of a juvenile Cooper's Hawk at the Shillapoo Wildlife Area, Douglas Co., Washington, in January 2011.

Incorrect species provided as answers:
Sharp-shinned Hawk - 2
Northern Goshawk - 1

Congratulations to the 17 of 20 respondents getting the quiz correct:
Tyler Bell
Al Guarente
Logan Kahle
Ben Coulter
George Cresswell
Su Snyder
Richard Jeffers
William von Herff
Bryan Guarente
Robert McNab
Margaret Smith
Josh Yoder
Peter Wilkinson
Nick Komar
Pam Myers
Joe Bens
Sean Walters

Answer: Cooper's Hawk

Quiz #460 (2012-3-05) Solution

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The picture is not of an ABA Code 5 species.

Solution by Tony Leukering

What's a day when one doesn't learn something? I like to avoid such days and, thanks to Peter Wilkinson, I have avoided that pitfall today.

This week's quiz bird is obviously a small gull (plumage and small, dark bill) and the caveat with the quiz photo precluded Gray-hooded Gull from being the solution. Once amongst the small gulls, we should check wingtip pattern to greatly reduce the number of options. In this view, we cannot see much of anything of the wingtip pattern, but we can see enough. The enough of which I write is the underside of the outermost primary (p10) on both wings and on both wings, those feathers are nearly entirely white. That means that this cannot be other than one of the species with white wedges in the wingtip. (As an aside, studying the underside of the wingtips in most gulls can be quite useful in arriving at an ID and one can usually manage such on a perched or swimming gull.)

Differentiating Black-headed and Bonaparte's gulls can be a mite tricky at times, but this view is not one in which it should be, and I note that no respondent went with Black-headed, though some missed the obvious separator. Bill color is often useful in discerning between the two species, dark reddish in the former, black in the latter. However, this color can be tricky to assess in some pictures and I would certainly be hesitant to rule out Black-headed on the strength of bill color on this picture! Throw in the difficulty in assessing mantle color (Black-headed's is paler than is that of Bonaparte's) and I would have been left with a single -- though excellent -- differentiating character. Our bird's nape is obviously gray; Black-headed sports a white nape (and crown) contrasting with the gray mantle.

This is where that new knowledge bit comes in. Peter Wilkinson pointed out that there is another clue, in the shape of the meeting of black tip and white body of p10 in the two species. Bonaparte's shows a smoothly curved meeting extending from the inner margin of the feather down toward the tip and to the outer margin of the feather (as on the quiz bird; see inset, below). With Peter's suggestion, I looked into the feature a bit and found that the meeting in Black-headed is rather straighter, cutting across the feather or, even, slightly back up the feather, such that where the white meets black on the inner margin is at the same distance from the tip -- or closer -- than where it meets on the outer margin. As Peter noted, I doubt that the character would be useful in the field, except under the most beneficial circumstances, but it seems to be readily assessable in photographs given an appropriate view.

I took this picture of an adult Bonaparte's Gull in North Cape May, Cape May Co., NJ, on 11 March 2010.

One respondent's answer was precluded from being correct for the competition as it neglected the "e" in the name of the species and another's was precluded as the "g" went uncapitalized.

Incorrect species provided as answers:
Ross's Gull - 1
Black-legged Kittiwake - 1

Congratulations to the 18 of 20 getting the quiz correct:
Ben Coulter
George Cresswell
Nick Komar
Logan Kahle
Tyler Bell
Margaret Smith
Robert McNab
Jim Nowjack
Al Guarente
Richard Jeffers
Josh Yoder
Su Snyder
Margie Joy
William von Herff
Peter Wilkinson
Kirk Huffstater
Bryan Guarente
Sean Walters

Answer: Bonaparte's Gull