Quiz #324 (2009-4-06) Answer

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Answer by Kevin Kerr and Tony Leukering

This week's two-bird quiz did not cause may problems for the regulars, nor for the few newer Mr. Bill Mystery Quiz afficionados. As Kevin Kerr provided a reasonable synopsis of the ID of the two not-so-wee beasties, I'll have him start us off.

"Assuming that I haven't missed something, I think that the identifications are actually fairly straightforward this week, despite the unusual appearance of two overlapping birds. The lower bird is a typical Black Vulture, thus the challenge is to identify the upper bird, whose body is mostly hidden. Luckily, there are lots of clues. The bird clearly associates with Black Vulture, is comparable in size to a Black Vulture, but has relatively pale wing and tail feathers, and with a longer, rounded tail. These features point pretty clearly to Turkey Vulture. Most other dark raptors would feature a banding pattern onthe tail and would be of noticeably difference in size."

Thanks, Kevin.

At this point, I wish to do two things: 1) emphasize Kevin's point about the differing tail shapes and colors (long, rounded, and paler -- with the tail contrasting fairly strongly with the blacker undertail coverts -- in TV, short, square, and blacker -- no contrast to undertail coverts -- in BV) and 2) to elucidate the ID a bit further. While given good views of either species, the identification of these two vulture species is easy, odd lighting, distant views, and other negative impacts on views can lead the unwary down the wrong path. Except under the most backlit of conditions, the pattern of black and pale on the underside of the two is diagnostic, with the black/pale contrast being in the hand (the outer wing) and perpendicular to the wing in BV and the contrast in TV being parallel to the wing. Additionally, though a few respondents noted otherwise, the wing shape of the two species is fairly different, with BV having wider and shorter wings to TV's longer and narrower wings. Finally, the flap style of the two species is radically different, with TV exhibiting a long and somewhat ponderous wing flap and BV an almost comical quick, snappy, almost scared-to-fall-out-of-the-sky wing flap reminiscent of smaller accipiters. The relative wing lengths of the two species are the primary movers and shakers in the causes of these two very different wing flaps.

I photographed these two birds in West Cape May, Cape May Co., NJ, on 19 October 2009 gliding off a thermal. I provide the next picture in sequence, below, as proof positive of the two IDs. of course, if Lesser Yellow-headed Vulture had been on the ABA-area list, the ID of the top bird would have been just a wee bit more difficult!



Incorrect species provided as answers:
Chihuahuan Raven - 1
Ferruginous Hawk - 1
Zone-tailed Hawk - 1

The 18 of 21 providing the correct answer:
Aaron Brees
Kevin Kerr
Al Guarente
Nick Komar
Bryan Guarente
Louie Toth
Marcel Such
Peter Burke
George Cresswell
Margie Joy
Joel Such
Mark Dettling
Peter Wilkinson
Su Snyder
Bob Archer
Jennifer Vieth
Joe Bens
Chishun Kwong

Answer: Black Vulture, Turkey Vulture

Quiz #323 (2009-4-05) Answer

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Answer by Tony Leukering

This week's quiz bird is dark above other than some white on the uppertail coverts and buffy-white fringing to most of the wing feathers. We don't really have much help here in determining the bird's underparts color, but embiggening (thanks, Homer) the picture enables me to see a sliver of the bird's right side and that area looks whitish. The wings also look quite long, but the secondaries look fairly short, as they're mostly covered by the greater coverts. One foot looks somewhat pinkish, but the other looks blackish -- lighting?

The two geese provided as answers by respondents would show much more white at the back end of the body and would not show unmarked white sides. The lack of mottling or other internal markings on the wing coverts rules out virtually all of the gull options and the white side rules out the remaining gull option, Heermann's Gull. Jaegers would be another good group to consider, but even Long-tailed Jaeger should show at least some bright white primary shafts among the outer primaries and the shafts of all or most primaries in all three jaeger species are noticeably paler than those on our quiz bird, though they may not be white. With various larids excised from consideration, we really have no good options outside the Procellariiformes, the tubenoses.

"Ugh," one might say, as most of us don't see those things anywhere nearly often enough to be able to nail this bird going away. But, it's not all that difficult to work through the field guides to the correct answer. I mean, only about 50 species have occurred in the ABA area! And if that's not enough to make one cheer with abandon, we can do some wholescale deletions from that list. First off, we can remove the storm-petrels from consideration -- they don't have the wing length or the plumage pattern exhibited by our quiz bird. That's 13 down. Most albatrosses don't show our bird's topside plumage pattern and all of 'em have even longer wings than does our quiz bird; another eight down. Of course, now that we're into the Procellariidae (petrels and shearwaters), we're into a fairly difficult group, and one that accounts for the remaining 29 ABA-area tubenose species!

Even now, though, we can conduct large-scale removals, and we'll start with all of those species that are not both evenly-dark above (there's little suggstion of the typical Procellariid 'M' on our bird's wings, but it could still be present if it were not particularly contrasty, given the angle of the photo) and with white sides. If we also use our bird's thin white uppertail-covert band as a decision character, then we're left with very few possibilities. In fact, there are so few options that we have actually arrived at our answer: Greater shearwater. At this point, one might opine that it would be nice to be able to use some positive characters to ID our bird, rather than simple process of elimination. Ah, but we have. Our bird's thin white uppertail-covert band is a particularly good field mark for the species. Black-capped Petrel sports a much wider white band proximal from the tail and neither Cory's nor Cape Verde shearwaters are so dark above, nor do they have white sides. Northern Fulmars with white bands proximal to the tail are paler above with obvious pale wing panels.

I provide another view of the same bird, below, an individual that I photographed off southern New Jersey on 21 October 2009.



Incorrect species provided as answers:
Wilson's Storm-Petrel - 1
Black-footed Albatross - 2
Parasitic Jaeger - 1
Black-tailed Gull - 1
Brant - 1
Canada Goose - 1

The 13 of 20 providing the correct answer:
Peter Wilkinson
George Cresswell
Aaron Brees
Bob Archer
Tyler Bell
Mark Dettling
Margie Joy
Peter Burke
Kevin Kerr
Joe Bens
Marcel Such
Joel Such
Chishun Kwong

Answer: Greater Shearwater