Monday, May 23, 2011

Quiz #400 (2011-2-08) Solution

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Solution by Tony Leukering

Three individuals this time, with at least two species present: a woodpecker and a thrasher. Or two thrashers. As at least one respondent noted, identifying the "easier" bird -- the woodpecker, may help us ID the thrashers, so let's head down that road. The woodpecker is one of the zebra-striped beasts, but one with an odd tail pattern, a feature that some may have noted as critical. That pattern includes a mix of entirely black feathers and black-barred white feathers. While we might consider female Williamson's Sapsucker, that species doesn't sport quite the regular black-and-white barring exhibited by the quiz woodpecker. Additionally, they usually sport a vague superciliary and always have dark flanks (unlike our bird's paler flank). Additionally, the quiz woodpecker has the central rectrices barred, not solidly black, as in Willy Sap. In fact, that pattern of all-black middle rects on each side but with all other rectrices barred also rules out Golden-fronted Woodpecker, which has an all-black tail except for the barred outermost rectrices. Red-bellied Woodpecker has a similar tail pattern to that of our quiz bird, but that species sports some red or orange on the head in all plumages -- something that our quiz woodpecker lacks.

So, does an ID of Gila Woodpecker help us with the thrashers? In that vein, the various species that might jump out at us as good possibilities all are sympatric with Gila Woodpecker. Ah, well. Both thrashers have longish and obvious curvature to their bills, ruling out Sage Thasher immediately and, with consideration of photographic angle, Bendire's Thrasher. Yes, the left thrasher's bill may look shorter than that of the right thrasher, but, the left one is facing at least somewhat toward us, so its bill is foreshortened. Despite that, we can see the distinct kink in the bill, compared to the short and evenly-curved bill of Bendire's Thrasher.

The really streaked thrashers are right out for both thrashers and the left one cannot be either California or Le Conte's, because it sports a pale eye. Crissal Thrasher is ruled out for that species as well, for a number of reasons, one of which is that the bird lacks distinct and black lateral throat stripes and another is that it lacks an obviously red crissum. The vague grayish-brown spotting heaviest on the chest and with a vaguely paler belly than chest suggest that this bird is referable to palmeri Curve-billed Thrasher (the western form). With those features in mind, glancing back at the right thrasher should point us in the same direction. While we might have considered Crissal for that one (we cannot see either its eye or vent colors), that vague spotting underneath rules that option out, as does the brown aspect to the underparts coloration (rather than the medium gray of Crissal).

One last note about Curve-billed Thrasher: the two ABA-area subspecies are usually separable by plumage and have differing vocalizations and the species is a good candidate for splitting. Thus, it behooves us all -- particularly those looking at out-of-range Curve-bills -- to pay attention to which is which. I took this picture of a female Gila Woodpecker and a pair of Curve-billed Thrashers at the San Xavier Mission, Pima Co., AZ, in January 2007.

One respondent submitted an answer with only one species. Also, one respondent neglected to capitalize the 't' in 'Thrasher.'

Incorrect species provided as answers:
Crissal Thrasher - 1
Bendire's Thrasher - 3
Williamson's Sapsucker - 3

Congratulations to the 17 of 25 getting the quiz correct:
Kirk Huffstater
Christian Nunes
Margie Joy
Pam Myers
Nick Komar
Robert McNab
Peter Wilkinson
Barbara Deneen
David Such
Chishun Kwong
Christopher Hinkle
Diane Porter
Marcel Such
Adrian Hinkle
Joel Such
Bryan Guarente
Burke Angstman

Answer: Gila Woodpecker, Curve-billed Thrasher