Monday, November 7, 2011

Quiz #424 (2011-4-06) Solution

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Solution by Tony Leukering and Peter Wilkinson

As noted by Christian Nunes, one of the best clues to this week's quiz bird's identity was provided by the substrate. The smooth bark with the yellowy-green cast makes the tree identifiable as an aspen. From there, we'll go to some of Peter Wilkinson's thoughts on the bird:

"Those flank feathers reduce it to an Otus owl pretty quickly, so we have Flammulated and the three screech-owls, Whiskered, Eastern, and Western" [though the A.O.U. now considers the screech-owls to belong to Megascops, while Flammulated still resides in Otus].

I agree with the above and note that all ABA-area nightjars can be eliminated by the fact that the wingtip that we can see well extends well past the tail tip and because of that flank-feather pattern (with a strong black shaft streak crossed by weaker blackish bars). Back to Peter.

"I think that you can eliminate Whiskered as it apparently doesn't have a rufous morph and this bird clearly has at least a little rufous in the wings."

Again, I agree. The hint of rufous can be see in the primary coverts of the left wing. Peter.

"After that I haven't a clue. I've gone for Flammulated as:
- apparently even gray ones still show traces of rufous in the wings;
- the morphs of the others, while intergrading, don't seem to be as contrasty as this bird; and
- that way, I don't have to worry about hyphenation and capitalisation of screech-owl (though, come to think about it, that's probably why you set this one).

Only one respondent (Josh Parks) noted the key feature in separating Flammulated Owl from the screech-owls and it has to do with migration. The three screech-owls are residents, with individuals dispersing short distances, but undertaking no regular migration. Flammulated Owl is a fairly long-distant migrant, with the species emptying out of the ABA area to winter south of the border from central Mexico to Guatemala. In most groups of related birds with differing migration strategies, with all else being equal, the migrant species/subspecies will have relatively longer wings than will the resident forms (and, extending the argument a bit, longer-distance migrants will have relatively longer wings than will shorter-distance migrants within the species). Flammulated Owl sports relatively longer wings than do its resident congeners, except that Whiskered Screech-Owl also has relatively long wings. On Flammulated and Whiskered, the wingtips extend well beyond the tail tip, while on Eastern and Western, the wingtips typically fall short of the tail tip, though with some having them extend just beyond the tail tip.

As far as the three screech-owl species, all are relatively low-elevation species, with Whiskered associated most often with oaks, while Western and Eastern screech-owls are typically species of riparian habitats or other habitats with broad-leaved tree species. Yes, both species are found in other habitats, but, in general, they are most widespread and common in the habitats that I've noted; aspen is found higher than are the habitats that most Eastern and Western screech-owls utilize in either or both of elevation and latitude. Flammulated Owl is considered by some to be an inhabitant of older seral stages of conifer forest, particularly Ponderosa Pine. However, in my experience, the species is most closely associated with aspen. That is because most woodpecker species within the breeding range of Flammulated Owl seem to be associated with aspen when nesting. That is because it is easier on woodpeckers to construct cavities in aspens than in any other species of tree in their ranges. Flammulated Owls use woodpecker cavities for nesting, so....

Tree species and relative wing length prove the case for this Flammulated Owl photographed near San Isabel, Custer Co., CO, 11 June 2011 by Brandon Percival.

Incorrect species provided as answers:
Western Screech-Owl - 3
Eastern Screech-Owl - 3
Common Poorwill - 3
Whiskered Screech-Owl - 2

Congratulations to the 8 of 19 getting the quiz correct:
Thomas Hall
Kirk Huffstater
Christian Nunes
Josh Parks
Sean Walters
Peter Wilkinson
Bryan Guarente
Joel Such

Answer: Flammulated Owl