Monday, December 3, 2012

Quiz #477 (2012-4-09) Solution

Click on picture(s) for a larger view.

Solution by Tony Leukering

I know the quiz picture is tricky when the number of incorrect species provided as answers approaches the number of correct responses, and this quiz is an excellent example of such. The six incorrect species are of six genera in four families in three orders.

The size of the bird in the image is purposefully quite small in order to eliminate small-scale features visible. That is because most birds are not seen well enough in the field to discern such features, particularly this species. From the wave action, we can make the assumption that the water body is large, which should have us keeping pelagic species in the back, at least, of our minds.

The tubby body and large, rounded head rule out a large number of waterbird options, including some of those ruled out by other features. These other features include the bird's small feet and gray sides, which eliminate loons from consideration. Those same gray sides rule out various petrels and a number of the alcids, including murres, murrelets, and puffins. The unpatterned wings rule out most ducks. Looking closely at the head, we can see two critical features:  the white eye and the pale base to the bill (see expanded version of photo quiz, below).
 Among ducks, only Surf Scoter has whitish eyes and unpatterned wings, but only in males, and this is obviously not a male Surf Scoter. In fact, that bird's pale eye now reduces the options to just a few species of auklets. The gray sides, again, help here, as they rule out Least Auklet. The quiz bird's bill is too substantial to be that of Whiskered Auklet, while Crested Auklet is eliminated form the possible solution set by the extensive amount of what appears to be whitish plumage. Parakeet Auklet is ruled out by the lack of a white behind-the-eye eyeline. That pale base to the bill makes for positive (rather than negative, like the eyeline) determination for us. I took this picture of a Cassin's Auklet off San Diego, San Diego Co., CA, on 8 October 2011.

Incorrect species provided as answers:
Fea's Petrel - 1
Harlequin Duck - 1
Ancient Murrelet - 1
Black Scoter - 1
Pacific Loon - 1
Parakeet Auklet - 1

Congratulations to the 6 of 12 getting the quiz correct:
Logan Kahle
Ben Coulter
Tyler Bell
Donald Jones
Joshua Little
Richard Jeffers

Answer: Cassin's Auklet