Monday, July 16, 2012

Quiz #458 (2012-3-03) Solution

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Solution by Tony Leukering

A bird flies over your head flying away and you have scant time to assess the bird's features. Unfortunately, this is not a video clip, as flight style would help tremendously in winnowing the choices, but, alas, we are stuck with this static picture. We get a strong impression of a long, dark tail with an extensive white tip; whitish underparts; and a white trailing edge to the secondaries. These three cues leave few species to fill a possible solution set, which might include White-winged Dove, Northern Shrike, and Blue Jay.

Close scrutiny of the tail tip might allow us to determine that the white tip does not extend across all rectrices, as the central two are dark-tipped. Unfortunately, that does not reduce the number of options, as all three solution-set members have the same pattern. We might note that the central pair of tail feathers (rectrix 1 -- or r1 -- on each side of the tail) are slightly longer than the rest and protrude a wee bit beyond the tips of the adjacent pair (the r2s). This feature could be useful as long as we know that it's not due to some ephemeral posture that the bird was in when the picture was snapped. However, the tail tip does provide us another clue: each succeeding pair of rectrices from r2 to r6 has a more-extensive white tip than does the previous. White-winged Dove has, essentially, the same amount of white on each white-tipped feather. Finally, the white trailing edge to the secondaries is much more extensive than shown by any Northern Shrike.

I took this picture of a Blue Jay overhead at Cape May Point, Cape May Co., NJ, on 7 May 2011. Other clues that we might have used include the dark feet (ruling out doves) and, as noted by Thomas Hall, the bluish aspect to the upperside of the bird's right wing.

One respondent provided two different answers; I accepted the most-recent one as that person's official response; unfortunately, incorrect.

Incorrect species provided as answers:
Clark's Nutcracker - 1
Lark Sparrow - 1
White-winged Dove - 1
Eastern Kingbird - 1
Black-billed Magpie - 1

Congratulations to the 14 of 19 getting the quiz correct:
Ben Coulter
Tyler Bell
Richard Jeffers
Al Guarente
Margie Joy
Logan Kahle
Thomas Hall
Su Snyder
Pam Myers
Robert McNab
Bryan Guarente
Josh Yoder
Sean Walters
Chishun Kwong

Answer: Blue Jay