Monday, February 9, 2009
Click the picture for a larger view.
Answer by Tony Leukering
This week's quiz was a bit tricky for two reasons. All respondents got correctly to the geese, but many went adrift after that, as both the second-from-the-left bird and the rightmost bird caused folks problems. And, of course, those two birds are the reason behind my usage of this picture that I took at John Martin Reservoir, Bent Co., CO, on 16 December 2008. Aaron Brees provided a good analysis from the Snow vs. Ross's side, and I'll have him start us off.
"Four Chen geese. The left most bird is clearly a white adult Snow Goose. The next bird is a dark/intermediate immature Snow Goose. The lack of an extensive white vent rules out an unlikely immature dark Ross's and seems to make identifying the white bird on the right possible. The third bird is a dark adult Snow Goose. And the bird on the right is potentially the tricky one. I can't find any structural differences between it and the other white bird that I can't attribute to size difference between the two. The bill on the right bird looks proportionally the same as the other three birds. Being the same structurally and the same size as the immature Blue Goose, this is presumably another Snow Goose and not a Ross's, which should appear significantly smaller. My guess is that birds 1 and 3 are males and the two smaller birds are females, explaining the size difference."
Thanks, Aaron. For those that got fooled by the goose second from the left, the bird does appear fairly white-cheeked goose-like. However, that bird's head is mostly pale, rather than black with a white patch extending from the chin to behind the eye. Also note that both dark-morph birds lack the strongly contrasting white vent region of both Canada and Cackling geese (white-cheeked geese).
Four respondents' guesses were precluded from being correct for the competition, as they were submitted either in the plural (n=3) or lacking a capital in the second word (n=1).
Tallies of incorrect species provided in answers:
Ross's Goose - 9
Cackling Goose - 4
Canada Goose - 1
Greater White-fronted Goose - 1
The 20 of 34 providing the correct answer:
Answer: Snow Goose