Monday, September 17, 2012
Solution by Tony Leukering
We've got two birds this week apparently attacking thistle heads for sustenance. Just that fact could send us straight to the cardueline finches, which are so fond of thistles. But, let's do things thoroughly. The tiny piece of bill of the upper bird does not give us much with which to work to identify the family to which our quiz birds belong, but that bill tip does not look particularly thin. However, the very blackness of the wings of both birds, the lack of streaking throughout, and the very long primary projection really rule out all warbler options. Since our birds are quite small, there aren't many other options, as vireos are ruled out by the lack of any distinct head pattern, so we'll head to the back end of the field guide to figure out which finch.
The birds' size, overall plumage color, and lack of streaking limit us, really, to just three options: Lesser and American goldfinches and Common Chaffinch. Lesser Goldfinch can be ruled out by the combination of very black wings and bright white vent region. The dullest of Lessers can have white vent regions, but those are young females, which sport fairly brown wings. That is, males of these species have obviously black wings, while females tend to have dull blackish or brown wings that do not contrast so strongly with the white wing bars. Additionally, any black-winged Lesser Goldfinch should show much more white at the base of the primaries and most such birds would have yellowish vents. The same wing features that rule out Lesser Goldfinch also rule out Common Chaffinch, with males sporting an almost triangular lower wing bar with a connection of white to the upper wing bar. Females, which have browner wings, also tend to have the upper wing bar more yellowish and also tend toward a thin, but distinct dark postocular stripe. I took this picture of two male American Goldfinches at Pueblo Reservoir, Pueblo Co., CO, on 18 December 2004.
One respondent's otherwise correct answer included an incorrect assessment of sex directly with the species guess, thus was considered incorrect; please read the rules about this facet.
Incorrect species provided as answers:
Common Chaffinch - 1
Lesser Goldfinch - 1
Congratulations to the 17 of 20 respondents getting the quiz correct:
William von Herff
Answer: American Goldfinch