Thursday, 5 March 2015

B.O.T.D. Gray-Crowned Rosy-Finch

Gray-Crowned Rosy-Finch (Leucosticte tephrocotis)

From high on a  Colorado mountainside, a single call note sounds. It hangs momentarily in the cold, thin air at 12,000 feet, then plummets into the valley below. Following close behind is a rippling folk of dark-bodied finches. Pale wings flash in the sunlight as the land at the edge of a snowfield and begin to feed. There is no mistaking the birds for anything but the rosy-finch, which thrives in the tundra of  high elevations.

Not long ago an observer in the Rockies might have had difficulty identifying the feeding birds. Before 1983 the American Ornithologist's Union recognized three species of rosy-finch in North America: the wide-ranging gray-crowned rosy-finch, and the more localized brown-capped and black rosy-finches. Despite differences in range and plumage, the three birds are now regarded as subspecies of a single one: the Rosy-Finch

Taxonomy is a tidy science but hardly interpretation-free. The line between a species and a subspecies is often a fine one, with classifications made on the basis of supporting evidence. Because of new evidence, and a recent fundamental shift in the way scientists classify birds and other creatures, there is reason to believe that the three rosy-finches will once again be split into three separate North American species. This will make identification more difficult - but more interesting too.