On one of our trips to Yellowstone I had the opportunity to photograph a few Cassin's finch. I almost missed out because at first I thought they were house finch. House finch are pretty common through out most of the United States. But house finch have more streaking on the belly which this bird obviously does not have. Next I was thinking purple finch but Yellowstone would be a bit out of their range. It also has that distinctive red crown, a by product of the carotenoid pigments that are found in the colorful berries that they like to eat. The purple finch has a more uniform red color on the head. I finally identified the birds as a Cassin's finch, which were named after famous ornithologist John Cassin, who first recorded them in the 1850's while part of the Pacific Railroad Survey. Cassin's finch breed in the western third of the US and winter in the Pacific southwest and Mexico.