This image shows nicely the size difference and coloration difference between American Goldfinches in winter plumage
and female Lesser Goldfinches. The Lesser Goldfinch is definitely a smaller bird, has yellower feathers on the back and belly than does the
American Goldfinch. The American Goldfinch has a much stronger contrast in his black and white wing bars,
tends to have a yellowish throat and whitish belly and tawny brownish feathers on his back.