Having been amazed at your American Goldfinches, I thought I would share this image of a British Goldfinch taken several years ago in the age of the Canon 10D.
Canon 10D, with 100-400 IS lens used at 400mm, photograph taken from a garden hide.
Exp 1/90th @ f8, ISO 200
Beautiful capture of this handsome bird! If they come to this perch frequently I would remove the teasel heads below the main one to isolate just the one head of teasel for a perch. Gorgeous bird!