Sources
Birds of Eastern and Central North America (Peterson Field Guides) by Roger Tory Peters
http://animals.nationalgeographic.com/animals/birding/american-goldfinch?source=A-to-Z
http://www.allaboutbirds.org/guide/American_Goldfinch/id
http://web.colby.edu/mainebirds/2010/09/01/american-goldfinch/
http://animals.nationalgeographic.com/animals/birding/american-goldfinch?source=A-to-Z
http://www.allaboutbirds.org/guide/American_Goldfinch/id
http://web.colby.edu/mainebirds/2010/09/01/american-goldfinch/