[Mystery bird] American Goldfinch, also known as the Eastern Goldfinch or the Wild Canary, Spinus (Carduelis) tristis, photographed on the Brazoria Wildlife Refuge, Brazoria, Texas. [I will identify this bird for you in 48 hours]
Image: Joseph Kennedy, 5 January 2010 [larger view].
Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/320s f/8.0 at 1000.0mm iso400.
Please name at least one field mark that supports your identification.