[Mystery bird] Double-Crested Cormorant, Phalacrocorax auritus, photographed at Hermann Park, Houston, Texas. [I will identify this bird for you in 48 hours]
Image: Joseph Kennedy, 23 December 2009 [larger view].
Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/500s f/8.0 at 1000.0mm iso400.
Please name at least one field mark that supports your identification.