Apparent Neotropic Cormorant. I don't know if the video grabs can rule out a hybrid. More size comparisons at bottom of page. The bird showed a very acute angle to the rear of the gular pouch, and no orange on the lores. Pouch was yellow-orange, not as bright as on the Double-crests. Scapular feathers were more elongated and pointy than on immature Double-crests.
Video grabs (Sony video camera through a Questar) and digiscoped photos25-30 OCT 2005, Potomac River, Montgomery Co. MD. Dave Czaplak
A glimpse of the bird flying through the trees.