Tern: help with I.D. please.

I keep going to back to roseate tern, but could be arctic, or even common. Any help appreciated. Taken near Deer Island in the Bay of Fundy on Aug, 27, 2008.

http://theridgerunner.com/edspics/acadia/IMGP3592.jpghttp://theridgerunner.com/edspics/acadia/IMGP3596s.jpg
thanks!
ed

To me this is more suggestive of a non-breeding plumage Bonaparte's Gull. Tern's have forked tails (somebody correct me if there is an exception or two to this)

I agree with Daniel, looks like a Bonaparte's Gull to me, too: http://www.birds.cornell.edu/AllAbou..._Gull_dtl.html

Thanks, you guys! I had considered that it was a gull because of the tail, but had no idea where to start with I.D. (not proficient with gulls!)

regards,
Ed

Got it in one as they say. I study the ecosystem in the area of Deer Island and of course see Bonaparte's Gulls frequently in the late summer/fall. They stopover in the area to feed mainly on krill, which is a shrimp-like animal in the family Euphausidae (penguins feed on a related species in Antarctica). Krill are brought to the surface and made available to gulls by the strong upwellings in the area that are driven by the strongest and highest tides in the world in the Bay of Fundy. I live at the head of the Bay and we get tides in the region of 12-18 metres or 40-60 feet depending on the time of year and phase of moon.