The corner of Harborplace formed by the two main pavilions is a hangout for these dabbling ducks. They're always looking for a handout from us humans, and they're worth it, as they provide a lot of free entertainment.
This one didn't seem bothered by me at all as I took over a dozen photos up close and personal, down on the deck with my Canon A620 - the articulated LCD is great for this sort of thing.
The green in the background is the historic frigate USS Constellation.
By the way, I can't quite figure this duck out. It looks like a female Mallard, but the beak is yellow, rather than orange and black, and I didn't think the females had any green on their heads. If you know from ducks, please enlighten me.