Not convinced these are mallard!

They were in a group of about 15 to 20. They have the "mallard" bill, feet, and greenish head. Their body does look a little darker than most mallards. Mallards have been known to cross breed with other ducks.

Didn't know about the cross-breeding thing... that's probably what we're seeing. "Classic" mallard colour is a greenish head, but with a well-defined change of colour to the breast colour, usually with a definite white collar. Colours we see here blend into each other, and no visible sign of a collar.

More importantly, they're very pretty -- nice photo!

Mallards most often interbreed with black ducks, which are darker and don't have the well defined color areas.I bet that's what these are. They are pretty, though and this pic gives us a nice sense of their everyday activities, which I like.