Mallard

At this time of year, mostly-grown youngsters are a definite possibility.

Scott, I will keep that in mind about the bill color. After I posted, I thought they might be juveniles as well. You know, like how male and female Cardinal juveniles look like mature female cardinals minus the lack the orange beak of a mature female.

Female mallards have orangish bills with a black covering, like the one in the center of the second picture, while males have a greenish yellow bill. After breeding season all mallards molt, the males starting earlier, and develop their non-breeding, or eclipse, plumage. The one in the first picture is definitely a molting male, as it looks pretty ratty but still has traces of green on its head. Since they lose all their feathers over a short period of time they become very quiet and shy, since there are times during the molt when they can't fly.

They look like female mallards. Anas platyrhynchos " The Mallard is the ancestor of all domestic ducks, and can interbreed with other species of genus Anas.[1] However, a potentially terminal side effect of this vast interbreeding capability is gradual genetic dilution, which is causing rarer species of ducks to become at risk for extinction." - Wikipedia I"m not sure if these are interbred or just molting as ScottRasmussen suggests. They look like pretty straight forward female Mallards to me. I'm not super knowledgeable on Mallards though.

They look like molting mallards. It's definitely that time of year here in New England.