Bluebill :: Bluebill (n.) A duck of the genus Fuligula. Two American species (F. marila and F. affinis) are common. See Scaup duck.
Bluebird :: Bluebird (n.) A small song bird (Sialia sialis), very common in the United States, and, in the north, one of the earliest to arrive in spring. The male is blue, with the breast reddish. It is related to the European robin..