Definition of "canvasback"

Yesterday, I received a great present from Mr. Webster, from Washington; a large basket of canvasback ducks and a large turkey.

1857 The Private Correspondence of Daniel Webster

The native State of Patrick Henry Hanway was a moss-grown member of the republic and had been one of the original thirteen. It possessed with other impedimenta a moss-grown aristocracy that borrowed money, devoured canvasbacks, drank burgundy, wore spotless tow in summer, clung to the duello, and talked of days of greatness which had been before the war.

1904, Alfred Henry Lewis, “How a President is Bred”, in The President: A Novel, New York, N.Y.: A[lfred] S[mith] Barnes and Company, page 24