Female Mallard vs. American Black Duck.

Flock of Mallards and an American Black Duck

Mallards and American Black Ducks can be very hard to tell apart, except for male Mallard in breeding plumage. Otherwise the females and male mallards in eclipse plumage, a very similar in appearance. One item that helps separate them is the colors that border of the blue speculum. Mallards speculum is boarded in the front and back by white while American black duck speculum has no white borders. Also, the female Mallard tail feathers are strongly edged in white. I hope this helps you in the field, to identify the differences in these species.

Flock of Mallards and an American Black Duck with ID Marks

American Black Duck

Hen Mallard