Northern Shoveler - Anas clypeata

In September the ducks return to the San Francisco Bay Area in good numbers, but most will be starting molting from their cryptic eclipse plumage into the bright breeding plumage they wear most of the year. Juvenile ducks and male duck in eclipse plumage often strongly resemble the adult female, so identification can be a challenge.

The Shoveler shown here was seen on Sept 17 at Las Gallinas. I figured it was a female Northern Shoveler, but several features suggest it may well be a male in eclipse plumage. The yellow-orange iris is similar to the bright yellow in the adult male, whereas juveniles and females have a browner iris. The head is a dark gray, while females and young shovelers would be more brown. The chest, breast and flanks on this birds have an attractive rufous wash, unlike the muted browns seen on females and youngsters. Bill color much like a female's, but the male's bill will only become black in full adult breeding plumage. So I'm going the an adult male in eclipse plumage.

Here's an older shot of a female. Note the brown iris and pale brown head.

Male Shovelers go through a more variable and prolonged molt than most other dabbler species, so most of them won't display the deep green-black head, rich chestnut flank color and striking white breast until late November.