You can't see from the photo that they're smaller than mallards, but you can see that they have no speculum, and their bills are too dark for mallards. Here's the Wikipedia article on gadwall, where you will see that the female looks a lot like a female mallard, but with no speculum.
![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
(no subject)
Date: 2007-05-11 07:37 am (UTC)