They have a large spatulate bill. The breeding drake has an iridescent dark green head, white breast and chestnut belly and flanks. In non-breeding (eclipse) plumage, the drake resembles the female. The female is a drab mottled brown like other dabblers, with plumage much like a female Mallard, but easily distinguished by the long broad bill, which is gray tinged with orange.
These ducks are common in lakes here in Belgium in the winter and spring. the specimens in the picture live all year long in Het Zwin (vogelreservaat).