Eiders are bulky ducks with a large wedge-shaped bill. In fact, it is their bill and their flattened head that make them easy to identify. Males are unmistakeable with their black-white plumage and characteristic 'ah-hoo' call. Downy feathers from eiders are the best in the world. Females line their nests with this material. In Iceland, people gather the feathers for making comforters and pillows.