The Common Merganser is a large, fish-eating duck found throughout North America, parts of Europe and Asia. They are easily distinguished by their long, serrated bills and crested heads. Male Common Mergansers have green heads with white bodies and black backs, while females have gray-brown bodies with rusty heads. They are skilled divers and use their webbed feet to propel themselves underwater. These ducks are monogamous and nest in tree cavities or old woodpecker holes near water. Common Mergansers are also commonly hunted for sport and have been affected by habitat loss and pollution.