The Common Merganser is a large duck species found in North America, Europe, and Asia. It is known for its slender body, long neck, and distinctive serrated bill, which helps it catch fish. Adult males have a striking green head, white body, and black back, while females are mostly brown with a reddish-brown head. These ducks prefer freshwater lakes and rivers, often nesting in tree cavities or on the ground near water. Common Mergansers are social birds, often seen in groups, and they primarily feed on fish, making them skilled divers. Their population is generally stable, but habitat loss can impact their numbers.