Mergellus

Mergellus is a genus of ducks in the family Anatidae. The genus currently contains only one living species, Mergellus albellus, commonly known as the smew. Historically, the genus has been used to encompass other species, but modern classification generally restricts it to the smew. The smew is a small sea duck with a distinctive appearance. Males are striking, with black and white plumage, a white crest, and a black bill. Females and young birds are more subdued, with grey and white plumage and a less pronounced crest.

The smew is found across northern Europe and Asia, breeding in forested wetlands and tundra. They migrate south in winter to more temperate coastal areas, often preferring sheltered bays and estuaries. Their diet consists primarily of small fish, crustaceans, and aquatic insects, which they catch by diving. Mergellus albellus is known for its diving ability and is a proficient underwater hunter. Despite their widespread distribution, smew populations have faced declines in some areas due to habitat loss and disturbance. Conservation efforts are in place to protect their breeding and wintering grounds. The genus name "Mergellus" is a diminutive of Mergus, a genus of mergansers, reflecting the smew's somewhat similar appearance and diving habits.