Small, compact duck with a long, fan-shaped tail, often held sticking up out of water. Breeding males have a chestnut body, black cap, white cheek, and baby-blue bill. Winter males have a brown body, black cap and white cheek. Females and immature males are brown overall with a dark cap and dark line through the cheek. Often in tight groups bobbing like corks on ponds and bays. Dives to forage on aquatic invertebrates. Not often seen flying.