Small, compact duck with a long, fan-shaped tail, often held sticking up out of water. Breeding males have a chestnut body, black head, and baby-blue bill. Nonbreeding males and females are variably brown overall, often with a smudgy dark face and a dark line through the cheek. Occurs in pairs or loose flocks, bobbing like corks on lakes in the Andes from central Colombia to southern Chile. Dives to forage on aquatic invertebrates. Not often seen flying.