Western Canada and western United States. Migrate south through Central America around March / April to winter in the central Andes of South America. Vagrant to western Europe.
Breeding females are mostly grey and brown above, and white below. Reddish neck and reddish flank patches.
Males have a brown back and lack the reddish patches, or these are reduced in size.
Straight, thin, black bill. Lobed toes.