Attractive ground-dwelling bird. Slender and long-tailed, bright yellow below with paler throat and grayish-olive back; extremely variable. Tail is black with white outer feathers; often pumps tail up and down while walking on the ground. Young birds lack yellow color, but have distinctive head pattern. Often seen near water. Listen for high-pitched, piercing call note. Common breeder on Arctic tundra from Alaska to Russia; found in grassy and waterside habitats in Southeast Asian wintering grounds and in migration.