15 cm (6") Fairly common in summer in high arctic from Alaska to northeaster Canada; rare elsewhere. Conspicuous white rump. Distinctive flashy tail; white with a dark central and terminal band. Small active upright bird with tail fanning and constant bobbing habit.
Male: gray above; white with buff below; black face mask and black wings.
Female and Fall Male: brown above with brown wings and no face mask; buffy below.
Song: harsh "chak-chak".