Size: L: 60 cm. Wt: 350-400g. Males and females similar.

Breeding: body white, with plumes on head, neck, and back; slender black bill; legs black; feet yellow. Note: in high breeding plumage, feet and lores turn red-orange.

Winter: plumes shorter; feet paler.

Juvenile: plumes absent; backs of legs yellowish-green; feet yellow.