Body length: 35 cm. Wingspan: 63 cm. Plumage: has seasonal and age dimorphism. Adults: after breeding season the upperparts of the body are dark brown and the underparts white. The cheeks and sides of the neck have rusty patches in summer, the head crown is black. The bill is straight. In summer plumage is bright. Juveniles resemble the adults in winter. Biotope: in small flocks at seashores or close-to-seashore water basins.