Body length: 65 cm. Wingspan: 120 cm. Plumage: has seasonal and age dimorphism. The adults in winter have dark brown upperparts and white underparts. Bright plumage in summer; head velvety pale grey and neck black with black and white stripes at sides. Juveniles resemble the adults in winter. In all adults forehead steep with peaked forecrown in profile, the back raised at its front-side, the bill is dagger-shaped. Biotope: mainly seashores, rarely larger inland water basins.