Characteristic birds of open seas and oceans; they are frequent especially in the southern hemisphere of the Earth. Their species include sparrow-sized and goose-sized birds as well. They visit the coasts only in the breeding season; most of their lives is spent on the open sea feeding on sea animals. Their bill is covered by several separated horny plates, their nostrils are elongated and tubular. Several of their smaller species search the seas for spots rich in planctonic shrimps using their sense of smell. The oil-like substance produced in their stomach is led to the bill by the tubular nostrils; they partially use this substance to make their plumage water-repellent. In case of emergency they spray smelly oil at their attacker through the nostril tubes and the bill. They lay only one egg, the breeding period is very long. The wingspan of the wandering albatross (Diomedea exulans) reaches 3 m. Wilson's storm-petrel (Oceanites oceanicus) breeds in the rock crevices of the shores of the Antarctic and the nearby islands, it is estimated to be the commonest bird on the Earth.