Tundra islands in the northern Lena delta are used as breeding habitat of the Black-bellied Brent Geese (Branta bernicla nigricans). This part of the Siberian tundra forms the westernmost area of the breeding range of this sub-species, where also the Dark-bellied Brent Geese (Branta bernicla bernicla), migrating in winter to the West, have been recorded.