The large body size ("see also" Bergmann's rule) and distribution of Steller's sea eagle suggests it is a glacial relict, meaning it evolved in a narrow subarctic zone of the northeasternmost Asian coasts, which shifted its latitude according to ice age cycles, and never occurred anywhere else. Nests are built on large rocky outcroppings or at the tops of large trees on the coast and alongside large rivers with mature trees. Habitat with large Erman's birches ("Betula ermanii") and floodplain forests of larches, alders, willows and poplar are preferred. Some eagles, especially those that nest in sea coast, may not migrate. The timing, duration, and extent of migration depends on ice conditions and food availability.