In Yakutia, gyrfalcon nests in tundra, forest-tundra, and taiga and may occur in the northeastern and, sometimes, in the northwestern parts, being almost absent or occasional over the large area separating these regions. The southern boundary of the nesting site is nowhere below 64 degrees N. In central Yakutia, gyrfalcon was suggested to be met as a visitant or migratory species. The long-term studies showed that this species occurred there in all the seasons, including winter periods. This fact became a reason to consider the bird as a migratory and wintering (not always) species, despite its repeated comings to inhabited localities that indicated difficulties in birds during winter periods. There are about 30 and 6 species of birds and mammals, respectively, in the gyrfalcon diet in Yakutia. The prevalence of birds is evident (65.4 to 91.3%). In the composition of food species, the share of willow and rock ptamigans is high everywhere, although in the Lower Kolyma tundra, they give way to ducks (19.2 and 30.7%, respectively). Ptamigans as an diet item seems to be of particular importance for the survival of the species. Gyrfalcons prey birds of medium size, such as ptamigans, ducks, and sandpipers. Large (geese. caterpillars) and small (small passerines) birds become gyrfalcon's prey less often. Species of open and semi-open habitats are mostly preferable among mammals. Drastic changes in the forage reserves of gyrfalcon are one of the most serious causes leading to the changes in its number and participation in the reproductive cycles.