The Great Grey Owl rivals the Eurasian Eagle Owl and the Blakiston’s Fish Owl as the world’s largest owl.
They breed in North America from Lake Superior to the Pacific coast and Alaska, and from Scandinavia across northern Asia. They are permanent residents, but may move south and southeast when food is scarce.
These birds wait, listen and watch for prey, then swoop down; they also may fly low through open areas in search of prey. Their large facial disks focus sound, and the asymmetrical placement of their ears assists them in locating prey.
They have excellent hearing, and may capture prey moving beneath 60 cm (2 feet) of snow in a series of tunnels. These owls can crash through snow that could support the weight of a 180-pound person.
Great Grey Owls reply almost fully upon small rodents, with voles being their most important food source. Locally, alternative prey animals (usually comprising less than 20% of prey intake) include hares, moles, shrews, weasels, thrushes, grouse, Gray Jays, small hawks and ducks.