Head to head
Snowy Owl vs Great Grey Owl
The snowy owl and the great grey owl are both huge northern owls that people put near the top of any "biggest owl" list, but they hold different records and live in different worlds. One is a bird of treeless tundra, built solid and heavy; the other is a bird of dense boreal forest, built long but astonishingly light.
| Snowy Owl | Great Grey Owl | |
|---|---|---|
| Scientific name | Bubo scandiacus | Strix nebulosa |
| Habitat | Open Arctic tundra; winters on open ground farther south | Dense boreal and montane forest |
| Plumage | White, barred with dark; old males nearly pure white | Grey, finely patterned, with a huge facial disc |
| Weight | About 1.6 to 2.9 kg (heaviest owl in North America) | About 0.7 to 1.7 kg despite its great length |
| Size record | Heaviest, and the bulkiest owl of the north | Tallest and longest owl, largest wingspan |
| When it hunts | Often by day, especially in the Arctic summer | Dusk, night, and early morning |
| Main prey | Lemmings and voles; also birds and rabbits | Voles and pocket gophers, located by sound |
| Conservation status | Vulnerable | Least Concern |
Snowy Owl vs Great Grey Owl: common questions
Which is the bigger owl, the snowy or the great grey?
It depends on how you measure. The great grey owl wins on length, standing up to about 84 cm from crown to tail tip, and on wingspan, up to around 1.5 m, making it the largest owl in the world by those measures. But the snowy owl wins decisively on weight, at up to nearly 3 kg against the great grey's usual 1 to 1.5 kg. The great grey looks enormous because it is wrapped in exceptionally deep, loose feathering that traps warmth in the boreal winter, but under that coat is a fairly ordinary owl body. So the great grey is the longest owl and the snowy is the heaviest; the true weight heavyweights among owls are the big eagle owls and the Eurasian eagle owl.
How does a great grey owl catch prey it cannot see?
By hearing alone. Its enormous facial disc works like a parabolic dish, funnelling faint sounds to ears that are set at slightly different heights on the skull, which lets the owl pinpoint a source in both direction and distance. Sitting on a low perch, it can hear a vole or pocket gopher tunnelling beneath the snow from many metres away. It then flies over, hovers briefly to fix the location, and drives its feet and face down through the snow, sometimes crashing through a hard crust that would take a person's weight, to grab the rodent it never saw. This snow-plunging is a signature behaviour of the species.
Why do snowy owls sometimes appear far south of the Arctic?
These movements are called irruptions, and they are tied to food. On the tundra, snowy owls feed heavily on lemmings, whose numbers swing through boom-and-bust cycles. In a good lemming summer the owls raise large broods, and when winter comes that big new generation of young owls spreads out to find hunting grounds, with many travelling well south into southern Canada and the northern United States, and occasionally much farther. It is mostly young birds that show up, often on airports, shorelines, and farmland that resemble open tundra. A big irruption year is usually the sign of a successful breeding season, not of starving birds fleeing a hard Arctic winter.