Project SNOWstorm tags snowy owls with a backpack harness of low-friction ribbon that goes over the bird's wings. Older satellite tracking logged a single location a day at best, but the cellular tags used by Project SNOWstorm can store up to 100,000 locations. As of August 2024, the project was using, in 2024, satellite transmitters that weigh just 17 grams, instead of the 45-gram GPS/GSM units it normally uses. As of August 2024, it had put satellite transmitters on 10 young owls from six nests on Bylot Island. On Bylot Island, researchers also fitted females with satellite transmitters and tracked their movements in real time for up to 3 years.

Snowy owls nest on the tundra in the far north of the world, on open, treeless land. Tracking showed snowy owls to be among the great nomads of birds, ranging thousands of miles across the Arctic, and one tracked snowy owl moved 881 miles (1,418 km) across an area of 1,784 square miles (4,621 sq. km). Snowy owls do not show fidelity to a particular breeding site: they do not return to the same place each year, and a snowy owl breeding in central Canada one year may be in Greenland the next. Birdwatchers help count snowy owls by reporting sightings through eBird, and winter snowy owl numbers in the south probably relate to how much prey there is in the north.

Watching owls also shows when they hunt. Near Calgary, Canada, snowy owls that were watched spent 98% of the daylight hours perched and were alert more often than resting, while owls tracked by Project SNOWstorm around the Great Lakes hunted almost exclusively at night. Snowy owls hunt at any time of day, except in severe weather, and they often hunt in the daytime, sitting still on a high spot and watching for food. In a study of snowy owl hunting, owls used two main methods: perch and scan, and hover and scan.

A snowy owl's favorite food is the lemming, a small mouselike animal. On Bylot Island, collared and brown lemmings make up about 96% of a breeding snowy owl's diet, and a snowy owl may eat about 1,600 lemmings in a year. Each owl must catch the equivalent of 7 to 12 mice a day to meet its food needs. To raise young across most of their range, snowy owls need high numbers of lemmings, small rodents weighing 60 to 90 grams, and lemmings fuel the owls' reproduction. Snowy owls nest on the tundra mainly in years when lemmings are plentiful, and a snowy owl lays more eggs in years when there is plenty of prey.

Words to know

• harness: body strap
• transmitters: signal senders
• fidelity: faithful return