The gyrfalcon is the largest falcon in the world, and gyrfalcons live in the far north, in the Arctic, where they are top predators. Gyrfalcons are one of four falcon species that breed in Alaska. As of January 2011, researchers knew of 79 gyrfalcon nesting territories on the Yukon-Kuskokwim Delta in Alaska, in a region of 130,000 square kilometers.

Researchers use motion-activated cameras at gyrfalcon nests on Alaska's Seward Peninsula to see the prey that is brought back. Cameras at gyrfalcon nests on the Seward Peninsula showed that gyrfalcons rely heavily on ptarmigan but also change their diet when ptarmigan numbers drop. Alaska biologists also fly slowly past mapped nest cliffs by helicopter and check whether raptors are using them, without landing.

A gyrfalcon hunts by scanning from a high rock perch or while flying, and it uses keen eyesight to spot potential prey. It often hunts by flying fast and low over the ground, usually in a level chase rather than a steep dive, and it may chase its prey over long distances.

Gyrfalcons eat mostly other birds, and ptarmigan are the gyrfalcon's main food. A gyrfalcon also eats waterfowl and seabirds, and some small mammals, such as ground squirrels and hares.

Gyrfalcons come in white, gray, and dark forms, called morphs, and white gyrfalcons are found mainly in Greenland.

A female is bigger than a male. Audubon lists male gyrfalcons as 19.7 to 22.8 inches (50 to 58 centimeters) long. A grown female can weigh as much as about 2.1 kilograms (about 4.5 pounds).

Gyrfalcons in the wild live about 162 months (13.5 years) on average, per the Bird Banding Laboratory figure on Animal Diversity Web.

In winter some gyrfalcons move south, and some stay in their territories. In winter a few gyrfalcons come south to the northern edge of the United States. Scientists discovered as recently as 2011 that some gyrfalcons spend a lot of the winter out on the ocean, far from any land.

In European falconry, the gyrfalcon was reserved for kings and nobles. There is evidence of gyrfalcons being tamed in Scandinavia from the seventh century onwards. Falconry is one of the oldest sports, dating back some 4,000 years.

Between about one and five gyrfalcons are taken from nests in Alaska each year for falconry, in a highly regulated way, as of 2020.

Male gyrfalcons begin defending a nesting territory in mid-winter. Gyrfalcons often return to the same nest site year after year. A gyrfalcon does not build its own nest, and it nests on cliffs. Gyrfalcons that nest in the Arctic often start laying eggs while the temperature is still below freezing. A gyrfalcon usually lays three or four eggs, and the eggs take about five weeks to hatch.

Gyrfalcon chicks hatch at a weight of around 52 grams. For the first one to three weeks, the male does all or most of the hunting while the female broods the young. Young gyrfalcons begin short practice flights at about five weeks old and spend the next eight weeks or more honing their flying. At 3 to 4 months old, young gyrfalcons become independent of their parents.

Gyrfalcons cached and re-delivered at least 9.1 percent of the items they brought to nests in a west Greenland study. At gyrfalcon nests in west Greenland, food deliveries peaked in the morning and evening.

Words to know

• ptarmigan: a bird
• raptors: birds of prey
• morphs: color forms
• cached: stored away