Gyrfalcon

The gyrfalcon (/ˈdʒɜːrˌfɔː(l)kən/ or /ˈdʒɜːrˌfælkən/) (Falco rusticolus) is a bird of prey and the largest member of the falcon family. It lives in cold places, mainly breeding along the Arctic coasts and tundra of North America and Siberia. While they usually stay in these areas, some gyrfalcons travel farther after the breeding season.

Gyrfalcons come in different colors, ranging from all-white to dark brown, and these color differences are known as morphs. Like other falcons, female gyrfalcons are much bigger than the males.

For many years, people have admired gyrfalcons for their hunting skills. They often catch ptarmigan and waterfowl while flying, but they also hunt fish and small mammals.

Taxonomy and etymology

The gyrfalcon was first described by a Swedish scientist named Carl Linnaeus in 1758. The name "Falco rusticolus" describes it as a countryside-dweller. Its common name may come from old words meaning either a large bird like a vulture or a bird that flies in circles while hunting.

Description

The gyrfalcon is the largest falcon in the world. Males are about 48 to 61 centimetres long and weigh between 805 to 1,350 grams, while females are larger, ranging from 51 to 65 centimetres and weighing from 1,180 to 2,100 grams. The gyrfalcon has different color patterns, including white, silver, brown, and black, and can vary from all-white to very dark. These birds are larger and have broader wings than the peregrine falcon.

Systematics and evolution

The gyrfalcon belongs to a group called the hierofalcon complex. Scientists have found that these birds often mix their genes, making it tricky to study their DNA. The gyrfalcons spread out during a cold period long ago, moving to places near the North Pole and adapting to different areas. They are closely related to sakers, another type of falcon, but recent studies show they may have evolved from eastern sakers.

Gyrfalcons come in different colors depending on where they live. Those in Greenland are usually lighter, while others can be darker. They travel far and mix with birds from other places, so their color differences blend together. Scientists think the color differences are linked to a special gene.

Swarth's gyrfalcon

A type of gyrfalcon called Swarth's gyrfalcon lived during the last ice age, between 125,000 to 13,000 years ago. Fossils found in places like Wyoming, New Mexico, and California showed these birds were slightly larger than today's gyrfalcons. They lived in warmer, dry areas and likely hunted landbirds and small mammals, unlike today's gyrfalcons that eat sea birds and landbirds.

Ecology

The gyrfalcon lives in cold places near the Arctic and can be found on the coasts, tundra, and islands of northern North America and Siberia. During winter, some gyrfalcons travel far out to sea ice away from land.

Gyrfalcons eat only birds and mammals. They hunt by chasing their prey horizontally rather than diving from a high spot. Their favorite foods include birds like ptarmigans, seabirds, and ducks, as well as small mammals such as Arctic ground squirrels and hares. They can catch prey ranging from tiny birds to large geese.

Climate change has brought warmer summers to the Arctic, allowing peregrine falcons to move northward into areas where gyrfalcons live. While gyrfalcons are larger and better suited to cold climates, they are less aggressive than peregrines, who can attack and compete with them. Despite this, gyrfalcons are still considered to be at Least Concern on the IUCN's Red List.

Breeding

The gyrfalcon usually nests on cliff faces. These birds do not build their own nests but often use a bare spot on a cliff or an old nest left by other birds, like golden eagles and common ravens. A typical nest may have 2 to 4 eggs, though sometimes there can be just 1 or up to 5. The eggs are about 58.46 mm by 45 mm and weigh around 62 g. It takes about 35 days for the eggs to hatch. The baby birds stay in the nest for around 10 to 15 days and leave the nest when they are 7 to 8 weeks old. By 3 to 4 months, young gyrfalcons can live on their own, though they might still stay close to their siblings through the winter.

Gyrfalcons face few natural threats. Golden eagles are one of the few animals that might try to attack them, but even they usually avoid these strong birds. Brown bears have been known to dive-bomb gyrfalcons near their nests. The biggest danger to gyrfalcons comes from humans, through hunting or accidents like car collisions. Those that survive to adulthood can live up to 20 years.

Because gyrfalcons live in many places around the world, they are not considered in danger. While pollution from pesticides once lowered their numbers, better environmental practices have helped their populations recover.

Interaction with humans

The gyrfalcon has been a special bird for humans, especially for hunting and in a sport called falconry. It is the official bird of Canada's Northwest Territories. In Iceland, a white gyrfalcon appears on the country's coat of arms, and it is also the mascot of the United States Air Force Academy.

People in Scandinavia began taming gyrfalcons around the seventh century. These birds were traded and valued by merchants. In China, hunting with gyrfalcons became popular among noble people. Because these birds were rare, rules were made to control their use.

Gyrfalcons can get very sick from a type of flu called avian influenza. Scientists tested a special vaccine on some gyrfalcons, and it helped protect them from a stronger form of the flu. This shows that vaccines can keep gyrfalcons safe.