Gyrfalcon

Name and taxonomy

Carl Linnaeus described the gyrfalcon in 1758 as Falco rusticolus. Falco is late Latin for a falcon and comes from falx, a sickle. The word points at the curved talons. The epithet rusticolus means a dweller in the country. The English name arrived through French gerfaucon and medieval Latin gyrofalco. Falconers call the male a gyrkin.

The first part of the name has two possible sources. It may come from an Old High German word for a vulture, which points at the bird's size. It may instead come from the Latin word for a circle, after the way the bird circles for prey. Writers have named several subspecies, but none of them hold up. No living subspecies is accepted today. The Icelandic population is the most distinct of them.

Evolution and relatives

The gyrfalcon belongs to the hierofalcon group, which also holds the saker falcon. The group spread through the Holarctic near the start of the Late Pleistocene. Crossing between the species makes the DNA hard to read. A 2023 study suggested that gyrfalcons descend from eastern saker falcons. The same work found no support for the old idea that the Altai falcon is a gyrfalcon cross.

A fossil form named Falco rusticolus swarthi lived in the Late Pleistocene. Its bones turned up in Wyoming, New Mexico and California. The bird was larger than a modern gyrfalcon and lived in a dry temperate climate. It probably hunted land birds and mammals rather than seabirds. Plumage colour is tied to the melanocortin 1 receptor gene. One captive pair produced four young of four different colours.

Appearance

The gyrfalcon is broad-winged, long-tailed and heavier than a peregrine. The wings are pointed, which separates it from a buzzard at a distance. When it perches, the wingtips reach only two thirds of the way down the tail. An adult has yellow legs, eye-rings and cere, and a young bird has blue ones. The eyes look black, as they do in every falcon.

Four main morphs carry names: white, silver, brown and black. White birds are the only mostly white falcons in the world. Greenland holds the palest birds and Eurasia the darkest. Icelandic birds are pale, and no white birds occur in Eurasia. Black plumage appears to be linked to sex and shows mostly in females. Young birds are darker and browner than adults.

Females are much larger than males. A female measures 51 to 65 centimetres and weighs 1,180 to 2,100 grams. A male measures 48 to 61 cm and weighs 805 to 1,350 g. One female from eastern Siberia weighed 2,600 g. The wing chord runs 34.5 to 41 cm and the tail 19.5 to 29 cm.

Habitat and range

The gyrfalcon breeds on Arctic coasts, tundra and northern islands. It nests on cliffs and hunts over open ground with no cover. South of 60 degrees north it becomes a rare bird. In eastern Canada it breeds south to 55 degrees along the sea coast. It keeps out of the closed boreal forest.

In 2011 researchers showed that the bird spends much of the winter out on sea ice, well away from any coast. Most adults stay near the breeding grounds all year. Young birds and some northern breeders move south for the winter. A few reach the northern United States and perch low on fence posts over open fields. GBIF holds occurrence records from 33 countries. iNaturalist carries only 1,211 observations of the species.

Diet and hunting

The gyrfalcon eats birds and mammals and almost nothing else. It takes mammals more often than most other falcons. Rock ptarmigan and willow grouse are the chief prey on the tundra. On the coast it takes auks, gulls and sea ducks. On wetlands it takes waders and ducks such as the mallard. Prey ranges from a redpoll of about 20 grams to a goose of 4 kilograms.

Arctic ground squirrels and Arctic hares are the main mammal prey. The falcon takes Norway lemmings in the years when they swarm. It usually carries young hares, because a grown hare is too heavy to lift. Even so, a falcon can kill a hare of 4.5 kg and carry the pieces to the nest. Mice, water voles, muskrats, stoats, mink and Arctic fox pups also appear in the diet. Brown trout have been recorded, which is very unusual for this bird.

The hunt is a level chase rather than a dive. The falcon flies low over open ground and drives the prey to earth. It knocks the animal down with a blow from the talons and then lands on it. It can hold a chase long enough to wear the prey out. During the nesting season it stores large kills between meals.

Behaviour and social life

The gyrfalcon lives alone outside the breeding season. It hunts, feeds and roosts by itself. A pair comes together for the nesting season and then separates. Males start to hold a nesting territory at about the end of January. Females reach the site at the beginning of March. The pair then bonds for about six weeks before the eggs are laid.

The birds use the same cliff ledge year after year. Piles of prey remains build up on the ledge. Guano turns the rock below the nest white. The falcon drives off animals that come near the nest. Observers have watched gyrfalcons dive at brown bears.

The species is less aggressive than the peregrine falcon. As the Arctic warms, peregrines have moved north into Greenland. Peregrines attack gyrfalcons and can drive them off a site. The gyrfalcon avoids a fight, so it loses ground despite its size.

Communication and senses

The gyrfalcon hunts by sight. Almost every Arctic animal is camouflaged, so the falcon must pick prey out of plain ground. It can probably see a ptarmigan against snow from a great distance. A notched bill lets the bird kill a struggling animal quickly. Long pointed wings likely give it control in strong Arctic wind.

The gyrfalcon probably does most of its signalling at the nest. A pair spends about six weeks together before the female lays. Like other falcons, the two call and display to each other through that time. A parent screams and dives at a raven, a fox or a person near the ledge. Plumage colour may also carry information between birds. In Greenland the white birds lay earlier and raise more young than dark ones.

Reproduction and life cycle

The gyrfalcon almost always nests on a cliff. It builds nothing of its own. It takes a bare ledge, or the old nest of a golden eagle or a common raven. A few pairs use an old raven nest in a tree. The female lays at the end of April. A clutch holds 2 to 4 eggs, and 1 to 5 have been recorded.

An egg measures about 58.46 by 45 millimetres and weighs about 62 grams. The female does most of the sitting, with some help from the male. Incubation lasts about 35 days. All the eggs hatch within a day and a half of each other. A chick weighs about 52 grams when it hatches. Thick down lets the chicks hold their own heat after about ten days.

The female then leaves the ledge to hunt with the male. The parents brood the young for 10 to 15 days. The chicks leave the nest at seven to eight weeks. They become independent of their parents at three to four months old. Brothers and sisters may stay together through the following winter. A bird that reaches adulthood can live up to 20 years.

Predators and threats

An adult gyrfalcon has almost no natural enemy. Golden eagles are the only predator that attacks one, and they do so rarely. Common ravens take eggs and small chicks. Arctic foxes, red foxes, wolverines, brown bears and great horned owls kill young birds. Most deaths fall on inexperienced or injured birds.

People cause most gyrfalcon deaths. Cars kill some, and poisoned carrion set out for scavengers kills others. Shooting takes more. Pesticides cut the population in the middle of the 20th century. The species was listed as Near Threatened until 1994. Falcons catch bird flu easily, and a vaccine protects them.

Population and conservation

The IUCN lists the gyrfalcon as Least Concern, because the range is so large. One estimate puts the world total under 50,000 birds. Many of those are young birds that have not yet bred. Numbers have stayed fairly steady over the long term. Habitat loss matters little, because few people live in the nesting country.

Better pollution controls in wealthy countries let the population recover. Canada does not list the bird as endangered or threatened. It breeds in Alaska but only visits the rest of the United States. Illegal capture for falconry remains the main worry. Peregrine falcons moving north are a newer pressure in Greenland.

Relationship with humans

The gyrfalcon has been a falconry bird for more than a thousand years. Scandinavians tamed gyrfalcons from the seventh century onwards. Large numbers appear in records of gifts to the caliphs of Baghdad in the late ninth century. The settlement of Iceland in the 870s seems to have raised the supply of white birds. An Egyptian sultan paid 1,000 dinars for a live gyrfalcon and 500 for a dead one.

In Europe the bird was reserved for kings and nobles. A man of lower rank was rarely seen with one on his fist. In 12th-century northeast Asia the Khitan nobility hunted swans with gyrfalcons. The Liao emperor taxed the Jurchen in gyrfalcons and let collectors take them by force. That demand helped start the rebellion that destroyed the Liao empire in 1125.

Collecting wild raptors is illegal in North America. Birds are still taken in parts of the Old World and sold on the black market. Inuit hunters take a few birds for food, feathers and ceremony. Birdwatchers travel a long way to see one, which brings money to northern communities.

In culture and myth

Iceland placed a white falcon on a blue shield as its coat of arms in 1903. The falcon stayed in the arms until 1919 and left Danish heraldry in 1948. King Christian X founded the Order of the Falcon in 1921. The white falcon still sits at the centre of that order's insignia. The gyrfalcon is the official bird of the Northwest Territories in Canada.

The white gyrfalcon is the mascot of the United States Air Force Academy. Falconers have called the white bird the bird of kings for centuries. Medieval European rules kept the gyrfalcon out of the hands of ordinary people. Records of gifts to Baghdad show the same value placed on the white bird. The peoples of the far north treat the falcon as spiritually important.