The Gyrfalcon (Falco rusticolus) also known by the abbreviation gyr is an Arctic bird of prey and considered the world’s largest falcon species.
They breed in the circumpolar region on Arctic coasts and tundra, and the islands of Europe, northern North America, and Asia, with the exception of some isolated populations found in Central Asian highlands.
Although the Gyrfalcon also lives mainly in the same region some individuals will disperse widely in the winter when food is scarce or after the breeding season. This individual vagrancy can make these birds travel very long distances and they are sometimes seen at lower latitudes.
Gyrfalcons are a very polymorphic species, meaning its plumage coloration varies widely, from white with black speckling individuals to much darker gray with barring specimens. These color variations are called morphs, and there are 4 of them with "white", "silver", "brown", and "black" Gyrfalcons.
Their plumage color seems to be linked to the falcon sex, with females accounting for most of the "black" birds while males usually won't get any darker than a dark slate grey. But their geographic location also plays a role on their coloration, with gyrfalcons found in Greenland being white with some grey flecking on their back and wings.
While other subpopulations usually display darker morphs on varying degrees. Juvenile Gyrfalcons tend to be brownish in color and darker than adult birds.
These are very large falcons with thick and powerful bodies making them about the same size as the largest buzzards although they are slightly heavier. Females in particular average 3 to 4.5 pounds in weight, and are much larger than males and almost double their weight.
The gyrfalcon may reach 19 to 26 inches (48 - 65 cm) in length and a wingspan ranging from 43 to 63 inches (110 - 160 cm). They have broad and pointed wings, a relatively long tail, longer than that of the peregrine falcon. Because they live in quite a harsh and cold environment their legs are fully feathered.
Subspecies / Etymology / Taxonomy
There are no subspecies currently recognized. The Gyrfalcon was first described as Falco rusticolus by Carl Linnaeus the Swedish naturalist in 1758.
Diet / Feeding
Like other falcon species the Gyrfalcon feeds mainly on medium-sized to large bird but will also take some land mammals. While on the Arctic tundra their prefered prey is the ptarmigan coastal Gyrfalcons will kill and eat mostly waterfowl such as ducks, grouse, and geese, or seabirds like the seagull.
But numerous other birds species may be hunted occasionally. Mammal species preyed upon include hares, rabbits, ground squirrels, lemmings, voles, and marmots. They have on rare occasions also been observed feeding on fish.
They may kill their prey in any circumstance being it on the air, on the ground, or sometimes even from the water. When hunting the Gyrfalcon scans the surrounding environment while flying or by perching on a high spot.
After spotting the prey these Falcons will normally start the chase by flying fast and very low over the ground trying to surprise the prey.
But in the last moment it will fly up just to dive straight down onto the prey for the kill. Sometimes the prey may also be chased relentlessly in flight over a very long distance.
The pair occupies the nesting site early in the season as early as late winter, they perform display actions including bowing and scraping behaviors. The Gyrfalcon doesn't build their own nest, they might simply use open ledges on a cliff with a natural or scraped depression with no nest present.
These Falcons will also use old nests abandoned by other bird species, such as the Golden Eagle (Aquila chrysaetos) or Ravens (Corvus corax) and occasionally even man-made structures.
They nest mostly on cliffs but in some areas of their range tree nesting is also frequent, using mostly abandoned raven's nests. The Gyrfalcon doesn't add material to existing nests when using them.
The females lay a clutch of up to 5 eggs, but usually 3 or 4 are laid near the end of April. The white or creamy white eggs display some reddish-brown spotting. Although the eggs are incubated by both parents, females do most of the incubation until they hatch approximately 35 days later.
For the first 2 or 3 weeks the young falcons are brooded mostly by females while males do most of the necessary hunting during this period spending countless hours hunting. After this initial period females will also start to hunt.
When feeding the younglings, adults will rip off small pieces of meat from the prey and give them to the chicks. As the young falcons grows, they start receiving bigger pieces of meat, and eventually the whole prey to practice the feeding behavior.
Adult Gyrfalcons will also defend their hatchlings vigorously against predators such as ravens, by flying after intruders, calling loudly and stooping forward try to scare it away, normally it works.
The young Gyrfalcons first fly at about 45 to 50 days of age and will leave the nest to hunt on their own 6 to 9 weeks after hatching. When learning to fly the young falcons might fall prey to land predators such as Arctic foxes if they land on the ground.
In these falcons both males and females reach sexual maturity and begin to reproduce when they are 2 or 3 years old.
Conservation status and major threats
In 2016 the Gyrfalcon was listed as a species of least concern on the IUCN’s Red List of Threatened Species. This classification is mainly due to their extremely large range and a global population estimated at about 70.000 individuals.
In the last 4 decades these Falcons have significantly increased (311%) their population in North America. But the overall population trend is likely to be stable due to declines in other pars of their range
The main threats to Gyrfalcon include the collection of eggs and young birds from the wild for the falconry black market, illegal shooting, and nest disturbance due to tourism has also become a problem.
The intensive hunting of their usual prey such as grouse, Ptarmigan and Willow Grouse may affect the species numbers. Climate change is considered the most significant threat since it's transforming many landscapes within the Gyrfalcon range.
The gyrfalcon is occasionally hunted by the Inuit for food and their feathers, which are used both in clothing and also religious rituals.
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Species: F. rusticolus