Members of the genus falco are mostly medium-sized falcons, but vary from the large peregrine falcon to the small American kestrel. The wings are long and pointed and used almost continuously during flight. The bill is short, powerful, and with a distinct ‘tooth’ on each side. Most falcons of this group have a black teardrop-shaped ‘mustache’ mark on each side of the head. Falcons are fastflying birds of open country and are famous for attaining high speeds as they dive from high altitudes to knock birds out of the air.
Listen to the sound of Gyrfalcon
Copyright remark: Most sounds derived from xeno-canto
|wingspan min.:||109||cm||wingspan max.:||134||cm|
|size min.:||53||cm||size max.:||63||cm|
|incubation min.:||33||days||incubation max.:||35||days|
|fledging min.:||49||days||fledging max.:||35||days|
The most important habitat requirement is a safe nest site on a shelf of an abrupt cliff, providing shelter from mammalian predators and bad weather. Unless based on seabird colonies near-by, Gyrfalcons normally hunt over wide area of open terrain with short, sparse vegetation or willows and other shrub, or around large bodies of water. Birds dispersing elsewhere for winnter seek similar open conditions with abundant prey on moors, steppes, coastal belts, around open lakes and reservoirs, even farmland or sometimes towns.
already in April, and the nest site has to provide also shelter from wind, rain (snow cover) and extreme exposure of sunlight by a well-developed overhang. If Gyrfalcons are short of suitable cliffs they sometimes breed in stick nests in trees, more commonly in arctic Russia and Siberia than in north-western Europe. Usually a pair has 2-5 alternate nest sites within a few kilometres, but sometimes up to ca. 15 km from each other.
The normal clutch size is 3-4 eggs, and they are incubated for 34-36 days mostly by the female. The young are brooded up to the age of 10-32 days. Fledging period is 45-50 days, and after that the young are dependent on their parents for several weeks. The young disperse from the natal territory 3-4 weeks after fledging, but some stay there for up to 5-11 weeks.
In most populations the mean productivity is 1.5-2 fledglings per breeding attempt or 2-3 fledglings per successful pair. Generally the brood size varies less than the number of successful pairs; the latter varies usually from 30 to 80% and is dependent on weather conditions during the early phase of nesting and the abundance of food. Although there may be plenty of food, heavy snowstorms or low temperature lasting for days during March and early April may prevent the female from reaching the required condition for egg laying. Some territories are occupied more or less annually, and produce a high number of young compared with territories occupied irregularly. Most birds probably start breeding at 2-3 years old. The youngest individuals of a population have a higher possibility to raise young successfully in years with abundant food supply than in years with poor food availability.
Breeding Gyrfalcons may hunt in an area of at least 300-600 km2, thus ranging some dozens of kilometres from their nest. They probably concentrate, however, in the most productive parts of the home range. The proportion of other prey than grouse (waterfowl, waders, larids and other mediumsized birds) is higher, on average, for pairs nesting near coast, lake, wetland or peatland areas than in homogenous heathland habitats.
The Gyrfalcon is distributed circumpolarly over a large part of the tundra zone and at the northern limit of the coniferous forest zone, including arctic-alpine mountainous heath, birches and willow scrub. In Europe it breeds in Greenland, Iceland, Norway, north-western Sweden, northern Finland, northern half of the Kola Peninsula and along the timberline east of the Kanin peninsula. Within European Union the species breeds only in northern Finland and Sweden. The majority of the adult
population probably stays in the breeding area, except for high Arctic, throughout the year, but at least part of the immature and some adult birds winter in coastal areas of the Atlantic or Arctic Ocean.
The population is fairly well known in Fennoscandia and Iceland but poorly so in Greenland and especially Russia. The total European population has been estimated recently at ca. 800-1,300 without Greenland, and 1,300-2,300 if Greenland is included. According to the most recent information compiled for this report, there are 1,650-2,650 territorial pairs in the whole of Europe. Earlier estimates do not deviate markedly from this, except for Russia. Gyrfalcon populations fluctuate considerably both annually and in longer terms, depending on the abundance of Willow Grouse and Ptarmigan. The total population in Europe has probably remained at the same general level since the mid-1900s, although numbers appear to have declined at least locally in northern Fennoscandia and north-western Russia also during the 20th century.
Continental populations mainly resident and dispersive; probably partially migratory in Russia where regular movement from tundra to taiga. Overwinter as far north as Lapland, Murmansk, and Kanin Peninsula, though others (especially juveniles) wander south and west in autumn.
Falco rusticolus, in Eastern North America