Gyrfalcon (Falco rusticolus)

Gyrfalcon (Photo: Seabamirum )

Barents sea region red-listed species
Typography
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The Gyrfalcon is the largest and the most Arctic falcon in the world. It is heavy and powerful, more bulky than the closely related Peregrine (Falco peregrines). The Gyrfalcon is 53–63 cm long with a wingspan of 110–130 cm. The Gyrfalcon weighs 800–2,100 gr., female being considerably heavier than male. Otherwise the sexes are similar, and the juvenile is more streaked than the adult. The Gyrfalcon is monotypic but there are three colour forms in the

circumpolar range, with the white form living in maritime parts of the range, and the grey and dark forms in continental areas. The Gyrfalcons breeding in Barents region are grey on back with paler barring and have whitish undersides with darker streaks and spots.

Distribution/range – global and regional

In Barents region the Gyrfalcon breeds in Arctic, Subarctic and alpine areas in Norway, northwestern Sweden, northern Finland, and northern Russia. In the south, the range extends to the northern margins of the boreal coniferous forest zone (Cade et al. 1998, Potapov & Sale 2005, Watson et al. 2011). The range covers almost the whole of Norway, western and northern Sweden, northern Lapland and the tundra zone both west and east of the White Sea. In other parts of the world the species is distributed throughout the tundra and forest-tundra zones in Greenland, Iceland, Siberia, Alaska and Arctic Canada. The majority of adults are resident except in the high Arctic, from where they fly southwards and winter usually on the coast or ice-covered seas, like also the juveniles in most populations (Watson et al. 2011). The falcons remain, however, within the breeding range in winter, too.

Key habitats - seasonality

The Gyrfalcon breeds in tundra and forest-tundra at or above the northern tree line, and in the respective alpine zones, including the Arctic and Subarctic coasts (Cade et al.1998, Potapov & Sale 2005, Watson et al. 2011). The species breeds also in broken pine or birch forests along river valleys and in mountain slopes further south from the tree line, especially In Fenno-Scandia and Russia. The most important habitat requirement is a safe nest site on a shelf of an abrupt cliff as well as sufficient avian prey populations in the neighbourhood. Except seabird colonies on the coast, Gyrfalcons normally hunt mostly ptarmigans (Lagopus spp.) over open terrain with short and sparse vegetation. Birds dispersing outside their natal or breeding territories for winter seek similar open environments in tundra, coastal belts, around open lakes and sometimes even in farmland.

Biology – migration, life strategy, feeding, trophic relation, etc.

The Willow Ptarmigan (Lagopus lagopus) and the Rock Ptarmigan (Lagopus muta) are the main prey of the Gyrfalcon all over the world and throughout the year (Cade et al. 1998, Koskimies & Sulkava 2011, Nielsen 2011, Potapov 2011a). The two Ptarmigans form almost 100% of the diet from late autumn to spring and 80–90% during breeding in most inland regions. The falcons hunt waders, larids, waterfowl, and even passerines in varying degrees during the nestling period, and they are major food also in coastal territories and close by large lakes. The nesting territory with more or less common hunting grounds covers usually hundreds of square kilometres all over the range (Watson et al. 2011). In Finland, for example, the breeding density is 1.7–2.7 pairs/1000 km2 at most (Koskimies 2011). The proportion of nesting pairs of all occupied territories in a Gyrfalcon population varies considerably both spatially and temporarily, depending on the availability of food In Finnish Lapland, for example, only 10% of occupied territories hold a nesting pair during the lowest Lagopus densities compared to 60–80% during high grouse populations (Koskimies 2011). Also the breeding success is dependent on the availability of prey although it fluctuates less from year to year than the percentage of pairs able to start nesting. The Gyrfalcon breeds on a cliff ledge, in lowlands also in a tree, usually in an old stick nest of the Raven (Corvus corax). The female starts laying in late March or early April. The normal clutch size is 3–4 eggs, the incubation lasts 34–36 days, and the normal fledging period is 45–50 days, after which the young are dependent on their parents for 1–2 months. Age of first breeding is 2–3 years. The site- and mate-fidelity is high (Koskimies 2011, Booms 2011).

Population status – numbers and trends

Potapov & Sale (2005) estimated the global population of the Gyrfalcon as ca. 8000–11 000 pairs, while BirdLife International (2012) suggested 110 000 individuals. The European breeding population of the Gyrfalcon was estimated from 1300 to 2300 pairs in the early 2000s by BirdLife International (2004), of which about two thirds breed in Greenland and Iceland. Recent annual population estimates in Barents region are as follows: Norway 370–650, Sweden 100–190, Finland 15–35, and Kola Peninsula 10–25 breeding pairs, respectively (Koskimies 2011, Heggøy & Øien 2014, Ulla Falkdalen et al. unpubl.). The populations breeding in northern Russia east of the White Sea are much poorer known; based on censuses from single study areas a rough estimate of 100–200 pairs has been published by BirdLife International (2004), while Koskimies (1999) and Potapov & Sale (2005) suggested markedly higher figures. The population in Barents region has remained at the same general level in recent decades, like in Iceland, Greenland and North America, but is considerably smaller than in the 19th century at least in Fenno-Scandia (Johansen & Østlyngen 2011, Koskimies 2011). Since 2008, however, the number of breeding pairs have remained at considerably lower level due to exceptionally long-lasting and extensive population low of the Willow Ptarmigan.

Threats – natural and anthropogenic

Both the EU Action Plan (Koskimies 1999) and the Finnish conservation assessment (Koskimies & Ollila 2009) considered two threats of the Gyrfalcon as highly important, and relevant in the whole of Barents region: reduced prey numbers, and disturbance of nest sites. In addition, over a longer time perspective, climate change is going to diminish a great part of the present breeding range (Huntley et al. 2007). The Gyrfalcon is totally dependent on the adult segment of the main prey populations, the Willow and Rock Ptarmigan, from autumn to early summer, and starts breeding during the annual low in the numbers of prey. The average density of the ptarmigan populations seems to be at considerably lower level nowadays than decades ago (e.g. Väisänen et al. 1998, Koskimies & Sulkava 2011), possibly due to excessive hunting, lowering of the habitat quality e.g. due to overgrazing by reindeer, and due to increased predation pressure especially by the Red Fox (Vulpes vulpes, Koskimies 1999). The second threat of highest importance, disturbance of nesting birds, is caused by increasing number of people hiking, rock climbing, photographing nature, watching birds, or moving around Gyrfalcon nest-sites because of other outdoor activities. Threats of lower importance include habitat fragmentation, also for the ptarmigans, because of building of dams and reservoirs, roads, snow mobile routes, etc. Many clutches and broods are probably robbed every year for egg-collections and falconry, most intensively and regionally causing marked population declines in Russia, including Kola Peninsula (Koskimies & Kohanov 1998, Potapov 2011b). Other threats of low importance include illegal shooting and unintentional trapping of adult falcons for game protection and by grouse trappers, collision with reindeer fences and power lines, lack of twig nests due to decline of Raven populations, as well as chemical contamination (Cade et al. 1998, Koskimies 1999, 2011, Koskimies & Ollila 2009).

Conservation measures and needs

The Gyrfalcon is not included either in the global or the European IUCN Red List because of its large and stable range and global population (class: least concern (LC), BirdLife International 2013). In Barents region the Gyrfalcon is classified as follows: in Norway near threatened (NT), in Sweden vulnerable (VU), in Finland endangered (EN), and in Murmansk Region vulnerable (VU). A Species Action Plan by the European Union and for the whole European range was published in 1999 (Koskimies 1999). In Finland, a status assessment and conservation plan was published a decade later (Koskimies & Ollila 2009). Conservation measures of high importance include increasing food supply by habitat management and hunting quotas which favour ptarmigan species, taking Gyrfalcon territories into account when organizing recreational and other human activities which may cause disturbance to breeding, and keeping nest-sites secret and increasing guarding to stop robbing of eggs and young. Monitoring and research on viability of populations should be activated.