The Gyrfalcon (Falco rusticolus) is the world's largest falcon and a true bird of the high mountains, breeding on the northernmost mountain cliffs of Scandinavia. It is a big, powerful bird with broad wings and a long tail, giving a silhouette closer to a Goshawk than a Peregrine — males measure 50–63 cm and females 53–63 cm, with a wingspan of 110–130 cm; females, at 1.4–2.1 kg, are 30–40 percent heavier than the 1.0–1.5 kg males, a reversed size difference typical of raptors. Three colour morphs occur: white (a Greenland form, very rare in Sweden), grey (the most common form here) and a dark brown northern form, with finely streaked or spotted underparts and a far less pronounced moustache mark than the Peregrine's bold "helmet".
Its calls are heard mainly around the breeding cliffs between April and July: a hard, repeated "kak-kak-kak-kak" warns off intruders near the nest, stronger and hoarser than the Peregrine's sharper "kja-kja", while a softer "ee-tjip-tjip" passes between partners during prey exchanges. The Gyrfalcon builds no nest of its own, instead taking over old raven or eagle nests on cliff ledges — some Swedish sites have been used for centuries — where the female lays 3–4 eggs, incubated for 34–36 days, with chicks fledging after about 50 days and staying with their parents for several more weeks to learn to hunt. It is an almost total ptarmigan specialist, chasing Willow and Rock Ptarmigan in fast, low horizontal flight rather than the Peregrine's vertical stoop. Sweden holds only around 50–75 breeding pairs, concentrated in the Norrbotten and Lapland mountains, making the species classified as strongly threatened nationally even though it remains secure worldwide.
Read about this species in Swedish →