The Alpine chough /ˈtʃʌf/, or yellow-billed chough, (Pyrrhocorax graculus) is a bird in the crow family, one of only two species in the genus Pyrrhocorax. Its two subspecies breed in high mountains from Spain eastwards through southern Europe and North Africa to Central Asia, Nepal, and it may nest at a higher altitude than any other bird. The eggs have adaptations to the thin atmosphere that improve oxygen take-up and reduce water loss.
This bird has glossy black plumage, a yellow beak, red legs, and distinctive calls. It has a buoyant acrobatic flight with widely spread flight feathers. The Alpine chough pairs for life and displays fidelity to its breeding site, which is usually a cave or crevice in a cliff face. It builds a lined stick nest and lays three to five brown-blotched whitish eggs. It feeds, usually in flocks, on short grazed grassland, taking mainly invertebrate prey in summer and fruit in winter; it will readily approach tourist sites to find supplementary food.
Although it is subject to predation and parasitism, and changes in agricultural practices have caused local population declines, this widespread and abundant species is not threatened globally. Climate change may present a long-term threat, by shifting the necessary Alpine habitat to higher altitudes.
The adult of the nominate subspecies of the Alpine chough has glossy black plumage, a short yellow bill, dark brown irises, and red legs. It is slightly smaller than red-billed chough, at 37–39 centimetres (14.6–15.3 in) length with a 12–14 cm (4.7–5.5 in) tail and a 75–85 cm (30–33 in) wingspan, but has a proportionally longer tail and shorter wings than its relative. It has a similar buoyant and easy flight. The sexes are identical in appearance although the male averages slightly larger than the female. The juvenile is duller than the adult with a dull yellow bill and brownish legs. The Alpine chough is unlikely to be confused with any other species; although the jackdaw and red-billed chough share its range, the jackdaw is smaller and has unglossed grey plumage, and the red-billed chough has a long red bill.
The subspecies P. g. digitatus averages slightly larger than the nominate form, weighing 191–244 grams (6.8–8.7 oz) against 188–252 g (6.7–9.0 oz) for P. g. graculus, and it has stronger feet. This is in accordance with Bergmann's rule, which predicts that the largest birds should be found higher elevations or in colder and more arid regions. The extremities of the body, the bill and tarsus, were longer in warmer areas, in line with Allen's rule. Temperature seemed to be the most important cause of body variation in the Alpine chough.
The flight of the Alpine chough is swift and acrobatic with loose deep wing beats. Its high manoeuvrability is accomplished by fanning the tail, folding its wings, and soaring in the updraughts at cliff faces. Even in flight, it can be distinguished from the red-billed chough by its less rectangular wings, and longer, less square-ended tail.
The rippling preep and whistled sweeeooo calls of the Alpine chough are quite different from the more typically crow-like chee-ow vocalisations of the jackdaw and the red-billed chough. It also has a rolling churr alarm call, and a variety of quiet warbles and squeaks given by resting or feeding birds. In a study of chough calls throughout the Palearctic region it was found that call frequencies in the Alpine chough showed an inverse relationship between body size and frequency, being higher-pitched in smaller-bodied populations.
The Alpine Chough breeds in mountains from Spain eastwards through southern Europe and the Alps across Central Asia and the Himalayas to western China. There are also populations in Morocco, Corsica and Crete. It is a non-migratory resident throughout its range, although Moroccan birds have established a small colony near Málaga in southern Spain, and wanderers have reached Czechoslovakia, Gibraltar, Hungary and Cyprus.
This is a high-altitude species normally breeding between 1,260–2,880 metres (4,130–9,450 ft) in Europe, 2,880–3,900 m (9,450–12,800 ft) in Morocco, and 3,500–5,000 m (11,500–16,400 ft) in the Himalayas. It has nested at 6,500 m (21,300 ft), higher than any other bird species, even surpassing the Red-billed chough which has a diet less well adapted to the highest altitudes. It has been observed following mountaineers ascending Mount Everest at an altitude of 8,200 m (26,900 ft). It usually nests in cavities and fissures on inaccessible rock faces, although locally it will use holes between rocks in fields, and forages in open habitats such as alpine meadows and scree slopes to the tree line or lower, and in winter will often congregate around human settlements, ski resorts, hotels and other tourist facilities. Its penchant for waiting by hotel windows for food is popular with tourists, but less so with hotel owners.
In the summer, the Alpine chough feeds mainly on invertebrates collected from pasture, such as beetles (Selatosomus aeneus and Otiorhynchus morio have been recorded from pellets), snails, grasshoppers, caterpillars and fly larvae. The diet in autumn, winter and early spring becomes mainly fruit, including berries such as the European Hackberry (Celtis australis) and Sea-buckthorn (Hippophae rhamnoides), rose hips, and domesticated crops such as apples, grapes and pears where available. It has been observed eating flowers of Crocus vernus albiflorus, including the pistils, perhaps as a source of carotenoids. The chough will readily supplement its winter diet with food provided by tourist activities in mountain regions, including ski resorts, refuse dumps and picnic areas. Where additional food is available, winter flocks are larger and contain a high proportion of immature birds. The young birds principally frequent the sites with the greatest food availability, such as refuse dumps. Both chough species will hide food in cracks and fissures, concealing the cache with a few pebbles.
This bird always forages in groups, which are larger in winter than summer, and have constant composition in each season. Where food resources are restricted, adults dominate young birds, and males outrank females. Foraging areas change altitudinally through the year, depending on climatic factors, food availability and food quality. During the breeding season, birds remain above the tree line, although they may use food provided by tourists at refuges and picnic areas.
Movement to lower levels begins after the first snowfalls, and feeding by day is mainly in or near valley bottoms when the snow cover deepens, although the birds return to the mountains to roost. In March and April the choughs frequent villages at valley tops or forage in snow-free patches prior to their return to the high meadows. Feeding trips may cover 20 km (12 mi) distance and 1,600 m (5,200 ft) in altitude. In the Alps, the development of skiing above 3,000 m (9,800 ft) has enabled more birds to remain at high levels in winter.
Where their ranges overlap, the two chough species may feed together in the summer, although there is only limited competition for food. An Italian study showed that the vegetable part of the winter diet for the red-billed chough was almost exclusively Gagea bulbs dug from the ground, whilst the Alpine chough took berries and hips. In June, red-billed choughs fed mainly on caterpillars whereas Alpine choughs ate crane fly pupae. Later in the summer, the Alpine chough consumed large numbers of grasshoppers, while the red-billed chough added cranefly pupae, fly larvae and beetles to its diet. In the eastern Himalayas in November, Alpine choughs occur mainly in juniper forests where they feed on juniper berries, differing ecologically from the red-billed choughs in the same region and at the same time of year, which feed by digging in the soil of terraced pastures of villages.