About Grus grus (Linnaeus, 1758)
The common crane (Grus grus) is a large, stately bird classified as a medium-sized crane. It measures 100–130 cm (39–51 in) in total length, has a wingspan of 180–240 cm (71–94 in), and ranges in body weight from 3 to 6.1 kg (6.6 to 13.4 lb). The nominate subspecies averages around 5.4 kg (12 lb), while the eastern subspecies G. g. lilfordi averages 4.6 kg (10 lb). Standard measurements for the species are: 50.7–60.8 cm (20.0–23.9 in) for the wing chord, 20.1–25.2 cm (7.9–9.9 in) for the tarsus, and 9.5–11.6 cm (3.7–4.6 in) for the exposed culmen. Males are slightly heavier and larger than females; weight shows the largest sexual size dimorphism in this species, followed by wing length, central toe length, and head length in both adults and juveniles. This species has an overall slate-grey plumage. Its forehead and lores are blackish, with a bare red crown and a white streak that runs from behind the eyes to the upper back. Its overall colour is darkest on the back and rump, and palest on the breast and wings. The primaries, tips of the secondaries, alula, tip of the tail, and edges of the upper tail coverts are all black, and the greater coverts droop into prominent explosive plumes. This combination of colour traits distinguishes the common crane from similar crane species found in Asia, such as the hooded crane (G. monacha) and black-necked crane (G. nigricollis). Juvenile common cranes have yellowish-brown tips on their body feathers, lack the adult’s drooping wing feathers and distinct bright neck pattern, and have a fully feathered crown. Every two years before migration, adult common cranes undergo a complete moult that leaves them flightless for six weeks, until new feathers finish growing. The common crane produces a loud, piercing trumpeting call that can be heard from a considerable distance, which it gives during flight and courtship display. It also performs a dancing courtship display that involves leaping with uplifted wings. The common crane breeds across Europe and through the Palearctic all the way to Siberia. The largest breeding populations by far are located in Russia, Finland, and Sweden. It is a rare breeder in southern and western Europe, with larger breeding populations in central and eastern parts of the continent. It has reappeared as a breeding bird in multiple western European countries where it was extirpated decades or centuries ago, including the United Kingdom, and since 2021, the Republic of Ireland. In Russia, the breeding range extends as far east as the Chukchi Peninsula. In Asia, the breeding range reaches as far south as northern China, Turkey, and the Caucasus region. This species is migratory. Common cranes that breed in Europe mostly winter in Portugal, Spain, and northern Africa. Autumn migration occurs between August and October at breeding areas, and from late October to early December at wintering sites. Spring migration begins in February at wintering sites and runs until early March, while at breeding areas it occurs from March through May. The migration phenology of common cranes is changing due to climate change. Hydraulic models, developed using data from crane censuses at spring migration stopover sites, can be used to estimate how many days unmarked cranes remain in a given area during spring migration. Important migration staging areas occur from Sweden, the Netherlands, and Germany through to China, with a large staging area around the Caspian Sea; many thousands of common cranes can be seen in a single day at these sites during autumn. Some birds winter in other parts of southern Europe, including Portugal and France. During mild winters, some individuals stay near their breeding locations year-round, even in northwestern Europe. Common cranes that breed in far eastern Europe, including European Russia, winter in the river valleys of Sudan, Ethiopia, Tunisia, and Eritrea, with smaller numbers wintering in Turkey, northern Israel, Iraq, and parts of Iran. The third major wintering region, used primarily by common cranes that breed in central Russia, is the northern half of the Indian subcontinent, including Pakistan. A small amount of wintering also occurs in Burma, Vietnam, and Thailand. Finally, the easternmost breeding common cranes winter in eastern China, where they are often the most common crane species. Migrating flocks of common cranes fly in a "V" formation. The species is a rare visitor to Japan and Korea, mostly individuals blown off course from the Chinese wintering population, and a rare vagrant to western North America, where individual birds are occasionally seen with flocks of migrating sandhill cranes. In Europe, the common crane mostly breeds in boreal forest, taiga, and mixed forest, at elevations from sea level up to 2,200 m (7,200 ft). In northern climates, it breeds on treeless moors, bogs, or dwarf heather habitats, usually in locations that also have small lakes or pools. In Sweden, breeding common cranes are usually found in small, swampy clearings within pine forests, while in Germany they use marshy wetlands. Breeding habitat in Russia is similar, though they will also nest in less typical habitats such as steppe and even semi-desert, as long as water is nearby. Most commonly, the largest number of breeding common cranes are found in wooded swamps, bogs, and wetlands, and the species appears to require quiet, undisturbed environments with minimal human interference. Even in areas where the species is common, breeding occurs at low density, typically between 1 and 5 pairs per 100 km2 (39 sq mi). In winter, this species moves to flooded areas, shallow sheltered bays, and swampy meadows. During the flightless moulting period, common cranes require shallow waters or dense tall reed cover for concealment. After the migration period, the birds regularly winter in open country, often on cultivated land, and sometimes in savanna-like areas; an example of this is wintering habitat on the Iberian Peninsula.
