The increasing crane
With British numbers at an all-time high, David Callahan explores the complex life of one of our scarcest but most dramatic breeding birds: Common Crane.
With British numbers at an all-time high, David Callahan explores the complex life of one of our scarcest but most dramatic breeding birds: Common Crane.
Through heavy mist, dark, slowly flying shapes almost as big as humans are moving in flocks, shrieking as they go. They land, thousands of them en masse, crowding onto acres of waterlogged fields to feed on spilt crops and to display as late winter begins to warm.
These are Common Cranes wintering in the Hula Valley, Israel. However, Britain hosts its own microcosm of this awe-inspiring scene all year round, being one of only two countries (along with Turkey) in which the species is largely sedentary. While a regular vagrant in the intervening period – with a notable influx of more than 500 during October 1963 – cranes returned to breed in Britain in September 1979, when three birds took up residence at Hickling Broad, Norfolk, successfully nesting there in 1981. It was the first breeding effort for 400 years.
The Norfolk Broads remain Common Crane’s UK stronghold, but a combination of a reintroduction programme and the gradual increase of wild-bred birds has seen the British population reach a record high of more than 200 birds in East Anglia in 2020 – with 64 breeding pairs fledging 23 chicks centred on east Norfolk and the Fens – and up to five in Aberdeenshire. Unfortunately, though, the three Yorkshire pairs produced no chicks last season. More than half of all Common Cranes fledged in Britain since 1980 have been in the last five years. European breeding numbers approach 70,000 pairs, with half a million worldwide.
Historical finds
Common Crane was widespread in Britain until the 1600s, when it was wiped out by overhunting. It featured regularly in medieval feasts and is mentioned in Geoffrey Chaucer’s Parliament of Fowls (1382); the last
recorded birds were killed for a Norfolk banquet in 1650. Confusion over the extent of its medieval status arises from the general use of the word ‘crane’ to describe Grey Heron; place names such as Cranbrook and Cranfield may indicate the historical presence of either, but it’s hard to know which. Even so, Common Crane has been part of the British avifauna since the Eemian Interglacial (130,000-115,000 years ago).
A fossil crane found in Ilford, Essex, dates from this period and was significantly larger than its modern equivalent. It was originally given the name Grus primigenia, but overlaps Common Crane G grus in size and may have been a big male Common Crane, as males average larger than females. Cranes have been an important human cultural contributor since the Neolithic period (12,000-4,500 BC), with wingbones being fashioned into costumes and birds painted on walls at Çatalhöyük, Turkey, at around 7,000 BC.
The species is considered to be monotypic (having no subspecies) or to have two very similar forms: nominate, breeding across Eurasia and wintering in north-west Africa, the Nile Valley as far south as Ethiopia, the Near East, northern India and China; and ‘Caucasian Common Crane’ G g archibaldi, which has no red on its head and is resident around the Black Sea in a Critically Endangered population of about 200 individuals. A third subspecies, G g lilfordi, is sometimes recognised from Central Asia, but has minimal differences.
Adult Common Cranes are tall, long legged, long necked and bluegrey overall. They have charcoal-grey legs and black-and-white necks, with bustles of tertial plumes at their rear ends, similar to those of an ostrich.
Both males and females have a small red patch to the rear of their crowns. In summer, breeding pairs can become more russet brown on their backs, a colour derived from the mud of their breeding sites. Sexes are very similar, but males are larger with heavier beaks used as weapons in territorial disputes and against predators. Juveniles have no bustle, are pale grey all over and have an orange-brown head.
In flight, the black primaries and secondaries become apparent, and a small white ‘landing light’ can be seen at the base of the outer primaries. Flight is slow, with laborious beats on flattened wings and birds have been known to soar at up to 10,000 m. Travelling birds form loose single-file lines or V-shaped flocks, sometimes involving up to 400 individuals (fewer in Britain, of course).
Strictly crane dancing
As befits such a huge, gregarious waterbird, Common Crane’s display is ostentatious and loud. Two birds harshly trumpet, heads tilted back vertically, sending columns of steam into the air on colder days, as they erect the arched plumes of their bustles. They bow their heads, with 2-m wingspans spread and stiffly flapping, as each bird
leaps into the air while nodding its head. This partnered dance is repeated annually between monogamous pairs and appears to be both a bonding and mating ritual. Its drama was celebrated in the Russian ballet Song of the Cranes, which inspired Rudolf Nureyev to start his illustrious career. First-year birds dance more frequently than adults, practising an essential grown-up skill. Common Crane breeds in a variety of shallow wetland habitats, including meadows, bogs, reedbeds and forested swamps; the deciding factor seems to be a nesting area inaccessible to ground predators and humans. The European population mostly breeds between the northern tundra and steppe zones. Britain could support a lot more breeding cranes, though land drainage and intensive agriculture provide limits. The 6,475 sq km of peat-rich Flow Country in northern Scotland inexplicably fail to attract cranes despite the similarity to Eurasian breeding sites.
The nest territory varies in size from 2-500 ha, with a mound structure being built from reeds close to shallow freshwater. Nests can be almost one metre across and are usually used for the duration of a pair’s breeding life. Each is normally at least 230 m away from other crane nests.
About two eggs are laid and incubated for 30 days by the female. Chicks are able to run within 24 hours and are camouflaged with brown down. Parents will defend the nest from predators including Red Fox, Wild Boar, Western Marsh Harrier and White-tailed and Golden Eagles by jumping up and attacking with their beaks and feet, but will also feign a broken wing when approached by humans or large mammals. Corvids and Stoats are able to snatch eggs, while flooding may destroy the nest. Cainism – where the larger chick eats the smaller – has been observed, and this also affects nest productivity.
Protect and survive
Adult cranes become almost flightless in the month it takes the chicks to fledge, as they simultaneously moult their primaries for up to six weeks – the chicks gain the use of their wings over a parallel period. Around 48% of chicks to survive to autumn, while some 18% are still with us the following spring. Birds take about three years to reach sexual maturity and life expectancy can reach 40 years.
Once fledged, the majority of the Eurasian population moves south for winter, forming huge flocks – 40,000 winter in the Hula Valley, for example. Common Crane mostly winters on grasslands, stubble fields and pastures where the discarded parts of human food crops such as maize, potato, beet, rice, wheat and other spilt grains are particularly attractive to eat – as are cranberries, from which the fruit gets its name. Crop damage can be a problem and is estimated to cost around €200,000 in Sweden alone – crop rotation near breeding sites can help mitigate this.
Acorns, bulbs, and a wide variety of invertebrates are also consumed, along with amphibians, reptiles, small mammals and birds. The species’ strong bill enables the excavation of tubers and rhizomes, and efficient stripping of seed heads. British cranes are managed for conservation by planting ‘sacrificial crops’ such as barley solely for their use. It feeds by day, then roosts communally on marshes, bogs and even drained commercial fishponds.
Northern populations can travel more than 4,800 km to their winter quarters, including up to 19 stopover days,
juveniles accompanying their parents in family groups within larger flocks. Satellite-tracking shows they rest and feed up for a day or so at sites between 100 and 800 km apart. There are four main Western Palearctic migration routes: the West European (to Spain, France and north-west Africa), BalticHungarian-Adriatic, East European and Volga-Caucasian (all ending in the Nile Valley or Near East). The more southerly populations tend to be sedentary or short-distance migrants. Cranes begin to return north during February and March, a date that has advanced by 2-4 weeks over the last 40 years due to climate change. Wintering locations have shifted northwards, with an increase in France from 100 birds in 1980-81 to 68,000 at the turn of this century. Non-breeding cranes pass through Britain between March and June, with a return peak in late October.
Cranes of the world
In Libya, more than 1,000 birds winter on irrigated desert and roost on surrounding sand, but most wintering cranes feed in fields and roost in the shallow waters of nearby marshes. Spain hosts around 200,000 birds every winter, while up to 100,000 stage at Hortobágy NP, Hungary. Their sociability doesn’t stop individuals from stealing food from their neighbours or encroaching on personal space and there is much squabbling. Spanish peak winter numbers used to match acorn production in December but now correlate with the availability of rice stubble in January and February. Continental winter numbers have increased with greater restrictions on wildfowl hunting, and despite the fragmentation and degradation of potential habitats along their migration routes and in their winter quarters, which results in larger numbers being concentrated into smaller areas. Other dangers include urbanisation, pesticide poisoning (more than 50 cranes died simultaneously from a contaminated grain spillage in Germany in 2004) and collision with power lines and wind turbines. In Spain, cranes were killed by power lines 714 times more often than Great Bustards during the four winter months they were present. These collisions are the biggest source of premature adult mortality and probably occur because of a forward-looking ‘blind spot’ in flying cranes. The current small numbers present in Britain mean that this has happened on few occasions so far but could increase.
Common Crane’s world conservation status is considered as ‘Least Concern’ by BirdLife International due to its substantial global population. In Britain, its naturally occurring numbers are boosted by The Great Crane Project, which began reintroducing captive-fledged birds in 2010 (see box, page 40), though there is little sign of the wild and reintroduced groups joining up.
The best way to see cranes in Britain is to visit one of their strongholds (see box, left): either an approved site where they breed or in autumn and winter when they assemble on certain fields and marshes, often mingling picturesquely with wild swans and geese or flying to roost at dusk. We’re lucky that Common Crane now provides excitement at all times of the year in Britain, and can only hope this natural and historic component of our ancient megafauna will stay and multiply over the coming years. ■
Acknowledgements
Thanks to the RSPB’s Damon Bridge and Hywel Maggs for up-to-date information.