The crane – short introduction
Apart from the most southeastern part of the continent only one crane species occurs in Europe, simplified referred to as crane. Because of the grey body colouring the species is scientifically referred in German to Graukranich (“grey” crane) or the Eurasian crane (Grus grus). The Eurasian crane reaches a standing height of 110 to 130 cm. The crane is thus considerably larger than the Grey Heron and the White Stork, birds for which it be mistaken. With a wing span of 220 to 245 cm it can compete for size with large eagles such as the White-tailed Eagle. During flight the crane can be identified by its long straight and thrust out neck. The very long legs clearly protrude the tail.
Mature birds have a black and white head- and neck marking and a red featherless head plate which noticeably stands out from the grey plumage. The head plate swells up bright red when the bird is aroused. The cranes most beautiful ornament is its tail veil. These drooping feathers cover the short tail and are prolonged inner secondaries as well as shoulder feathers of the wings, which can be erected when the bird is aroused or courting. The bird then seems even larger and more majestic.
The sexes are physically hardly distinguishable. However the male bird (cock) tends to be slightly taller and burlier than the female (hen) and reaches a weight of 5 to 7 kg whereas the female weighs around 5 to 6 kg. The over 10 cm long yellow coloured beak is wedge-shaped and slender.
Juvenile birds wear a cinnamon brown down plumage. Their completed youth dress is entirely brown apart from the sand coloured head. Only during the first winter does the black and white head marking gradually develop. However the youngsters need around 3 to 4 years to develop the complete colouring, read head plate and feather decorations like those of the mature birds.
The back feathering of the mature birds in particular can vary in colour from grey, grey brown to red brown. The brown colouring is individual and created by the cranes by application of ferrous mud on to the usually grey back feathers.
In captivity Eurasian cranes can reach an age of up to 40 years. Their life expectancy in the wild is much lower, though some ringed birds can reach an age of more than 25 years.
Cranes live in „life-long marriages“
Cranes become sexually mature at the age of three at the earliest, but usually begin breeding as from the age of four or older. The pairing probably takes place one or two years before the actual reproduction in non-breeding or summering groups. In the following period the engaged couple tries to occupy a breeding territory. It often then begins to build a nest. It is assumed that the crane couple normally stays together until one partner dies. However exceptions occur.
Cranes belong to the order of the Gruiformes in the classification of birds and to the family of cranes, besides the following families belong: limpkins, trumpeters, finfoots and rails. The cranes in turn are divided into four classes whereby the Common crane is assigned to the class Grus.
Two subspecies of the Common crane exist. The subspecies grus breeds in Northern Eurasia whereas the only recently described subspecies archibaldi occurs in eastern Turkey and in the Caucasus. After new genetic studies the lilfordi cranes of eastern Russia and Asia, previously described as an own subspecies, are now associated with the subspecies grus.
Diet – varied menu
Cranes are omnivorous animals. Their varied menu extends from small mammals, reptiles, small fish, frogs, snails, worms, insects and their larvae to corn and other grains, sunflower seed, peas and beans, peanuts, olives, berries, acorns, vegetables, potatoes and various plant parts.
The minor specialization is favourable for a migratory bird like the crane in order to adapt to the completely different conditions in the breeding-, resting- and overwintering areas.
Nevertheless obvious food preferences exist in particular times of the year. While foraging often happens in the forest, in bordering grassland as well as in peatlands and wetlands during breeding season, the cranes often selectively fly on to harvested farmland in the winter in order to search for harvest residues. In late summer/autumn these will usually be cereal stubble fields to begin with, while later on maize stubble fields are clearly preferred.
In the wintering areas in France and Spain harvested rice fields will be visited in specific regions. The Dehesas in the Spanish Extremadura and in Andalusia are also frequented in order to feed on the fallen holm- and cork oak acorns. In the winter half year the daily food requirements of a crane amounts to about 200-300 gr of grain.