Crane

Cranes are tall wading birds that belong to the Gruidae family. There are 15 species of cranes (order Gruiformes). Cranes superficially resemble herons, but they are usually larger and hold a heavier bill, a partly naked head, an elevated hind toe, and more compact plumage. In-flight, the long neck is stretched out in front, and the stilt-like legs are trailing out behind.

Evolution of Cranes

Cranes are an ancient species, with the first fossils discovered in the Eocene deposits of North America. Living forms can be found across the world except in South America, but the populations of several are endangered by habitat destruction and hunting.

The representation of the Crowned crane (Balearica pavonina [regulorum]) is given below.

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These graceful terrestrial birds forage in plains and marshes, eating a variety of small animals as well as grass shoots and grain. Two olive-gray eggs, which are spotted with brown, are laid in weed stalks and a nest of grasses on the drier ground in a field or marsh. Year after year, a similar nest can be used. The brownish, downy young may run around shortly after hatching. The trachea (or windpipe) is short and simple in a newborn, but it grows longer with maturity, coiling around itself like a French horn. It lies as buried in the breastbone's hollow keel and reaches a length of 1.5 metres (5 ft) in the adult whooping crane (or Grus americana).

The representation of the Whooping crane (Grus americana) is given below.

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The sandhill crane (which is the G. Canadensis) breeds from Alaska to Hudson Bay; it was formerly bred in the regions of south-central Canada and the Great Lakes of the United States, but now, it is rare in these particular regions. This brownish-gray crane is around 90 to 110 cm (35 - 43 inches) long. Its call is harsh, long, and penetrating. The Florida sandhill crane (which is G. c. pratensis), nonmigratory, smaller race that breeds in southern Georgia and Florida. The other subspecies of sandhills are classified as either endangered or rare.

The common crane (which is G. grus) breeds in northern Asia and Europe, wintering in the large flocks in India, Northern Africa, and China. The native companion, Australian crane, or Brolga (which is G. rubicunda), lives in southern New Guinea and Australia. The demoiselle crane (which is Anthropoides Virgo) breeds in southeastern Europe, Algeria, and Central Asia; the crowned crane (Balearica pavonina [or the regulorum]), over nearly all of Africa; and the wattled crane (Bugeranus carunculatus), in Africa and Eastern southern.

Below is an illustration of sandhill cranes (Grus Canadensis).

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Description

Cranes are very large birds and are often considered the tallest flying birds in the world. They range in size from the demoiselle crane, which is 90 cm (35 inches) long, to the sarus crane, which may reach a length of 176 cm (69 inches), with the red-crowned crane being the largest crane bird at 12 kg (26 lb) before migrating. They have long necks and legs, as well as sleek bodies and broad, rounded wings. Males and females have similar outward appearances, however males are significantly larger than females.

The plumage of cranes differs by habitat. Species inhabiting vast open wetlands tend to contain more white in their plumage than do species, which inhabit forested habitats or smaller wetlands that tend to be more grey. Generally, these white species are also larger. The smaller size and the color of forest species are thought to help them in maintaining a less conspicuous profile while nesting; sandhill and common cranes, for example, coat their plumage with mud, which some observers believe helps them hide when nesting.

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The above figure shows the bare area of skin on the sandhill crane's face may change color or even expand in the area when the bird is excited.

Many species of cranes have a few areas of bare skin on their faces; the only two exceptions are the demoiselle and blue cranes. This skin can be used in communication with the other cranes and may be expanded by relaxing and contracting muscles and changing the color intensity. On the head, feathers can be moved and erected in the wattled, blue, and demoiselle cranes for signaling also.

In addition, important to communication is the length and position of the trachea. The trachea is shorter and only slightly impressed in the two crowned cranes upon the bone of the sternum, whereas the trachea of the other species is longer, and they penetrate the sternum. In a few species, the whole sternum can be fused to the bony plates of the trachea, and this helps to amplify the calls of cranes, allowing them to carry for many kilometres.

Distribution and Habitat

The cranes contain a cosmopolitan distribution, taking place across most of the world's continents. They are not found from Antarctica and, mysteriously, from South America. East Asia has the most crane species, with eight, followed by Africa, which has five resident species and a sixth that winters there. Europe, Australia, and North America contain two regularly taking place species each. The Balearica (with two species) and Leucogeranus (with one species) crane genera are both restricted to Africa and Asia, respectively. The other two genera, Grus (containing Bugeranus and Anthropoides) and Antigone, are both widespread.

Demoiselle cranes (which is the Grus Virgo) in Mongolia: Central Asian populations (asian crane) of this species migrate to Northern India in the winter season.

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Several species of cranes are dependent on grasslands and wetlands, and most species nest in the shallow wetlands. A few species lay their eggs in wetlands but migrate their chicks to uplands or grasslands to eat (returning to the wetlands at night), but others stay in wetlands throughout the breeding season. Even the demoiselle blue and crane, which can nest and feed in grasslands (or even deserts or arid grasslands), need wetlands for roosting at night.

The Sarus Crane in the south Asia region is unique in having a significant breeding population using the agricultural fields to breed in areas alongside very high density of humans and intensive farming, largely because of the positive attitudes of farmers towards the cranes. In Australia, the Brolga takes place in the breeding areas of the Sarus Cranes in Queensland state, and they also achieve sympatry by using various habitats. Sarus Cranes in the Queensland region largely live in the Eucalyptus-dominated riverine, while most of the Brolgas use non-wooded regional ecosystems, which include vast grassland habitats. The only two species, which do not always roost in wetlands, are given as the two African crowned cranes (Balearica), the only cranes to roost in trees.

A few crane species are sedentary, remaining in similar areas throughout the year, while the others are highly migratory, traveling thousands of kilometres every year from their breeding sites. Some species like Sarus Cranes contain both sedentary and migratory populations, and healthy sedentary populations contain a large proportion of cranes, which are not territorial, breeding pairs.

Behavior and Ecology

The cranes are the diurnal birds, which differ in their sociality by location and season. They are territorial, and they usually remain on their territory all the time during the breeding season. They also tend to be gregarious during the non-breeding season, forming big groups to interact, roost, and in a few species, forage. Sarus Crane breeding pairs maintain territories throughout the complete year in south Asia, and non-breeding birds live in flocks, which can also be seen throughout the year. Individual cranes are believed to be safer when flying and resting in big groups of cranes, and young unmated birds are more likely to meet partners.

Calls and Communication

Cranes are highly vocal and contain many specialized cells. After hatching, the vocabulary begins with low and purring cries for maintaining contact with their parents, as well as food-begging cries. "Flight intention" calls and warning calls are two more cries that can be employed as chicks and are both maintained throughout adulthood. Cranes are the most noticeable because of their booming duet calls, which can be used to identify specific pairs.

Feeding

The cranes consume a variety of food, both plant and animal matter. They eat leaves, seeds, nuts, and acorns, fruit, berries, worms, insects, small reptiles, snails, birds, and mammals when they feed on land. In agriculture fields and wetlands, rhizomes, roots, tubers, and other parts of emergent plants, other molluscs, eggs of birds, small fish, and amphibians are also consumed. The exact composition of the diet differs by season, location, and availability.

A few patterns emerge from the large variety of foods ingested, but further research is needed to validate them: shorter-billed species eat in drier uplands, while longer-billed species eat in wetlands.

Breeding

Cranes are notorious for being monogamous breeders, forming long-term pair relationships that can last a lifetime. Pair bonds begin to form either in the second or third years of life, but many years pass before the first successful breeding season. Initial breeding attempts are frequently unsuccessful, and in some cases, newer pair connections disintegrate (divorce) as a result of the failed breeding attempts.

Pairs that have a long history of successful reproducing stay together as long as they continue to do so. In Florida, in a study of sandhill cranes, 7 of the 22 pairs studied remained together for an 11-year period. Of the pairs that separated, 53% were because of the death of one of the pairs, 18% were because of divorce, and the fate of 29% of pairs was unknown. Acoustic monitoring (sonography or frequency analysis of guard and duet cries) in three breeding locations of common cranes in Germany yielded similar results over a ten-year period.

Cranes vs. Flamingos

Cranes and flamingos are the most distant relatives. Oddly enough, the closest relatives of the flamingoes -based on molecular evidence - turn out to be, of all the things, grebes - birds that do not look anything like flamingos. Flamingos and Grebes, together, appear to be components of an old branch of the avian family tree.

Generally, having long necks and long legs does not make birds close relatives. Cranes are not related to the herons either - herons are very close to pelicans, as per the molecular evidence. The same body types have evolved over and over again in response, it seems, to the same environmental pressures.