Cranes


Cranes

Cranes

CranesCranes are birds of the superlatives. Some stand nearly 2m (6.6ft) high, making them Earth’s tallest flying birds. Some fly over the Himalayas at more than 9 000 m (3000 ft) above sea level and are among the highest-flying birds. Not only are cranes among the oldest groups of birds, dating back some 6o million years. But captive cranes have lived into their 70s and 80s. Their calls are among the loudest, and cranes’ beauty and grace are difficult to surpass. Unfortunately, the cranes are also among the most endangered families of birds. Mankind is entirely responsible frothier decline.

Generally, cranes are birds of the open marshlands, grasslands, and agricultural fields. Most species usually nest in secluded areas of shallow wetlands, the exception being the two species of Anthropoids, which often nest in grasslands or semi-desert areas.

Cranes have long, powerful, straight beaks and long necks and legs. They are heavy sets and have loud, shrill calls that carry for several kilometers. The windpipe Several species are lengthened by coiling within the breastbone and it is believed that this extended organ amplifies the calls. Cranes fly with their neck extended forward. Usually, the legs are stretched straight beyond the short stubby tail during flight. But in cold weather flying cranes fold their legs, so the feet are tucked under the breast feathers. Although they are predominantly aquatic birds, their feet are not webbed, and cranes are restricted to the shallows where they breed, search for food, and rest during the night. Only the two species of crowned cranes roost in trees.

The crowned cranes are also the “living fossils” among the cranes. In the remote Eocene (54-38 million years ago) these loose-plumed birds with enormous, gaudy crests, flourished in the northern continent for millions of years before the Earth cooler and the cold-adapted cranes evolved. Thrice Age restricted the range of the crowne: cranes to the savannas of central Africa where tropical conditions were maintained during the period when the northern continent duet, during which the male and female calls are distinct yet synchronized.

In most species, the male emits a series of long, low calls. With each male call the female pro-dukes several short, high-pitched calls. The display identifies the sex of each of the birds, a factor that assists in the development of the pair bond. However, after a stable relationship is established between two cranes, the unison call primarily functions as a threat. At dawn, the crane pairs announce their territory with a unison call and as the display is heard by neighboring pairs, the same is returned, so that for kilometers an extended chorus of crane calls announces occupancy of real estate.

CranesThe reproductive states of two members of a stable pair are synchronized by their bodily cycles, the weather, the length of daylight, and elaborate displays such as nuptial dances and unison call. Cranes begin copulating several weeks before eggs are laid. For fertility to be assured, a female crane must be inseminated two to six days before an egg is laid.

At a secluded spot within the wetland breeding territory, the pair constructs a platform nest. Crowned cranes often lay a three-egg clutch, while other cranes lay two eggs, with the exception of the Wattle crane which more frequently lays a single egg.

Male and female cranes share incubation duties. The females usually incubate during the night, while the male does so during the day. The bird that is not on the nest usually feeds at a considerable distance from it, sometimes in a “neutral area” in company with other cranes. Within the 28-36 day range, the duration of incubation depends on the species and the parents’ attentiveness at the nest. Crowned cranes do not initiate incubation until the clutch is complete, and their eggs hatch simultaneously. Other cranes begin incubation as soon as the first egg is laid, and successive chicks hatch at one- or two-day intervals.

CranesCrane chicks are well-developed when they hatch (precocial) and follow their parents around the shallows and neighbor-in uplands until they develop flight feathers at 2-4 months of age. The larger and tropical species, such as the Wattle and Saruscranes, have a longer pre-fledging period than do species such as the Siberian crane, in which the short arctic summer limits the period when food is available for the fast-growing chicks. Although all eggs usually hatch, many chicks die, and most of the endangered species usually only rear a single chick per breeding effort. Once fledged, the chicks remain with their parents until the onset of the next breeding season. Migratory cranes learn the migration path by accompanying their parent’s thousands of kilometers south to traditional wintering grounds. Foraging behavior is also learned, while the form of displays is generally predetermined.

In North America, the Whooping cranes have recovered from 14 birds in 1941 to approximately 75 birds in the “natural range” flock, and a total, including captive birds, of about 140 cranes. The Siberian crane is now reduced to fewer than 900 individuals, Black-necked cranes to fewer than 500, and Red-crowned cranes to fewer than i3O0o birds in the wild. Fortunately, cranes are appealing birds, and recent efforts in many Asian countries have resulted in the protection of wetlands critically needed by cranes. But crane hunting continues in Canada, Afghanistan, Pakistan, and the United States of America, and the pressures on the wetlands for man’s use increase as human numbers soar.

Although many cranes are severely endangered, they respond well to protection and management. In an effort to ensure their survival, captive flocks of the endangered species are now being established at several zoos and specialized crane research centers. Foremost in captive breed-in has been the Patient Wildlife Research Center in Maryland, in the USA. A captive
A Flock of Whooping cranes has been established at the Patient by collecting one egg from each nest of the wild cranes containing two eggs.

CranesThe eggs laid by the captive birds are now transferred from them and sub-statute for those in nests of Sandhill cranes in Idaho. The Whooping cranes reared by foster parents migrate south with them and learn to feed in the agricultural fields with the Sandhill cranes. The 30 or so birds con-stetting this new population show little interest in breeding with Sandhills, but the pairing has not yet occurred between the Whoppers.

The limpkin is the only member of the New World family Armada. It has anatomical features in common with the cranes and has a digestive system like that of the rails–in general appearance, it is not unlike a very large rail. Without exception they are birds of the ground or water level, running or swim-Ming through a wide variety of habitats. Their distribution includes every major, landmass (except Antarctica), and they are remarkable for colonizing even remote islands.

Rails are inhabitants of rather specialized, patchy habitats such as river floods plain sand forest clearings. Such habitats may be here one year and gone the next, and the life histories of the rails arc adapted to these circumstances. All rails are stout-legged and short-winged, adapted for traveling swiftly through dense, low vegetation.

Rails fall, with some degree of overlap, into three groups the long-billed rails, the crakes and gallinules, and the coots.

The long-billed rails are characterized by medium to long, often slightly down-curved bills. This is a generalist tool that can be pushed into mud, as the Water and Virginia rails will do when searching for worms, or used more powerfully in smash-in eggshells, crushing horny grasshoppers, or even killing the occasional frog or duck-ling. in some of the larger rails, the bill is even more of a hatchet. Larger vertebrates, even rats, may make a meal for the sturdy New Guinea flightless rail, one of the little flightless birds to hold its own against man’s introduced exterminators.

The social organization and behavior of most of the long-billed rails is a mystery. Most species, even the larger ones, seem tube able to breed in their first year another adaptation to temporary habitats and territoriality seems to be the rule. The rails are a vocal group, forced to defend their densely vegetated territories by voice, and many species seem to indulge in “dieting” in which the male and female of a pair each contribute to a coordinated song. This habit may inform potential intruders that there are indeed two adults in residence and that any incursions will be met by effective resistance.

The crakes and gallinules have shorter bills. Some species look rather like partridges, although they always have the slim body necessary for moving efficiently through dense vegetation. Their bills are not long enough to probe into the mud and they depend more on surface foraging for smaller invertebrates and seeds. Some, like the endangered taka he of New Zealand, are almost entirely vegetarian. Consequently, they have no great dependence on marshland soft ground, although they may certainly be found in those places, sometimes even trotting about on lily pads like the unrelated jacanas (Charadriiformes), and have therefore exploited a wide range of habitats.

The corncrake, for instance, Isa a bird of coarse grasslands in the northern Palaearctic (Europe, North Africa, and northern Asia) and was formerly communal over Europe, occurring in many of the habitats where partridges are common today. Although very rarely seen, this shy bird could easily be detected by its distinctive call sounding like a knife being scraped over the teeth of a comb. Changes in the timing of hay-mowing, and perhaps the introduction of pesticides, have eliminated this species over much of its former range, although it is still one of the more easily found crakes. However. We know almost nothing of its biology. Like many of its
Spectacular leap for food. A Water rail shoots up a meter (3.3ft) from the water’s surface to seize a dragonfly.

V Snails are not a delicacy but form the major part of a limpkin’s diet. This bird holds the freshwater snail in its bill before taking its tithe bank, holding it on the mud with one foot
And extracting the animal from its shell with its bill. Drainage of marshes removes the snails, and also the limpkins which feed on them.

In the swamps and shaded areas which are its principal home, the presence of the limpkin may be detected by the many con-spacious empty shells of large freshwater snails (Panacea caliginous) that it leaves on the muddy banks. To secure its food, the long-legged limpkin wades in shallow water, probing with its long, laterally compressed bill slightly down-curved at the tip. When it finds a snail, it carries it to the shore and sets it in the mud with the shell opening facing upwards, holding it there with its long toes tipped with long, sharp claws. With great dexterity, the bird quickly removes the horny operculum that protects the snail, pulls out the mollusk, and swale-lows it.
Limpkins walk rather slowly with a curious undulating tread that gives the impression of lameness or limping, from which the common name is derived. Although they lack webs on their feet, limpkins swim well. In flight, the head and long slender neck are extended with the feet and legs projecting behind, in the manner of a crane.  

Although the limpkin also takes frogs, lizards, and worms, the snail accounts for such a high proportion of its normal diet that it cannot exist without it. Where marshes have been drained, the snails have dies-appeared, and with them the limpkin. In the United States of America, the bird is now well protected and, since the Everglades and Lake Okeechobee in Florida are too vast to drain, it is likely that the species will always survive there. 

Trumpeters are non-migratory, ground-dwelling birds that live in small to sizeable flocks in the tropical rainforests of South America. The three closely related species are about the size of a domestic chicken. They may be distinguished by the color of their innermost flight feathers, inner wing coverts, and lower hacks, which. Are gray in the Gray-winged trumpeter, white in the Pale-winged trumpeter, green in the Dark-winged trumpeter.

The head in all three species appears small in relation to the body, and the large dark eyes give the head its “good-natured” expression. When it is standing, the trumpeter’s very short tail is almost completely hidden by the outer webs of the secondaries. The typical hunch-backed appearance has led to trumpeters being given the nickname, in Surinam, of” Kamee-kameez” (”camel-back”). The soft feathers on the head and long neck have an almost fur-like quality. The bill is short, stout, and slightly curved.

Trumpeters have at least two different calls, a flock call, and a threat call. The flock call is a booming “oh-oh-oh-oh.”The long drawn-out part of this call is delivered with the bill closed, which causes the sound to reverberate within its body. The threat call is a loud cackle, or trumpet-in, from which the group takes its name. Trumpeters have the ability to run fast but are rather poor fliers. At dusk they fly up rather laboriously, on deeply-rounded wings, some 6-9m (2o-3oft) to roost in the forest trees, where they form noisy, quarrel-some groups.

CranesDetails of the trumpeters’ breeding cycle are still imperfectly known. At the begin-nine of the breeding season, large flocks are reported to gather in clearings in the forest where the ground is smooth and free of Obstacles. Here, they perform elaborate and noisy courtship dances, which involve much strutting and leaping and sometimes even somersaulting in their excitement. After mating, a pair of trumpeters will select a nest site which may consist of a hole in a tree, or on the ground. The average clutch size is about seven, and it is the female that incubates. When the young hatch they are covered with thick, black down with labor-ate pinkish streaks. They do not stay long in the nest and are soon running about after their parents. Trumpeters are reported to make good eating. This, combined with the fact that they are unwary birds and poor fliers, has made them easy targets for hunters who, in income parts of their former range, have hunted them to extinction. 

Rails are a large but little-known family which might generously repay further efforts to tease apart the details of their lives. Most species inhabit remote areas a few, especially the coots, are more common Without exception they are birds of the ground or water level, running or swim-Ming through a wide variety of habitats. Their distribution includes every major landmass (except Antarctica), and they are remarkable for colonizing even remote islands.

Rails are inhabitants of rather specialized, patchy habitats such as river floods plain sand forest clearings. Such habitats may be here one year and gone the next, and the life histories of the rails are adapted to these circumstances. All rails are stout-legged and short-winged, adapted for traveling swiftly through dense, low vegetation.

Rails fall, with some degree of overlap, into three groups the long-billed rails, the crakes and gallinules, and the coots.

CranesThe long-billed rails are characterized by medium to long, often slightly down-curved bills. This is a generalist tool that can be pushed into mud, as the Water and Virginia rails will do when searching for worms, or used more powerfully in smash-in eggshells, crushing horny grasshoppers, or even killing the occasional frog or duck-ling. In some of the larger rails, the bill is even more of a hatchet. Larger vertebrates, even rats, may make a meal for the sturdy New Guinea flightless rail, one of the little flightless birds to hold its own against man’s introduced exterminators.

The social organization and behavior of most of the long-billed rails is a mystery. Most species, even the larger ones, seem tube able to breed in their first year another adaptation to temporary habitats and territoriality seems to be the rule. The rails are a vocal group, that is forced to defend their densely vegetated territories by voice, and many species seem to indulge in “dieting” in which the male and female of a pair each contribute to a coordinated song. This habit may inform potential intruders that there are indeed two adults in residence and that any incursions will be met by effective resistance.

The crakes and gallinules have shorter bills. Some species look rather like partridges, although they always have the slim body necessary for moving efficiently through dense vegetation. Their hills are not long enough to probe into the mud and they depend more on surface foraging for smaller invertebrates and seeds. Some, like the endangered taka he of New Zealand, are almost entirely vegetarian. Consequently, they have no great dependence on marshland soft ground, although they may certainly be found in those places, sometimes even trotting about on lily pads like the unrelated jacanas (Charadriiformes), and have therefore exploited a wide range of habitats.

CranesThe corncrake, for instance, Isa a bird of coarse grasslands in the northern Palaearctic (Europe, North Africa, and northern Asia) and was formerly communal over Europe, occurring in many of the habitats where partridges are common today. Although very rarely seen, this shy bird could easily be detected by its distinctive call sounding like a knife being scraped over the teeth of a comb. Changes in the timing of hay-mowing, and perhaps the introduction of pesticides, have eliminated this species over much of its former range. although it is still one of the more easily found crakes. However, we know almost nothing of its biology. Like many of its group, the corncrake is suspected to be monogamous. raising usually one brood per year, and being territorial.

Some cranes and gallinules may have quite complex, even fascinating breeding systems. In the moorhen, the offspring of early broods sometimes remain with the parents through the raising of later broods in the same year and even help to feed their younger siblings. This also happens in the Purple swamp hen or pucker of New Zeal-land, although this species shows more complicated social behavior several females may lay in a single nest, and each female may copulate with many of the males in the breeding group; the whole group portico-pates in parental care and territory defense.

Unlike the other rails, the coots are truly aquatic birds, able to swim and dive well using their generously lobed toes, and rarely found far from the water. They can thus colonize deep and desolate waters, such as the high-altitude lakes of the Andes where the two largest and grandest species, the Horned and Giant coots, make their home. Because they gain their protection from open water rather than dense vegetation, they have less need for the slim profiles of their relatives and are altogether stouter birds. They are omnivores, eating mainly plant material in winter but adding the seasonally abundant water insects to their Diet in spring and summer. The chicks are fed almost exclusively on insects for the first part of their lives, only gradually changing over to a diet of vegetation as their bodies, and intestines, grow larger and capable of coping with this relatively indigestible food.

Again unlike most rails, the coots can be gregarious, especially during winter when flocks of thousands of, for example, European coots may gather on large lakes and even the sea coast. The function of these gatherings is uncertain, but they do provide an excellent opportunity for some endive duals to exploit their weaker subordinates. All coots return to the surface before eating their food haul, and this gives a chance for food stealing to occur a bird may hardly break the surface before its pondweed is snatched away by one of the pirates. During winter some individuals obtain most of their food in this way and thus avoid the costs and difficulties of deepwater diving.

All the rails have stout, well-muscled legs with three forward-facing toes and one hind toe, emerging from the leg slightly higher than the others and used as a brace during walking. The feet are important weapons in the struggle to gain a breeding territory. In the Asian water cock these male combats make spectacular sport and the birds are carefully cultivated, like champion fighting cocks. The legs and feet of newly hatched rails grow faster than most other body parts because becoming mobile is of the utmost urgency in these chicks.

Rail chicks are very unusual among birds in being mobile and leaving the nest soon after hatching, but being fully dependent on parents for feeding for at least the first few days of life. Young coots may obtain at least some of their food from parents for up to 6o days after hatch-in, although in many rails and crakes this dependency is much briefer. But in all species chicks must accompany the parents around the territory in order to solicit food thus the importance of early mobility.

In most rails the first laid egg hatches at least one day earlier than the last, a time-lapse that introduces differences between siblings within the brood. The eldest chick may already be sufficiently strong and agile to capture its insect food at a time when the youngest of the brood is still struggling from the egg. These differences persist throughout the dependent period, and the younger chicks often starve in competition with larger siblings for food from their parents.

This feature of breeding biology, which at first sight seems to diminish the reproductive success of the parents, may have evolved as a mechanism to match the size of the brood to an unpredictable and variable food supply. In part, the greater success of some chicks in obtaining food is due to the tithe inability of the younger chicks to follow their parents as they swim around the territory.

CranesBut, at least as important, parents tend to have preferences for particular chicks foremost of the time each parent is accompanied only by their “favorite” chick or chicks. The way in which parents maintain this division is astonishing. If a “wrong” chick approaches an adult, it is seized by the headland and shaken about before being dropped back into the water. After this treatment, the chick usually retreats, indeed the longer it’s shaken the longer it stays away from that parent!

The rails interact with a man very little indeed. Farmers have sometimes accused certain gallinules, such as the Gray moorhen, of eating spring crops, although the evidence points to these losses being very small. Some species are killed for food, especially the coot in Eastern Europe, where each hunter takes an average of three or four per year. Radii pose, were a problem, fur Man only in their conservation. They tend to live in habitats that are vulnerable. Indeed, several species have become extinct within living memory and the prospect number of others does not look promising.

See more: Button Quails

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