Rallies

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Rallies
Common pond rail (Gallinula chloropus)

Common pond rail ( Gallinula chloropus )

Systematics
Sub-stem : Vertebrates (vertebrata)
Superclass : Jaw mouths (Gnathostomata)
Row : Land vertebrates (Tetrapoda)
Class : Birds (aves)
Order : Crane birds (Gruiformes)
Family : Rallies
Scientific name
Rallidae
Vigors , 1825

The Rallen (Rallidae) are a family of the crane birds (Gruiformes). Depending on the scientific opinion, they comprise between 131 and 165 species . Of these, at least 22 species have been extinct since 1500 . An unusually large number of rail species are endemic to oceanic islands and have lost their ability to fly there .

features

Appearance

Rails are small to medium-sized ground birds, the bodies of the birds are narrow and appear compressed. The spine is very flexible, which, in combination with the long toes, enables it to live as a panty in very dense vegetation on often poorly stable ground. The size is between 12 cm and 63 cm, the weight between 20 g and 3 kg. The smallest species is the American slate rail , the largest the New Zealand takahe . The Atlantis rail , the smallest flightless bird in the world, also belongs to the railing family ; it has a body length of 13 to 15 cm.

The plumage colors are predominantly brown, gray and black, but many rails are also very conspicuous, colored with brightly colored and iridescent parts of the plumage. The water-repellent plumage is soft and loose. With some genera a mostly brightly colored forehead shield is noticeable. Most species show little or no sexual dimorphism in terms of size, weight and plumage. Males are usually slightly larger than females, but the difference is usually so small that it cannot be used in field ornithology. Only in the case of a few representatives of the family do the sexes differ significantly. This mainly includes island shapes.

Toes of the coot

The four toes of the anisodactyl foot are long, in some species they are even extra long. With their long toes, rails also find a hold on muddy ground and floating vegetation. In order to adapt to their aquatic habitat, some species have swimming flaps on their toes. The legs are often brightly colored.

The beak shapes are very variable in view of the different eating habits. Species that feed mainly on carnivore mostly have relatively long, pointed and narrow beaks, the last third of which are slightly bent downwards; the beaks of omnivorous or vegetarian species are shorter and stronger and sometimes also noticeably high. The nostrils of many rails have flaps that reflexively close when the beak is immersed in water or in the substrate. The well-developed mucous cells of the olfactory cavity and the large olfactory brain indicate a well-developed olfactory ability of the rails. A rump gland is developed in all species, some halophilic or halotolerant species have salt glands .

The flyable rails usually have eleven hand swings, with the flightless ones there was a reduction to eight. The wings are relatively short and rounded. Very few rails like to fly, mostly they run away and hide in the dense undergrowth of their habitats. Even if disturbances force them to fly open, they quickly fall back into cover. Nevertheless, some rails are downright long-distance migrants , which usually fly close to the ground, fast and persistently. Abrupt steering maneuvers are not possible due to the short tail. All rails change their plumage in a full moult after the breeding season.

32 species are incapable of flight, all of which are island endorses. In these, the flight muscles have atrophied in the course of evolution, since the ability to fly was no longer used due to the absence of predators . The short tail has between 6 and 16 control feathers. It can be very short, especially in flightless species.

voice

Rails are very call-happy birds that have a diverse vocal repertoire. Often these are monosyllabic, creaking or creaking sounds that are often played for hours, primarily in the twilight and night hours. Also monosyllabic, so-called explosive sounds are often heard by representatives of the family. The presence of rails can often only be determined by their voice.

distribution and habitat

Giant coot in the Andes of Chile

The rails are spread all over the world except for the Antarctic and the Arctic. The focus of their distribution is in the tropical and subtropical areas of Africa and Asia, but some species penetrated into subpolar areas in both the northern and southern hemisphere. In addition, despite their modest flying skills, the family has colonized a great many, including extremely remote islands, in all the world's oceans. Endemic species quickly developed on these; some of them lost their ability to fly. 9 species breed in Europe .

The majority of the railings live on the water, close to water, or at least in humid biotopes, but the adaptable birds were also able to colonize drier, water-remote habitats. Extreme arid areas and deserts are, however, always avoided. Some also succeeded, such as the giant coot ( Fulica gigantea ), in occupying breeding spaces at great heights ( 4000  m and more). But the corncrake is also found in its Central Asian distribution areas at altitudes of up to 3000  m . Common to the habitat of the railings is a dense, at least knee-high, ground vegetation; aquatic species also prefer areas where the open water surface borders on densely overgrown bank zones.

Way of life

activity

Most of the rails are hidden solitary animals. Especially outside of the breeding season, some types of railing also form large associations, so coots can live in groups of up to 10,000 individuals.

Rails are primarily crepuscular. As a rule, they rest at night, but many species are also around on moonlit nights. The migratory birds under the rails also prefer to migrate at night. In this way they escape birds of prey more easily, which, as relatively clumsy fliers, they could hardly avoid. There are some types of railing that call, especially at night; but these species also show greater activity during the day. No type of rail is really predominantly nocturnal.

To rest, rails usually retreat into the protection of dense vegetation. Some forest-dwelling rails also seek out the branches of the trees for this purpose.

nutrition

Rails are omnivores. There are no species that feed exclusively on plants or animals. Many are opportunists who will take whatever food is available. For some, however, a certain part of the diet predominates. Species with long, thin beaks poke the muddy ground for worms and seeds. Species with short, unspecialized beaks feed on the ground or the surface of the water. Particularly strong beaks are suitable for digging up roots and tubers.

All green parts of the plant, roots, seeds and, to a lesser extent, fruits are eaten in vegetable food. The animal diet includes worms, mollusks, crustaceans and arachnids as well as insects and their larvae. Larger rails can also eat small fish, frogs or tadpoles.

All rails swallow gastroliths . Mainly herbivorous species ingest them in particularly large quantities.

Reproduction

The Corn Corn has a different, polygynous reproductive strategy

The most common reproductive strategy in rallen is monogamy . The rails are tied to a partner for at least one breeding season, sometimes for several years. Polygamy is known of only five species, including the corn corn that lives in Europe . The reproduction described below applies to most rallen; some notable exceptions are mentioned at the end of the section.

At courtship , males are particularly happy to shout. If a female is attracted, a courtship ceremony takes place, which is not very pronounced in most species. This includes cleaning each other, handing over food or hunting each other as a prelude to copulation. There are more elaborate gestures in some species such as the water rail, in which the male lowers his head during courtship, raises his tail and spreads his wings. While the courtship of some species can take place on the water, mating is always carried out on land.

The nest is built from all available parts of the plant. It is usually hidden in thick vegetation. This is then also stepped down or pulled down in order to cover the nest with a roof more effectively. Some species build floating nests on the water. Noteworthy here is the giant coot , which builds 3 to 4 m tall rafts that can protrude up to 50 cm from the water.

5 to 10, and in some small species even up to 19 eggs are laid. These are incubated for 13 to 20 days. Both partners breed and take part in the rearing of the young, but the female's share in these tasks is usually greater. The young are refugees . They leave the nest after three days at the latest, but often return at night. Since their bodies cool down slightly at first, they are dependent on the warmth of a parent bird. In the first days of life, young rakes are still fed, only after a week or later do they start to eat independently. Rallen fledged at four to eight weeks. The legs of young rails grow particularly quickly and therefore appear particularly disproportionate. In contrast, the wings grow the slowest.

As a rule, the young claws are eventually driven away by the parent birds. In some species they stay in the family to help with a subsequent brood and rearing of young.

There are a few notable exceptions to monogamous reproduction. The Corn Crake is polygynous ; Males mate with several females in the overlapping territories and stay with one of these until the end of the breeding season, while the other mated females raise their young alone. Conversely, polyandry prevails in the African gray-throated marsh grouse - here the female is the more active partner in courtship, but it does not participate at all in brood and young rearing, but leaves these tasks entirely to the male. In the Australian Papuan moorhen up to seven individuals breed together; Males mate with each female in the group, and all females lay their eggs in a common nest. A similar reproduction strategy is found in the Asian-Australian populations of the purple grouse , while this species is monogamous in the other parts of its range.

The chestnut rail of New Guinea is also noteworthy . Although it lives in monogamy, it only lays one single egg, which is disproportionately large and is incubated for an extraordinarily long time (34 to 37 days).

Evolution and systematics

Tribal history

The molecular clock suggests that the claws separated from the other crane birds about 86 million years ago during the Upper Cretaceous , but the oldest fossil finds are much younger. There are already fragmentary fossil records from the Eocene , but these cannot be clearly assigned to the rails. Certainly this only succeeded from the Oligocene . Belgirallus oligocaenus from the early Oligocene is the oldest known fossil that can be safely assigned to the railing. Many representatives of the modern genera are already known from the Pliocene and Pleistocene .

Systematics

Rails are assigned to the crane birds (Gruiformes). Since the representatives of this order are so diverse, the togetherness was often questioned in the past; Rails were therefore also placed in a separate order Ralliformes or even assigned to the plover-like . The relationship between railing and cranes is now scientifically proven. The likely sister group of walnuts are the rush walks (Heliornithidae), and this common taxon is in turn closely related to cranes, trumpeter birds, and walnut cranes .

Traditionally, Rallen were divided into three subfamilies: the "real" Rallen (Rallinae), the pond and marsh fowl (Gallinulinae) and the coot (Fulicinae). The allocation was made according to the way of life: predominantly land-dwelling rallen were assigned to the Rallinae, water-dwelling to the Fulicinae, and the Gallinulinae represented a transition between the two. This subdivision does not reflect the actual relationships, however.

In 1973 Storrs Olson found that the African red-footed rail ( Himantornis haematopus ) is a morphologically particularly different species, which in many features is more like the trumpeter birds than other railing; He therefore set up a separate subfamily Himantornithinae for them, which he compared to all other Rallen. In contrast, Sibley and Ahlquist saw the African genus Sarothrura as a particularly original genus and placed it completely outside the racks in the family Sarothruridae , which was confirmed by Hackett and colleagues in their phylogenetic study in 2008. Livezey's analyzes, on the other hand, again gave the red-footed rail the special position and viewed all other rails as monophyletic ; the genus Himantornis is therefore not to be classified with the rails .

The following genera and species are usually included in the rails. The list follows the Handbook of the Birds of the World , some extinct species have been added:

Bandage rail
Water rail
White-breasted keel rail
Spotted Moorhen
Purple chicken
Comb coot

Rails and people

use

The Wekaralle is sometimes viewed as a pest in New Zealand

Despite their richness in species and diversity, most of the rallen are not very well-known birds and have at most a local economic importance. Rails are hunted in many parts of the world. The less hidden species, especially coots, are particularly under pressure to hunt. The coot has been shot in large numbers in Europe and North America in the past; However, the focus was on “sport” and not the use of meat or feathers. In Central Asia, on the other hand, coots are hunted and eaten. In the past, water rallies and corn kings were tracked down with dogs, and these were also eaten. Today rails no longer play a role on people's menus, at least in Europe and North America. Rallen's eggs are collected and eaten regionally; This is common, for example, in Asian moorhen populations or in the nests of the South American giant coot.

There have probably never been any serious attempts to domesticate rails. However, there are regional cases in which rails are kept half-tame. This applies to the South American Ypecaharalle or the subspecies of the Union Rail, which is native to the Cocos Islands . The tap is used in Bangladesh for cockfighting .

Rails that fall into fields and eat the crops there are considered pests. The purple chicken in South Asia and the pygmy sultans in South America are said to be particularly problematic in rice fields . A special case is the New Zealand Wekaralle, which follows people into the cities and villages as cultural followers and kills chickens and ducks here.

Threat and protection

An unusually large number of rail species became extinct in historical times. This is mainly due to the fact that many Rallen have become islanders and have lost the ability to fly. After humans brought dogs, cats and rats to the islands they inhabited, the populations quickly died out. In the case of the Laysan rail, the introduction of wild rabbits was causal; the rabbits ate the grass so far that the previously common rail no longer found a nesting opportunity and died out. The majority of the still existing flightless rails are also threatened.

Other rail types are threatened by changes in their habitats. In particular, residents of swamp forests with small distribution areas such as Wetmoreralle and Kubaralle are affected by this.

Some rails were saved from extinction by intensive protective measures. This applies to the Takahe of New Zealand, which was now considered extinct; After the rediscovery, parts of the population were relocated to small islands off the coast that had previously been freed from rats and cats. The guamralle was exterminated on Guam by the introduced brown night tree snake , but was bred in a conservation program in several zoos in the USA and finally released on the island of Rota , where it is now successfully breeding; since this island is not the natural range of the Guamralle, the species is still considered extinct in the wild.

Sources and further information

Sources cited

Most of the information in this article is taken from the source given under literature; the following sources are also cited:

  1. ↑ Gerald Mayr: A rail (aves, rallidae) from the early oligocene of Germany . In: Ardea 2006, Vol. 94, No. 1
  2. ↑ a b B.C. Livezey: A phylogenetic analysis of the Gruiformes (Aves) based on morphological characters, with an emphasis on the rails (Rallidae) . In: Philosophical Transactions of the Royal Society B: Biological Sciences 1998, Vol. 353 (1378), pp. 2077-2151
  3. ^ SL Olson: A Classification of the Rallidae . In: The Wilson Bulletin 1973, Vol. 85, No. 4, pp. 381-416
  4. ^ CG Sibley and JE Ahlquist: Phylogeny and Classification of Birds . Yale University Press, 1990
  5. ↑ Hackett et al .: A Phylogenomic Study of Birds Reveals Their Evolutionary History . Science 27 June 2008: Vol. 320. No. 5884, pages 1763-1768 doi : 10.1126 / science.1157704
  6. ↑ George Sangster, Juan Carlos Garcia-R and Steve A. Trewick. 2015. A New Genus for the Lesser Moorhen Gallinula angulata Sundevall, 1850 (Aves, Rallidae). European Journal of Taxonomy. 153: 1-8. DOI: 10.5852 / ejt.2015.153

literature

Web links

Commons : Rallen  - album with pictures, videos and audio files
Wiktionary: Rallen  - explanations of meanings, word origins, synonyms, translations
This version was added to the list of articles worth reading on July 8, 2009 .