Stilt claws
| Stilt claws | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Monias stilt claw, male |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Mesitornithidae | ||||||||||||
| Wetmore , 1960 |
The stilt claws (Mesitornithidae) are a family of claw-like birds consisting of only three species in two genera . They are endemic to Madagascar and are classified as endangered by the IUCN .
features
anatomy
Stilt claws are pronounced ground dwellers with short, round wings and very strong legs and feet. The body length is about 30 cm, of which about half is the tail. The head appears quite small in comparison to the body, the beak, which is strong at the base, is a few centimeters long and only slightly curved in the two species of the genus Mesitornis , in the Monias stilt claw the beak reaches about the length of the head and has a clear, sickle-shaped shape Bend on. Stilt claws do not have a humeral gland , nor do they have a goiter . They have powder down due to the lack of the ore gland .
coloring
The three species are all more or less brown feathered, the proportion of gray and white feathering, which occurs mainly on the belly and chest, varies. Two of the three species, the short-footed stilt claw and the Monias stilt claw, show dark spots on the otherwise light-colored chest and abdominal plumage. The eye is surrounded by a narrow ring of bare skin, behind or immediately above the eye a light strip runs along the neck to the nape of the neck. The coloring of the legs is pale red or olive. Only the Monias stilt claw shows a sexual dimorphism .
Move
Stilts keep the back parallel to the ground, while walking slowly the head is stretched forward in two ways and then forms a line with the spine. Only the Monias stilt claw carries the head a little higher than the rest of the body at times. The tail feathers are extremely rarely erect, they form a line with the head and body and thus contribute to the streamlined impression of the birds. The passage never appears hasty, stilt claws only run when danger threatens or prey is being pursued. Characteristic for the movements of the stilt claws are a nodding of the head that is differently pronounced, depending on the species, after each step and a brief rocking of the tail feathers. In general, all three species rarely fly, only to escape or to get to a safe place to sleep in a tree, the wings are used with fast, loud flapping. The flight ability is only slightly developed, so stilt claws rarely cover more than 20 to 30 meters in the air.
voice
The animals have a wide range of sounds that can be used individually as signals for communication within a group, but can also be expanded into chants. Males and females of the short-footed stilt rail and the monochrome stilt rail sing a duet initiated by the males, lasting around 30 seconds, in which they sing different parts. While males recite shorter stanzas alone, females almost never sing alone. Singing stilt claws induce groups in neighboring territories to also initiate a chant. In addition, sometimes only the females of neighboring groups sing to each other.
The singing of the monochrome stilt rail consists of very loud, often repeated and merging calls that sound like " hütjühütjühütjü ". The singing can most often be heard in the early morning hours shortly before and after sunrise, and it is not uncommon for it to be intoned after waking up in the sleeping place. In the course of the day the frequency of the singing decreases, after the late morning the birds are completely silent until the next morning. During the breeding season , the Monias Stelzenralle sings more often and longer than outside of the breeding season, a sequence of sounds that sounds like " züzüzü zizizizizi ürr " is then strung together to form stanzas lasting 30 to 45 seconds. In the course of a stanza, the initially audible " züzüzü " changes into a " zizizi ". It is assumed that the " ürr " is contributed by a second individual, so this species also sings a duet. Since the short-footed stilt rail is the best researched stilt rail in all aspects, other vocalizations are known, especially from this species. While they are eating, young birds call their parents with a chattering contact call that sounds like " pop-pop-pop "; adult birds keep in contact with one another with a " bub-bub-bub " that sounds like chattering teeth for about five seconds . This sound is also used as a greeting between individuals. After a mating, a short, very loud utterance that sounds like " quiiquiiquii " is made.
Single-color stilts keep in contact with each other with a gentle " chuck ". Little is known about the sound uttered by the Monias stilt rail , sounds uttered by chicks of this species are similar to the calls of chicken chicks. The alarm call of all stilt claws is a hissing or chirping, sharp sound.
distribution and habitat
Single-color stilt claw : orange;
Monias stilt claw : blue
All stilt claws are endemic to Madagascar , where they occur in the increasingly scarce forested areas and dry bush savannahs. Dense primary forests as well as light secondary forests and more open, tree-lined areas are inhabited. Plantations and other man-made plantings are avoided by stilts. The preferred habitat of the species of the genus Mesitornis is dense forest, the Monias stilt rail populates the more open landscape. Originally, the three types of stilt claws were considered allopatric , because each ecosystem of the Malagasy lowlands seemed to be inhabited by just one different species. The single-color stilt rail seemed to exist exclusively in the wet forests to the east, the short-footed stilt rail only in the western dry forests and the third species, the Monias stilt rail, in the more open spiny forests of the southwest. However, this classification can only be maintained to a limited extent, since in 1990 a pair of the short-footed stilt rail was discovered in the easternmost part of the Madagascan wet forest, which consequently inhabits a habitat together with Mesitornis unicolor . However, there is no further evidence in this habitat. Stilt claws are largely true to location. All species do not occur in the entire area of the existing and suitable habitat . This may be due to poor flight ability, which makes it impossible to cross wide rivers. Areas with a thick layer of leaves and sparse ground cover are visited by the birds with preference, as they find abundant prey organisms there as ground-dwelling insectivores.
Grazing area and migration behavior
Short-toed stilt claws defend territories that are 2 to 15 hectares in size. During a day, the birds cover distances between 500 meters and one kilometer within their territory. The sleeping places are often changed, but sometimes used repeatedly. Similar values and behaviors are assumed for the other two species.
Only the one-color stilt rail goes on hikes. It probably migrates at altitudes below 500 m in winter and lives in higher areas during the breeding season.
Way of life
All species of the Mesitornithidae family are considered to be shy and cautious and are therefore difficult to observe in most of their range, the most seldom to be observed and the least researched is the single-colored stilt-claw, which occurs in very low population densities and whose habitat is largely inaccessible .
activity
Stilt claws show the greatest activity in the early morning hours and early evening. During the hot midday hours, the animals rest in a shady place. All three species are almost exclusively on the ground, trees are only visited to sleep or nest there. If possible, the birds climb into a tree to find their breeding or roosting place over climbing plants or lower vegetation, very rarely they just fly up. No information is available about the comfort behavior of the stilts.
Social and antagonistic behavior
Depending on the species, stilts form groups of at least one breeding pair and sometimes their offspring. In the case of the short-footed stilt rail , an association usually consists of the parent animals, apparently lifelong monogamous , and the young of the last brood. Monias stilts form larger groups, the exact composition of which, however, has not yet been researched. Even single-color mesite live in pairs, but rarely lead a cub with her. In the groups, contact between the individuals plays a major role, the birds care for each other's plumage and sleep together. Especially with the short-footed stilt rail it happens time and again that group members argue about larger prey. Groups defend territories that may overlap with those of neighboring groups. When the groups come together, territorial fights can occur, during which the animals chop and kick one after the other and flutter vertically upwards to impress.
Often, stilt claws are accompanied by commensalist species such as the hooded drongo . These species eat the invertebrates that have escaped the stilt claws and occasionally hunt them off for food , which then turns them into food parasites. Other birds regularly hang out near stilt claws, although they do not appear to interact with them. It is assumed that the animals mutually benefit from better monitoring of the environment and thus from better protection against predators .
When threatened by a predator , in the case of stilt claws, especially by Madagascar goshawks and humans , the animals flee into dense vegetation or remain motionless in their location. When they feel threatened, Monias stilt claws occasionally break up the group structure, flee in different directions and finally remain motionless. Another escape tactic is to fly onto a branch and press yourself flat and motionless against the bark. The Madagascar mongooses that live in Madagascar - such as the narrow-striped mongoose and the ring -tailed mongoose - are not viewed as a threat by stilt claws. The birds hardly change their behavior when one of these animals appears and obviously do not belong to their range of prey.
nutrition
Insects are the main food of all types of stilts, seeds and small fruits are only consumed in small quantities and on occasion. Cockroaches , crickets and spiders up to a size of about one centimeter make up the majority of the food of the short-footed stilt rail, the Monias stilt rail also eats grasshoppers , larvae and beetles . Occasionally, the stubby - tailed chameleons of the genus Brookesia, which are just a few centimeters long and live on the ground, are also eaten. While they are eating, the stilt claws walk around slowly, inspecting their surroundings very carefully, turning leaves and branches, searching the low vegetation and pecking at the invertebrates that appear . Dry, curled leaves are picked up with the beak and hit against the ground or branches so that any hidden small animals can come out and be eaten. Monias stilt claws, which have the longest and most curved beak of the three species, often look for their food by probing the foliage layer with their beak or by digging in it in order to feel and catch small animals living underneath. The two species of the genus Mesitornis , which have shorter beaks, always carefully put the branches they have picked up and twisted back to their place of origin after they have been examined, so as not to startle potential prey. If this has happened, however, and a prey animal flees across the ground, the birds run short distances to catch the escaped animal. During the dry season , the short-beaked species also dig in the ground more often. It is not known whether the young birds are fed by their parents or whether they eat independently immediately after leaving the nest. A large part of the water requirement is obviously covered by food, only very rarely do stilts drink small amounts of water.
Reproduction
Species of the genus Mesitornis live in lifelong monogamous partnerships. The Monias stilt claw probably lives polygamously , several females seem to lay eggs in a common nest. So far, courtship behavior has not been proven with certainty, although fights between males of the Monias stilt rail were observed during the breeding season .
The breeding season of all species falls in the rainy season , the eggs are laid between April and October, whereby clutches in September and October are probably second clutches after clutch loss. Nests of the genus Mesitornis are usually one and three meters high in sparse vegetation. The nests of all kinds consist of dry twigs and are padded with leaves and grass. The clutch size ranges from one to three eggs. How many eggs in a clutch come from one female is not clear with Monias stilt claws, since several females can use one nest. The eggs are elliptical in shape and whitish or light yellow in color with red-brown, sometimes gray spots. Although all species are similar in size, the sizes of the eggs differ significantly. The largest species, the Monias stilt claw, lays 37 × 28 mm eggs, while the eggs of the short-footed stilt claw are around 33 × 26 mm. With 44 × 30 mm eggs, the single-color stilt claw lays eggs that are unusually large in relation to their body size. The clutches of short-footed stilts are only incubated by the females, the males only stay nearby, whereas Monias stilts males also breed.
Juveniles are precocial , the exact time when they leave the nest, and the way the chicks get from the nest on the ground, has no information. Males and females take care of the offspring together, which, at least in the case of short-footed stilts, stays with the parents for more than a year. Hence, it is believed that stilt claws do not breed every year.
Various animals, especially snakes and rodents , eat clutches of the stilts. Chicks can fall prey to snakes and larger birds .
Systematics
The systematic classification of the Mesitornithidae is controversial and still the subject of scientific discussion. Since the first description , the stilts have been assigned to the pigeon birds , the chicken birds and the passerine birds one after the other . However, due to their anatomical features, the Mesitornithidae are often viewed as particularly primeval relatives of the railroads , with which they have some similarities, but also have certain differences. In comparison to the rails, the stilts lacks the undivided nostril, and the stilts have 14 control springs , whereas the rails only have twelve. A classification is made more difficult by the fact that no fossil specimens have been found so far . Nevertheless, they are often seen as very original and as different from the other crane birds and therefore placed in the suborder Mesitornithes. In 2004, on the basis of phylogenetic studies, it was proposed that the Mesitornithidae, together with the cuckoo birds, be regarded as a monophyletic taxon in the future . A confirmation of this view remains to be seen. Today the family is put into its own order , the Mesitornithiformes.
The division of the family into the two genera Mesitornis and Monias was based on the differences in the beak and egg shape and the ice structure. In the 19th century and at the beginning of the 20th century, the two species of the genus Mesitornis were regarded as males and females of only one sex-dimorphic species because of their very similar anatomy , an error that was not finally recognized and corrected until the 1930s.
- Genus Mesitornis :
- Short-footed stilt rail , Mesitornis variegata
- Single-color stilt claw , mesitornis unicolor
- Genus Monias :
- Monias stilt claw , Monias benschi
Stilts and people
Stilt claws are well known to the inhabitants of Madagascar and are revered or feared depending on the area. The Monias stilt claw is called Naka . Depending on the region, short- footed stilts are called Agolin'ala or Tolohon'ala . Agolin and Toloho are the names for the Cuvierralle and the Tulukuckuck , ala means forest . The short- footed stilt rail , like some other species of small ground birds, is also known as fangadiovy , the 'yam digger'. The origin of this name is unclear, as stilt claws do not eat and dig up yams . Monochrome stilt claws are called roatelo in the north of their occurrence , which means something like 'two-three' and apparently refers to the group composition of the species that always lives in groups consisting of two parent animals and at most one young animal. In the south, however, it is called Tsikozan'ala , Tsikola is the name for the Cuvierralle in this region, ala also here the name for forest. The local population does not distinguish the monochrome stilt claw by name from the gray-throated claw , although the differences between the animals are known.
The population hunts all three species of the Mesitornithidae sometimes very intensively. Hunters drive the birds in front of them until they are exhausted, shoo them into trees and finally kill them with clubs. Slingshots or bows and, more recently, rifles are also used to kill the birds. With snare traps actually used when hunting larger birds, stilt claws are occasionally also caught. It is noticeable that the best-researched short-footed stilt claws sing significantly less near human settlements and are even more shy than elsewhere, and the population density in these areas is very low. The single-color stilt claw is subject to a "taboo" in the northern and central area of its distribution and is therefore considered inviolable, it is not hunted, and in some cases its name may not even be pronounced. The animals are considered to be extremely human there, as they are said to follow their young to the villages when people have removed the chicks from the nest. In some places, however, the taboo is also based on fear of animals; people fear them for reasons that are not known. This taboo is often only familiar to the locals and is only followed by them. New settlers from areas without taboo or the occurrence of stilts know and usually do not follow it.
Threat and protection
The mesite are one of the most endangered bird families , all kinds are on the IUCN as Vulnerable (Endangered) out. It is feared that the populations of the species will shrink by around 50% in the next 20 years, as the ecosystems of Madagascar are being destroyed at great speed and the species are thus deprived of their habitat . Since the short-toed and Monias stilt rail in particular live in extremely limited areas, they are particularly endangered by clearing , slash and burn , urban sprawl , pollution and hunting . To make matters worse, all species occur in relatively low population densities and can therefore only poorly compensate for losses. Neozoa such as rats that have been introduced to Madagascar can also become a threat because they eat the birds' clutches and thus reduce breeding success. Once a population has died out in an area, it is very difficult or impossible for stilt claws to repopulate this area in the future, even if the necessary habitat should still exist. Due to the poor ability to fly and the low reproduction rate, the stilt claws can only spread very slowly. Forest areas close to the water are of particularly great importance, at least for the short-footed stilt rail, as the species achieves the greatest breeding success in these areas and these areas are therefore important for maintaining the population in much larger areas. If such forests are destroyed, the impact on a subpopulation can be catastrophic. Due to the large-scale settlement of Madagascar, large parts (around 70%) of the original forests in the area where the stilts are distributed have already disappeared. Although there are protected areas , the control of these areas is neglected, so there is hardly any protection. The small distribution area of the Monias stilts does not include a protected area. None of the species are subject to legal protection.
swell
Much of the information in this article is taken from:
- Josep del Hoyo , Andrew Elliot, Jordi Sargatal: Handbook of the birds of the world. Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona 1996, ISBN 84-87334-20-2 .
The following sources are also cited:
- ↑ G. Mayr, PGP Ricson. Evidence for a sister group relationship between the Madagascan mesites (Mesitornithidae) and cuckoos (Cuculidae). Senckenbergiana biologica 2004, 84, pp. 119–135, web link: [1]
- ↑ Bustards, mesites, Kagu, seriemas, flufftails & finfoots in IOC World Bird List
- ↑ BirdLife International (2007): Mesitornithidae , January 10, 2008
Web links
- Stilt claws in the Internet Bird Collection
- Mesitornithidae on the IUCN Red List of Threatened Species 2007. Retrieved January 4, 2008.
