Recurvirostridae

Stilt ( Himantopus himantopus )

The Avocet ( Recurvirostridae ) are a family of the order Charadriiformes ( Charadriiformes ). They are found in almost all tropical and temperate zones of the world. They are characterized by a long neck, long legs and a long, slender beak. This is either straight or shaped, depending on the genus plainly curved upward. The three genera - the actual avocet, stilt and the Schlammstelzer - are outwardly very different, yet closely related.

Features

All species are intrinsically the long beak, a long neck and very long legs. The beak is bent upward at the actual avocets and provided with slats to filter the food. In contrast, stilt have a straight or almost imperceptibly curved beak, which the fins are missing. The Schlammstelzer which mediates in these as in other characteristics between the two genera, has a straight beak like the stilt walkers, however, carries the slats.

The legs of the real avocets are blue gray in color, the pink of the other classes. Actual avocets have three front toes and the hind toe ( anisodaktyler feet). The front toes are connected by basal webbed. In the stilt-walkers, there is no hind toe ( tridaktyler feet) and no webbed feet. Again, give the Schlammstelzer that have a tridaktylen foot with basal webbed.

Typically, the plumage is black and white patterned. In three non-European species comes as a third color or add reddish brown. Only the Black -winged Stilt is solid black in color. The youth dress same as or similar to the appearance of adult birds. An exception is also the Black -winged Stilt, are virtually indistinguishable from the actual stilt in the juvenile birds.

Distribution and habitat

Avocets are found on every continent except Antarctica. They inhabit temperate, subtropical and tropical climates. The preferred habitat is shallow marshland in treeless landscapes. Actual avocets are found primarily in salt lakes and lagoons. The stilt-walkers are more flexible in their choice of habitat and are both rivers to find as lakes, and also to freshwater and in brackish water. Breeding areas are usually inland, outside the breeding season finds Avocet also on the coasts. A particular habitat, the Andensäbelschnäbler, which breeds up to 5000 m in the Andes at altitudes.

With the exception of Andensäbelschnäblers and black stilts rotor are at least sub-populations of migratory birds of all kinds. So drag large parts of the populations of the northern and southern temperate zone in warmer regions. The train usually takes place at night in small groups. The birds follow it coasts or rivers.

Way of life

Avocets are mainly, but not exclusively diurnal. In addition to the day-night rhythm of the tides determine the activity times of the avocet. With the exception of the solitary black stilts rotor, the birds live in small to very large organizations. During the breeding can be found in actual avocets and stilts five to one hundred couples together. When Schlammstelzer the colonies may include many thousands of couples, however. Outside the breeding season live Avocet in larger groups.

Nutrition

The different anatomical structure of beaks due to different diets: The actual avocets and Schlammstelzer put the fins on their beak edges a search for food. With just a little beak open, they make lateral pivotal movement through shallow water or mud. Approximately every two seconds in front of the tongue pushes and pulls off hanging on the blades remained small organisms. In this way, live crustaceans and worms are mainly recorded in the plankton. In addition to this Seihmethode food is ingested directly by pecking. For the stilt walkers, this is almost the only kind of food intake. These are mainly insects and their larvae and worms eaten.

Play a minor role in the diet mollusks, small fish and aquatic plants.

Reproduction

Avocet live in seasonal monogamy, the Black -winged Stilt is lifelong monogamous. They breed in colonies where the nests are five to thirty feet apart; only when Schlammstelzer the nests are much more densely packed within a colony here may lie on a square up to eighteen nests. Often Avocet form mixed colonies with other wading birds.

There are almost always three to four eggs are laid, although extremes of only one egg or eight eggs have become known. The eggs are yellow or brown ( when Schlammstelzer white) with dark spots. The size is 4.5 to 5.5 × 3 to 4 cm. Both partners brood and move frequently from. The defense of the nest is the responsibility of both partners. Potential nest predators are either attacked or lured away from the nest, for example by simulating a wing injury.

The young birds the actual avocet and stilt walkers are beige or brown colored with black patches. They hatch synchronously and leave the nest within the first twenty-four hours. Then they stay for a few months near their parents. An exception here is the Schlammstelzer whose young are solid white and come together after hatching in large " kindergartens ".

Phylogeny

As a phylogenetically very old family avocets are occupied since the early Eocene. Fossil genres of the time are Coltonia (North America), Kashinia ( UK) and Fluviatilavis (Portugal).

System

The Avocet belong to the order Charadriiformes. Within this order are according to DNA analyzes, the next of kin, the oystercatcher, the Ibisbill and parts of the paraphyletic family of plovers.

The three well distinguishable genera and their species are:

• Stilt ( Himantopus ) Stilt ( H. himantopus )
• White face Stilt ( H. leucocephalus)
• American Stilt ( H. mexicanus )
• Collar Stilt ( H. melanurus )
• Black -winged Stilt (H. novaezelandiae )

• Schlammstelzer (C. leucocephalus)

• Avocet (R. avosetta )
• American Avocet or Braunhalssäbelschnäbler (R. americana)
• Rotkopfsäbelschnäbler (R. novaehollandiae )
• Andensäbelschnäbler (R. andina )

The number of species within the genus Himantopus is controversial. Some authors see from the listing shown above, only the Black -winged Stilt, as an independently and take the others as subspecies of the same species on. In addition to these, there are still some authors in the Hawaiian stilt ( H. knudseni ). Since the Black -winged Stilt hybridized with the white face - stilt, even the elimination of the black stilt runner is questionable.

The relationship of the three genera to each other is unclear. Studies brought contradictory results which indicate that sometimes the genus Himantopus was found as a sister group of the other two, then the genus Cladorhynchus as a sister group of the other.

People and avocets

The actual Avocet was once almost extinct in Central and Western Europe. His re-entry into the UK after a hundred years of absence in 1941 was a success story of the Royal Society for the Protection of Birds, the one avocet leads in the logo today. Since today play the exploitation of avocets as edible birds and sport hunting does not matter anymore, destruction of wetland habitats has become a greater threat.

At the species level, only one species is endangered: The Black Stilt is performed threatened by the IUCN status of extinction. After he was often in the 19th century, there was a dramatic decline in the 20th century, which was brought about mainly by the new arrivals in New Zealand cats, weasels and rats as well as by the frequent hybridizing with the white face stilt. In 2001 there were only seven breeding pairs. This number was increased to twenty now back, but this constant release of captive reared animals is necessary.