Plover

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Plover
Kentish plover (Western Snowy Plover; Charadrius alexandrinus nivosus)

Kentish plover (Western Snowy Plover; Charadrius alexandrinus nivosus )

Systematics
Sub-stem : Vertebrates (vertebrata)
Class : Birds (aves)
Order : Plover-like (Charadriiformes)
Family : Plover
Scientific name
Charadriidae
Vigors , 1825

The plovers (Charadriidae) are a family of birds from the order of the plover-like (Charadriiformes). The members of the worldwide spread family are small to medium-sized waders , whose legs are usually relatively short or at most medium-long. This family is characterized by a short beak and, in many species, a compact, rounded body. Most species live in open landscapes near bodies of water and feed on invertebrates . The IUCN lists seven of the approximately 70 species as “ endangered ”, “ critically endangered ” or “ critically endangered ”.

features

anatomy

Although the plovers are a species-rich family, their physique is fairly uniform. The largest species are only about twice as large as the smallest species: The smallest plover is the Azararegenpfeifer with a head-body length of 15 centimeters and weighing 30 grams, the heaviest member of the family is the masked lapwing , a head Hull length of 35 centimeters and a weight of 370 grams reached.

Little ringed plover in flight

Characteristic of all plovers are the relatively large eyes, the iris of which is brightly colored in many species. A large number of eye rods on the retina enables plovers to see even in low light conditions. The head appears rounded and sits on a rather short neck. The birds often have their necks drawn in, which is why the body of many species appears globally as a whole. With a few exceptions, the thin legs are short or at most medium-long in relation to the body, the rear toe is very short and in many species only rudimentary . As with all taxa of the suborder Charadrii, the toes are not webbed together.

The beak is straight, usually relatively short and has a blunt tip. It is never longer than the distance between the base of the beak and the rear edge of the eye. A special feature is the beak of the New Zealand crooked beak , the tip of which is bent to the right. In most species, the beak is slightly thicker at the tip than in the middle and carries numerous pressure-sensitive receptors, the so-called Herbst's corpuscles . These are used to track down and examine possible prey in the substrate .

Salt glands are located between the eyes and secrete salt from the blood plasma directly into the nasal cavity .

The species of the genus Vanellus differ from the other plovers in some morphological peculiarities: They wear feather bonnets , have skin flaps on their faces or they have horny thorns on their carpal bones . A combination of these features also occurs. Usually the characteristics are more developed in males than in females. Many of these species are characterized by their broad, rounded wings. Most other plovers have long, rather narrow wings that allow them to fly quickly.

Coloration and plumage

Portrait of a red-raped lapwing

The plover's plumage is usually colored in a combination of gray and brown tones as well as black and white. Many species have banded markings on the chest and head. Smaller species in particular often show a camouflage pattern of spots and stripes, larger species are often more conspicuously colored, especially the skin flaps on the face of some members of the Vanellus genus are conspicuously colored. In many species, the males are more intensely colored than the females. In this regard, only the Mornell Ringed Plover is an exception: in this species, the female is much more intensely colored than the male during the breeding season. Species that live in colder areas and overwinter have significantly more down and cover feathers than adapt to the cold temperatures in their habitat .

Many plovers are more intensely colored during the breeding season than during the rest of the year, but the difference between simple and beautiful dress is usually relatively small. Shortly before the breeding season, plovers renew the cover plumage on the breast and forehead so that this plumage is most intensely colored during courtship . These feathers fade within a few weeks, so that the birds are clearly better camouflaged again during the breeding business. The rest of the head plumage is moulted when the clutch is incubated. The main moult , during which all other feathers are exchanged, takes place after the breeding season. The ability to fly is retained because all springs are never replaced at the same time. The entire moult takes a period of three to five months.

voice

The different genera of the plover sometimes differ very clearly in terms of their vocalizations. Most of the smaller species, such as those of the genus Charadrius , call rather softly and almost exclusively in the breeding area; in case of danger they also utter soft, high-pitched calls. Larger plovers like lapwing, on the other hand, usually call more frequently, louder and more piercing than their smaller relatives. It is known that most species can handle a multitude of different calls of different volume, modulation and length. Apart from the various warning calls that give precise information about the type of potential danger, the vocalizations of plovers have only been little researched. Some species use spectacular singing flights for courtship, during which they sometimes whistle long, melodious stanzas, various short sounds are used to communicate with conspecifics and young birds.

distribution and habitat

Distribution of the plover

Plover can be found on all continents and in all climatic zones of the earth. They usually colonize open habitats near bodies of water, especially marshland , grassland and tundra near the coast, but also inland up to the mountains . Few species live in extremely dry areas. Migrating species sometimes change habitats several times a year in the course of their migration. The plovers reach the greatest number of species in the lower latitudes of the southern hemisphere.

Way of life

Migratory behavior

Within the plover there are long-distance migrants and short-range migrants as well as species that are faithful to their location . Most migratory species belong to the subfamily Charadriinae, while there are few migratory birds within the subfamily Vanellinae. Most of the migrating species come together in groups of up to a few hundred individuals before the migration begins, only a few species migrate alone. It is also common for migrating plover to team up with other migrating waders and fly with them in a group. The migration behavior is often strongly synchronized, a large part of a local population moves to winter quarters and back at the same time. During longer flights, the groups are structured and often fly in formations.

Like all migratory birds, the long-distance migrants among the plovers in particular ingest a lot of food before the start of the migration, which increases their body mass by up to 50 percent. The eaten fat is stored under the skin all over the body. In addition, in the preparation phase for the train, the digestive organs enlarge and the flight muscles show hypertrophy immediately before departure . The greatest distances are covered by some species of the genus Charadrius , which switch between wintering sites in tropical Africa and breeding sites in the boreal and arctic climatic zones, covering a few thousand kilometers. Some species that live all year round in the tropics and subtropics move short distances to the next larger water reservoirs when the dry season begins.

Activity and comfort behavior

During the course of the day, many species migrate short distances between their roosts and the feeding grounds in bodies of water. Species that live on coasts also migrate with the waterline when the tide rises or falls , in order to look for food there. Species widespread in the tropics and subtropics often retreat to the shade of higher vegetation in the hot midday hours.

In addition to fluffing up their plumage and occasional bathing, plovers show the comfort behavior of stretching wings and legs, which is typical for many birds. A wing and the leg on the same side of the body are spread apart and stretched from the body at the same time. Species with distribution areas in cooler climates take sunbaths when the sun is shining by spreading their wings slightly and facing the sun.

Social and antagonistic behavior

Plovers defend a territory during the breeding season, even if they breed in loose colonies . However, many species find themselves together in sometimes larger, loose groups to forage both during and outside the breeding season.

The breeding ground is mainly defended by the males. If there are disputes on the territorial border, the two opponents threaten each other by standing in front of each other, slightly fluffed up and showing their mostly strongly colored breast and face plumage. The iris , which is brightly colored in some species, also plays a role in these threatening rituals. The eye is opened wide while the pupil is narrowed, making the iris appear larger.

Outside of the breeding season, some species defend small feeding grounds, which are, however, not as sharply demarcated as the breeding grounds. The defense of these areas takes place by means of ritualized threatening gestures, which differ from those used to defend a breeding area. The opponents run towards each other with bowed heads and fanned tail feathers and then run side by side with slightly spread wings. The plumage on the back is fluffed up slightly, the tail plumage remains fanned out. Occasionally this behavior is interrupted by the two birds standing upright in front of each other and spreading the wing facing the opposite downwards.

When plovers feel threatened, they usually try to get to safety on an ongoing basis. Species camouflaged by their plumage often also press flat on the ground. As soon as they feel posed, plovers fly up and try to reach the closest cover. Plovers that appear in flocks are more likely to fly up than individual birds, which can more easily become prey for predators without the flock's protection.

During the breeding season, many species mislead potential nest and brood predators by simulating an injury and trying to lure the predator away from the nest. As soon as the young birds have hatched, plovers also try to scare away the predator by fluttering around in front of him, shouting loudly and poking at him from the air.

Thanks to their good eyesight, plovers can recognize dangers from a great distance. Most species have developed warning sounds for various hazards. They warn against birds of prey with a different call than against predators living on the ground. They also differentiate between nest predators and, in this regard, harmless species.

nutrition

Ringed plover with a captured crab

All plovers feed mainly on invertebrates , but seeds and fruits are also ingested in very small quantities, if these are available.

Plovers rely on sight to hunt; so they wait until a prey shows up. Many species forage for food both during the day and at dusk and occasionally at night. To catch prey, they search large, open areas or flat vegetation. When foraging for food, many species show characteristic behavior: they run short distances and then pause for a moment. The breaks serve to visually search the surrounding area for potential prey, which can then be reached with another sprint. Species of the genus Charadrius in particular show this behavior particularly frequently. Plover can also startle or lure prey by tripping their legs quickly on the ground while standing in place. This is how small animals are scared off. Other prey that live in the ground come to the surface, mistaking the knocking sound for rain or a burrowing predator. In addition to these behaviors, the foraging for food is also carried out by the birds running around slowly and with lowered eyes to discover prey or by probing the uppermost substrate layer with their touch-sensitive beak. An exception to the search for food is the crooked beak, which gropes for small animals under stones with its eponymous, curved beak.

Plovers avoid looking for food in the immediate vicinity of the common snipe birds, which often occur in the same habitat. With their longer beaks, these probes deeper, soft subsoil, while the plovers generally use harder, less deep substrates. This is an example of the no-competition principle .

Most species never or very rarely drink and ingest all of the water they need with their food. When they drink, the beak is filled with water and the head is thrown up to swallow the water as they are unable to suck the water into the beak.

Reproduction

Pair formation

Courting wedge-tailed plover

Most species of plover do not breed until they are two years old, and annuals only breed in exceptional cases. At the beginning of the breeding season, the males begin to defend a breeding territory and courtship . In most species, courtship consists of ritualized movements that the male performs while approaching a female. The courtship usually includes the presentation of the conspicuously colored plumage on the head and chest, while the courting bird paces up and down in front of the courted partner and makes soft, chuckling sounds. Often the wings and tail plumage are spread out in the direction of the female. With some species, the courtship is accompanied by sometimes acrobatic flights and singing. Few species show a reversal of roles between the sexes: the females court and defend territories, while the males mainly take care of the clutch.

Nest building and nest location

Clutch of a lapwing

Plovers are without exception ground- nesting birds that usually create their nests between or under low vegetation or between stones. The nest of most species consists only of a hollow, which is only sparsely padded with plant material and feathers, but the eggs are often laid directly on the ground. Few species gather material to build a flat hill with a nesting trough.

Clutch and brood

Depending on the distribution, plovers breed in summer or shortly after the rainy season when the food supply is greatest. Most species raise only one brood per year, but if the first brood is lost prematurely, most species lay new eggs . Many species occupy their breeding grounds long before the start of breeding. There are persistently monogamous as well as polygamous and polyandric types. In polygamous and polyandric species, a partner often leaves the brood shortly after the eggs have been laid and looks for a new partner to start another brood.

Red-headed plover a few hours old chick
One day old plover chick of the wedge-tailed plover

The two to four pear-shaped eggs in a clutch are usually laid one to two days apart. In most species, an egg has a mass that corresponds to 20 to 30 percent of the body mass of the female. The eggs of plovers have a light basic color, which is mostly creamy white, beige or greenish, and have dark spots of different sizes. Except in the case of distinctly polygamous species, in most species both parent animals take on equal parts warming of the eggs. Species that breed in warm climates ensure that the clutch is adequately cooled by soaking their belly and breast feathers with water and then sitting on the clutch. The eggs are then cooled as the water evaporates.

The young birds hatch at a maximum of two days after a breeding period of 21 to 30 days; the breeding period of the smaller species of the family is usually in the lower range of this spectrum. Immediately after hatching, the parent animals carry the eggshells out of the nest and place them at a distance, some species even hide them. This behavior prevents the white glowing inside of the shells from attracting nest predators. The chicks are highly capable of fleeing the nest and are able to look for food outside the nest immediately after hatching, regardless of their parents. After a short time, however, they return to the nest or are fetched back by the parent animals to be warmed. At the time of hatching, the chicks already have very strong legs and feet and a large head and wear a dense down dress, which is usually beige to brown in color. In many species, this down dress has a camouflage pattern made up of dark dots and stripes. As soon as all the chicks have hatched, the parents leave the nest with them and run towards the nearest watering hole, moving as far as possible through dense vegetation to protect them from predators. During the first two to three weeks, the parent animals warm the chicks regularly, as they cannot maintain their body temperature on their own during this time. The young birds fledge after three to four weeks, up to this point in time an average of 25 to 30 percent of the young birds survive.

Systematics

Tribal history

The modern plover probably originated around 40 million years ago in the late Eocene . The first fossils that can be safely assigned to plovers come from the 30 million year old Oligocene of Colorado and from Belgium . Due to the similarity of the plover to a variety of bird families, the theory was that after the mass extinction at the Cretaceous-Tertiary boundary 65 million years ago some plover similar taxa could have survived that make up the sequence by adaptive radiation , the recent Neornithes have formed . Molecular genetic studies, however, suggest an older origin for modern birds is more likely.

External system

Plover together with the snipe birds make up a large part of the plover-like species . The strong ecological and morphological similarity to the snipe birds earlier justified the assumption that these two families are closely related. In the 19th and 20th centuries it was assumed that the two groups form sister taxa within the order of the Charadriiformes. Today, however, both families are assigned to the plover species in different subordinates, the plover to the Charadrii and the snipe bird to the Scolopaci. Within the Charadrii, the plover are most closely related to the avocets (Recurvirostridae), the oystercatchers (Haematopodidae) and the ibis beak (Ibidorhynchidae). The Magellanic Plover was placed among the Charadriidae for a long time, but morphological, behavioral and genetic studies came to the conclusion that it should be placed in a family of its own that is not closely related to the plovers.

Internal system

Bronze lapwing ( Vanellus chilensis )

The plovers are traditionally divided into two subfamilies , the lapwing (Vanellinae) , which occurs mainly in Africa, and the plover (Charadriinae). The position of the genus Pluvialis , which was traditionally placed in the plover family, is controversial . According to some genetic studies, pluvialis is not closely related to the other genera of the plover. According to a more recent study, in which more DNA sections were compared with one another than in the earlier studies, Pluvialis is part of the plover, basal as a sister group of all other plover genera. Winkler and colleagues therefore place the genus Pluvialis in an independent subfamily.

Plover and human

The Australian masked plover is threatened by increasing habitat loss.

Plover were and are hunted for their meat and their eggs collected. Some species are well known in their area of ​​distribution and have become part of the local culture partly because of their traditional use as food and partly because of their appearance, which many people consider cute . Egg collecting and plover hunting are often traditional events. Some species of the genus Vanellus are kept as pets and used to guard properties. Due to their great attention, they recognize intruders very early and report them loudly.

Some species are cultural followers that can only colonize certain areas through human activities. Especially in Asia and Africa, where large areas along the coasts are cleared, grassland, pasture areas and less intensively used fields are created that are used by plovers.

Many species are threatened by increasing loss of their habitat. Drainage, increased grazing and intensification of agriculture are destroying the breeding, resting and wintering areas of many species worldwide. In addition, excessive egg gathering and hunting pose a threat to some species. Species with a small range and endemics on islands are particularly threatened . Introduced rats and domestic cats destroy clutches and eat chicks and breeding birds.

supporting documents

Web links

Commons : Plover  - Album with pictures, videos and audio files
Wiktionary: plover  - explanations of meanings, word origins, synonyms, translations

swell

Much of the information in this article is taken from:

In addition, the following sources were used:

  1. ↑ Charadriidae in the IUCN Red List of Threatened Species 2010. Accessed on 03.03.2011.
  2. ^ SL Olson: Aspects of the global avifaunal dynamics during the Cenozoic. In: Proceedings of the 19th International Ornithological Congress. University of Ottawa Press, 1989, pp. 2023 ff.
  3. ↑ A. Feduccia: Explosive evolution in tertiary birds and mammals. In: Science. Volume 267, No. 5198, 1995, pp. 637-638.
  4. ↑ J. Cracraft: Avian evolution, Gondwana biogeography and the Cretacious-Tertiary mass extinction event. In: Proceeding of the Royal Society B. Volume 268, No. 1466, 2001, pp. 459-469.
  5. ↑ a b David W. Winkler, Shawn M. Billerman, Irby J. Lovette: Bird Families of the World: A Guide to the Spectacular Diversity of Birds. Lynx Edicions, 2015, ISBN 978-84-941892-0-3 , pp. 130-131.
  6. ↑ a b A. J. Baker, SL Pereira, TA Paton: Phylogenetic relationships and divergence times of Charadriiformes genera: Multigene evidence for he Cretaceous origin of at least 14 clades of shorebirds. In: Biology Letters. Volume 3, No. 2, 2007, pp. 205-209.
  7. ^ TA Paton, AJ Baker, JG Groth, GF Barrowclough: RAG-1 sequences resolve phylogenetic relationships within Charadriiform birds. In: Molecular Phylogenetics and Evolution. Volume 29, No. 3, 2003, pp. 268-278.
  8. ↑ Per GP Ericson, I. Envall, M. Irestedt, JA Norman: Inter-familial relationships of the shorebirds (Aves: Charadriiformes) based on nuclear DNA sequence data. In: BMC Evolutionary Biology. Volume 3, No. 16, 2003, doi: 10.1186 / 1471-2148-3-1 .
  9. ↑ Allan J. Baker, Yuri Yatsenko, Erika Sendra Tavares: Eight independent nuclear genes support monophyly of the plovers: The role of mutational variance in gene trees. In: Phylogenetics and Evolution. Volume 6, No. 2, November 2012, pp. 631-641, doi: 10.1016 / j.ympev.2012.07.018 .

Literature in German