Hybridisation in shorebirds has been proven on only a small number of occasions; however, many individual shorebirds have been recorded by birdwatchers worldwide that do not fit the characters of known species. Many of these have been suspected of being hybrids. In several cases, shorebird hybrids have been described as new species before their hybrid origin was discovered. Compared to other groups of birds (such as gulls), only a few species of shorebirds are known or suspected to hybridize, but nonetheless, these hybrids occur quite frequently in some cases.
An apparently new sandpiper species ("Cooper's sandpiper Tringa/Calidris cooperi") was described in 1858 based on a specimen collected in 1833 on Long Island, New York. A similar bird was collected in 1981 at Stockton, New South Wales, Australia. These are probably hybrids between the curlew sandpiper ("Calidris" ferruginea) and the sharp-tailed sandpiper (Philomachus acuminatus/Calidris acuminata).
Cox's sandpiper ("Calidris" × paramelanotos), described as a new species in 1982, is now known to be a stereotyped hybrid between males of the pectoral sandpiper ("Calidris" melanotos) and female curlew sandpipers. It is known from nearly two dozen sightings since the 1950s, almost all of which are from Australia, with one record from Massachusetts. and another from Japan.
A stint at Groote Keeten in the Netherlands which was initially thought to be that country's first record of the least sandpiper but which showed anomalous features, was postulated to be a hybrid between little stint ("Calidris" minuta) and Temminck's stint ("Calidris" temminckii).
Putative hybrids between the dunlin ("Calidris" alpina) and the white-rumped sandpiper ("Calidris" fuscicollis) have been occasionally seen in northeastern North America. In Europe, on the other hand, an apparent hybrid between the dunlin and the purple sandpiper ("Calidris" maritima) has turned up.
Occurrence of intrageneric hybridization has been reported between the buff-breasted sandpiper ("Tryngites" subruficollis) and the white-rumped (or possibly Baird's, "Calidris" bairdii) sandpiper – the parent species apparently do belong into the same genus, however (see calidrid) -, as well as between the common and the green sandpiper (Tringa ochropus).
The "avistilt" or "stavocet" is a hybrid between black-necked stilt (Himantopus mexicanus) and American avocet (Recurvirostra americana), occasionally found in California. One such bird was accidentally bred in the San Francisco Zoo in 1971 and lived at least until 1974. The avocet was the father and the stilt the mother of this individual, which apparently was a male.
A bird hybrid is a bird that has two different species as parents. The resulting bird can present with any combination of characters from the parent species, from totally identical to completely different. Usually, the bird hybrid shows intermediate characteristics between the two species. A "successful" hybrid is one demonstrated to produce fertile offspring. According to the most recent estimates, about 16% of all wild bird species species have been known to hybridize with one another; this number increases to 22% when captive hybrids are taken into account. Several bird species hybridize with multiple other species. For example, the Mallard (Anas platyrhonchos) is known to interbreed with at least 40 different species. The ecological and evolutionary consequences of multispecies hybridization remain to be determined.In the wild, some of the most frequently reported hybrids are waterfowl, gulls, hummingbirds, and birds-of-paradise. Mallards, whether of wild or domestic origin, hybridize with other ducks so often that multiple duck species are at risk of extinction because of it. In gulls, Western x Glaucous-winged Gulls (known as "Olympic Gulls") are particularly common; these hybrids are fertile and may be more evolutionarily fit than either parent species. At least twenty different hummingbird hybrid combinations have been reported, and intergeneric hybrids are not uncommon within the family.Wood-warblers are known to hybridize as well, and an unusual three-species warbler hybrid was discovered in May 2018. Hybridisation in shorebirds is unusual but reliably recorded.Numerous gamebird, domestic fowl and duck hybrids are known. Captive songbird hybrids are sometimes called mules.The scientific literature on hybridization in birds has been collected at the Avian Hybrids Project.Calidrid
The calidrids or typical waders are a group of Arctic-breeding, strongly migratory wading birds. These birds form huge mixed flocks on coasts and estuaries in winter. They are the typical "sandpipers", small to medium-sized, long-winged and relatively short-billed.
Their bills have sensitive tips which contain numerous Corpuscles of Herbst, enabling the birds to locate buried prey items, which they typically seek with restless running and probing.As some calidrids share the common name "sandpiper" with more distantly related birds such as the Actitis species, the term stint is preferred in Britain for the smaller species of this group.Cox's sandpiper
Cox's sandpiper (Calidris × paramelanotos) is a hybrid between a male pectoral sandpiper (Calidris melanotos) and a female curlew sandpiper (Calidris ferruginea). First discovered in Australia in the 1950s, it was originally described as a species new to science and named after Australian ornithologist John B. Cox. However, it was later found to be a hybrid. Most if not all birds found to date are males, in accord with Haldane's rule.Hybridisation in gulls
Hybridisation in gulls occurs quite frequently, although to varying degrees depending on the species involved.Stint
A stint is one of several very small waders in the paraphyletic "Calidris" assemblage – often separated in Erolia – which in North America are known as peeps. They are scolopacid waders much similar in ecomorphology to their distant relatives, the charadriid plovers.
Some of these birds are difficult to identify because of the similarity between species, and various breeding, non-breeding, juvenile, and moulting plumages. In addition, some plovers are also similarly patterned, especially in winter. With a few exceptions, stints usually have a fairly stereotypical color pattern, being brownish above and lighter – usually white – on much of the underside. They often have a lighter supercilium above brownish cheeks.Terek sandpiper
The Terek sandpiper (Xenus cinereus) is a small migratory Palearctic wader species, the only member of the genus Xenus. It is named after the Terek River which flows into the west of the Caspian Sea, as it was first observed around this area. The genus name Xenus is from Ancient Greek xenos stranger, and cinereus is Latin for "ash-grey" from cinis, cineris, "ashes".Tringa
Tringa is a genus of waders, containing the shanks and tattlers. The genus name Tringa is the New Latin name given to the green sandpiper by Aldrovandus in 1599 based on Ancient Greek trungas, a thrush-sized, white-rumped, tail-bobbing wading bird mentioned by Aristotle.They are mainly freshwater birds, often with brightly coloured legs as reflected in the English names of six species, as well as the specific names of two of these and the green sandpiper. They are typically associated with northern hemisphere temperate regions for breeding. Some of this group—notably the green sandpiper—nest in trees, using the old nests of other birds, usually thrushes.
The willet and the tattlers have been found to belong in Tringa; these genus changes were formally adopted by the American Ornithologists' Union in 2006.The present genus in the old, more limited sense was even further subdivided into Tringa proper and Totanus, either as subgenera or as full genera. The available DNA sequence data suggests however that neither of these is monophyletic and that the latter simply lumps together a number of more of less closely related apomorphic species. Therefore it seems unwarranted to recognize Totanus even as a subgenus for the time being.Wader
Waders are birds commonly found along shorelines and mudflats that wade in order to forage for food (such as insects or crustaceans) in the mud or sand. They are called shorebirds in North America, where the term "wader" is used to refer to long-legged wading birds such as storks and herons. Waders are members of the order Charadriiformes, which includes gulls, auks and their allies.
There are about 210 species of wader, most of which live in wetland or coastal environments. Many species of Arctic and temperate regions are strongly migratory, but tropical birds are often resident, or move only in response to rainfall patterns. Some of the Arctic species, such as the little stint, are amongst the longest distance migrants, spending the non-breeding season in the southern hemisphere.
Many of the smaller species found in coastal habitats, particularly but not exclusively the calidrids, are often named as "sandpipers", but this term does not have a strict meaning, since the upland sandpiper is a grassland species.
The smallest member of this group is the least sandpiper, small adults of which can weigh as little as 15.5 grams and measure just over 13 cm (5.1 in). The largest species is believed to be the Far Eastern curlew, at about 63 cm (25 in) and 860 grams (1.90 pounds), although the beach thick-knee is the heaviest at about 1 kg (2.2 lb).
In the Sibley-Ahlquist taxonomy, waders and many other groups are subsumed into a greatly enlarged Ciconiiformes order. However, the classification of the Charadriiformes is one of the weakest points of the Sibley-Ahlquist taxonomy, as DNA–DNA hybridization has turned out to be incapable of properly resolving the interrelationships of the group. Formerly, the waders were united in a single suborder Charadrii, but this has turned out to be a "wastebasket taxon", uniting no less than four charadriiform lineages in a paraphyletic assemblage. However, it indicated that the plains wanderer actually belonged into one of them. Following recent studies (Ericson et al., 2003; Paton et al., 2003; Thomas et al., 2004a, b; van Tuinen et al., 2004; Paton & Baker, 2006), the waders may be more accurately subdivided as follows:
Family Scolopacidae: snipe, sandpipers, phalaropes, and allies
Family Rostratulidae: painted snipe
Family Jacanidae: jacanas
Family Thinocoridae: seedsnipe
Family Pedionomidae: plains wanderer
Family Burhinidae: thick-knees
Family Chionididae: sheathbills
Family Pluvianellidae: Magellanic plover
Family Ibidorhynchidae: ibisbill
Family Recurvirostridae: avocets and stilts
Family Haematopodidae: oystercatchers
Family Charadriidae: plovers and lapwingsIn keeping more in line with the traditional grouping, the Thinocori could be included in the Scolopaci, and the Chionidi in the Charadrii. However, the increasing knowledge about the early evolutionary history of modern birds suggests that the assumption of Paton et al. (2003) and Thomas et al. (2004b) of 4 distinct "wader" lineages (= suborders) already being present around the Cretaceous–Paleogene boundary is correct.