Belongs within: Charadriiformes.
The Recurvirostridae are a small family of wading birds with relatively long legs, necks and bills, and usually contrasting black and white or red, black and white plumage. One species, the New Zealand Himantopus novaezelandiae, is entirely black. Recurvirostrids are characterised by having the tarsus at least twice the length of, and the naked portion of the thigh much longer than, the middle toe. Three modern genera are included in the family: Recurvirostra, the avocets, have the bills turned up at the end whereas the two genera of stilts, the cosmopolitan Himantopus and the Australian Cladorhynchus, have straight bills. Recurvirostra and Cladorhynchus have more extensive webbing on the feet than Himantopus.
The long legs and bills of recurvirostrids allow them to feed on small aquatic invertebrates by wading in up to their belly. Avocets tend to feed in a sweeping fashion, scything their beak side to side within the water column.
The American avocet R. americana of North America and the red-necked avocet R. novaehollandiae of Australia both have a reddish head and neck.
Stilts and avocets
Published 20 August 2019
Visit a healthy wetland in many parts of the world and you may be able to see boldly patterned, lightly built birds with remarkably long legs and bills wading through the shallows. These are the members of the Recurvirostridae, commonly known as the stilts and avocets.
About a dozen species of recurvirostrid are currently recognised, depending on the exact classification scheme in play. They are divided between three genera with the avocets forming the genus Recurvirostra and the stilts divided between Himantopus and Cladorhynchus. The most obvious distinction between the two subgroups is in the shape of the bill: that of stilts is straight but avocets have a distinct upwards curve towards the end of theirs. A fourth genus has often been included in the Recurvirostridae for the ibisbill Ibidorhyncha struthersii, a striking-looking inhabitant of the upland rivers of the Himalayan plateau, but uncertainty about this bird’s phylogenetic position has led most recent authors to exclude it from the family.
The recurvirostrids feed mostly on small aquatic invertebrates such as brine shrimp or insect larvae. Their long legs, among the longest relative to body size of any bird, allow them to wade in deeply in search of prey. Stilts actively probe the waters and underlying sediment whereas avocets tend to forage by sweeping their bill through the water side to side. Avocets and the banded stilt Cladorhynchus leucocephalus of Australia prefer brackish waters such as lagoons and estuaries, with the banded stilt congegrating around the great salt lakes of inland Australia. Breeding is conducted by monogamous pairs that share the duty of incubating their simple nest on the ground near water. These nests may be gathered into loose colonies; the banded stilt forms particularly large colonies in which the chicks are herded into communal creches of several hundred.
The majority of recurvirostrids are patterned with black or dark brown and white. The red-necked avocet Recurvirostra novaehollandiae has the head and neck coloured reddish-brown as does the American avocet R. americana during the breeding season. The banded stilt has a broad reddish-brown band across the top of the breast. There is also the black stilt Himantopus novaezelandiae of New Zealand, which is somewhat self-explanatory. Beaks are black in all species; the legs are grey in avocets and red in stilts.
Four geographically distinct species of avocet occupy the modern world: the American avocet in North America, the red-necked avocet in Australia, the pied avocet Recurvirostra avosetta in Eurasia and Africa, and the Andean avocet R. andina in South America. The Andean avocet is a bird of high altitudes, occupying shallow, alkaline lakes in the upper Andes. Cladorhynchus includes only the banded stilt. The most varied taxonomy concerns the genus Himantopus. Historically, all the black-and-white stilts (and sometimes also the black stilt) have been recognised as a single near-cosmopolitan species. In more recent years, the trend has been towards recognition of five or six distinct species in the genus. Most of these species are well separated geographically except for in New Zealand where the black stilt shares its range with the pied stilt Himantopus leucocephalus, a more recent immigrant from Australia. The breeding range of the black stilt is currently restricted to a relatively small area of New Zealand’s South Island, and the species is considered endangered due to factors such as habitat alteration and the threat of hybridisation with the more abundant pied stilt*.
*It’s worth spending some thought on the role of hybridisation as a conservation risk. Some observers may express concern that regarding hybridisation as a threat per se carries uncomfortable intonations of “racial purity”, and that limiting the available gene pool may do more harm than good. After all, it’s not as if the black stilt heritage of hybrid individuals is just gone (hybrids between the two species are, I believe, fully fertile and able to produce offspring of their own). The question is, I suppose, do the black stilt genes actually persist in the mixed population? Or does selection and/or drift winnow them out over time? This would be a difficult question to answer, and not without risk to find out.
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Phylogenetically, it is reasonably well established that recurvirostrids form a clade with the ibisbill and oystercatchers. This clade is in turn closely related to the plovers of the Charadriidae; indeed, many recent phylogenies have indicated that the recurvirostrid-oystercatcher clade may even be nested within the plovers as generally recognised. Considering the relatively small number of species in each clade, it might seem reasonable to suggest the recurvirostrids be reduced to a subfamily of the Charadriidae, but bird taxonomists being bird taxonomists, there seems to be more of a push to divide the Charadriidae up instead.
The fossil record of the Recurvirostridae is limited. A handful of species have been assigned to this family from the Eocene, but all are known from limited remains and their position is questionable. Coltonia recurvirostra is known from part of a wing from Utah; it was a relatively large bird, appearing to be more than one-and-a-half times the size of any living recurvirostrid. Fluviatilavis antunesi was described from a femur, humerus and radius from Portugal but was described as exhibiting some primitive features not found in modern recurvirostrids. It is also worth noting that its original description (Harrison 1983) compared it most favourably with the ibisbill, so if that species is not to be regarded as a recurvirostrid, probably neither is Fluviatilavis.
Systematics of Recurvirostridae
<==Recurvirostridae [Avocettidae, Recurvirostrinae]
| i. s.: Coltonia recurvirostraFP64
| Fluviatilavis Harrison 1983U93, M02
| `--*F. antunesi Harrison 1983M02
|--Recurvirostra Linnaeus 1758JT12, CC10 [=Avocetta Brisson 1760CC10]
| | i. s.: R. novaehollandiae Vieillot 1816 (see below for synonymy)CC10
| | R. sanctanebulae Mourer-Chauviré 1978M09
| |--*R. avosetta Linnaeus 1758CC10, JT12, PB96 [=*Avocetta avosettaCC10]
| `--+--R. americana Gmelin 1788JT12, S05 [=Himantopus americanaS05]
| `--R. andinaJT12
`--HimantopodinaeLZ07
|--Cladorhynchus [Cladorhynchini]JT12
| |--C. leucocephalus (Vieillot 1816) (see below for synonymy)WS48
| `--C. pectoralisN87
`--Himantopus Brisson 1760JT12, CC10 [=Hypsibates Nitzsch in Ersch & Gruber 1827CC10; Himantopodidae, Himantopodini]
| i. s.: H. chettusiaD56
| H. melanopterusB42
| H. melanurusRN72
| H. nigricollisSS66
|--H. novaezelandiae Gould 1841JT12, CC10 (see below for synonymy)
`--+--H. mexicanusJT12 [=H. himantopus mexicanusRN72]
`--+--*H. himantopus (Linnaeus 1758)CC10, JT12, CC10 (see below for synonymy)
| |--H. h. himantopusUSDI77
| `--H. h. knudseniUSDI77
`--H. leucocephalus Gould 1837JT12, CC10 (see below for synonymy)
Nomen nudum: Himantopus brevipes Milne-Edwards 1871M02
Cladorhynchus leucocephalus (Vieillot 1816) [=Recurvirostra leucocephala; incl. C. leucocephalus rottnesti Mathews 1912]WS48
*Himantopus himantopus (Linnaeus 1758)CC10, JT12, CC10 [=Charadrius himantopusCC10, *Hypsibates himantopusCC10; incl. H. ceylonensisSU93]
Himantopus leucocephalus Gould 1837JT12, CC10 [=Hi. himantopus leucocephalusCC10; incl. Hi. albicollis Buller 1875 non Vieillot 1817CC10, Hi. albus Ellman 1861CC10, Hypsibates leucocephalus albusCC10, Hy. leucocephalus assimilis Mathews 1912WS48, Hi. picatus Ellman 1861CC10, Hi. seebohmi picataCC10]
Himantopus novaezelandiae Gould 1841JT12, CC10 [=Hi. himantopus novaezelandiaeCC10, Hi. novaezealandiaeCC10, Hypsibates novaezealandiaeCC10; incl. Hi. melas Hombron & Jacquinot 1841CC10, Hi. niger Ellman 1861CC10, Hi. spicatus Potts 1873CC10]
Recurvirostra novaehollandiae Vieillot 1816 [=Recurvirostris (l. c.) novaehollandiae; incl. Avocetta novaezealandiae Ellman 1861, R. rubricollis Temminck 1823]CC10
*Type species of generic name indicated
References
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[U93] Unwin, D. M. 1993. Aves. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 717–737. Chapman & Hall: London.
[USDI77] United States Department of the Interior. 1977. Endangered and threatened wildlife and plants—republication of list of species. Federal Register 42: 36420–36431.
[WS48] Whittell, H. M., & D. L. Serventy. 1948. A systematic list of the birds of Western Australia. Public Library, Museum and Art Gallery of Western Australia, Special Publication 1: 1–126.