(Recurvirostridae)
Class: Aves
Order: Charadriformes
Suborder: Charadrii
Family: Recurvirostridae
Thumbnail description
Tall, slim, long-legged shorebirds with striking black-and-white plumage, long, thin, often upturned bills and a loud strident call
Size
14–20 in (35–51 cm); 5.8–16.2 oz (166–461 g)
Number of genera, species
4 genera, 8 species
Habitat
Extensive shallow wetlands with abundant invertebrate prey
Conservation status
Critically Endangered: 1 species; Endangered: 1 subspecies
Distribution
Cosmopolitan, found in most tropical and temperate regions, greatest diversity in Australian region
Evolution and systematics
Researchers tend to agree on the closest relatives of this family of elegant shorebirds; morphological, behavioral, and DNA evidence all suggest that the Recurvirostridae shares a common ancestry with the oystercatchers (Haematopodidae) and the lapwings and plovers (Charadriidae). This treatment splits the Recurvirostridae into two subfamilies; the Recurvirostrinae, comprising 3 genera (Himantopus, Cladorhynchus, Recurvirostra) and 7 species, and the Ibidorhynchinae, comprising a single genus and species (Ibidorhyncha struthersii).
While there is consensus regarding the family's relatives, the species-level relationships within the Recurvirostridae remain controversial, especially among the stilts. The genus Himantopus is recognized as having from one to six species, although most authors recognize two species; the black stilt (Himantopus novaezelandiae) and the black-winged stilt (Himantopus himantopus), and 3–5 races or subspecies of the black-winged stilt. The subspecies can be separated by plumage and biometrics, but subspecific distinction is often not discrete, there being a continuum of variation among the recognized races. Further research is required to resolve these species-level relationships.
Evolutionary origins of the recurvirostrids are thought to begin with an ancestor of the stilts and ibisbills that evolved on the shores of the ancient sea of Tethys, in the center of today's Eurasia. During the Mesozoic, as the Tethys gradually disappeared and the mountains of central Asia began to form, the ibisbill lineage may have established itself in these new mountain habitats, while the stilt lineage remained associated with the sea.
Physical characteristics
Proportionally, the stilts and avocets are the longest legged shorebirds and their legs range from crimson to blue to gray. All of the recurvirostrids have distinctive bills, and, as suggested by the genus' Latin name, are upcurved in avocets, especially in the females. The ibisbill's bill is also decurved and bright crimson in color, the stilts tend to have straight or only slightly curved bills. The blue or crimson legs and colored or curved bills combined with their black, white, and sometimes orange plumage, make the recurvirostrids conspicuous, unmistakable birds.
The ibisbill's plumage is perhaps the most striking of the recurvirostrids, with banded and barred black and white plumage. While bold, it camouflages the nesting bird remarkably well. The stilts and avocets are also dressed in patterns of black-and-white, and three species have areas of reddish-brown plumage. The black-winged stilt, the juvenile black stilt and the Andean avocet are generally black on their upperparts and white beneath. The banded stilt and other avocets are mostly white with black markings on the shoulders and wings. As with the ibisbill, breeding and non-breeding plumages are similar, the exception is the reddish-orange plumage of the American avocet (Recurvirostra americana) which is only present in the breeding season. Except for the black stilt, the juvenal plumages resemble adults', though often duller in contrast.
Overall, the stilts and avocets are long-legged, elegant birds, varying little in size. Stilts' body size ranges from 13.7–16.9 in (35–43 cm) and 5.8–9.1 oz (166–260g), and are slightly smaller than avocets whose body size ranges from 15.7–20 in (40–51 cm) and 7.9–16.2 oz (225–461 g). The ibisbill appears the most compact and sturdily built, 15.3–16.1 in (39–41 cm) and 9.5–11.2 oz (270–320 g).
Distribution
The stilts and avocets have a worldwide distribution, and are generally found in temperate and subtropical zones. The black-winged stilt is the most widespread and found in shallow wetlands of temperate and tropical regions around the world, the black and banded stilt have more limited distributions.
The avocets are found throughout temperate and subtropical Eurasia, Africa, and the Americas. Two members of the family are confined to colder, montane climates; the ibisbill in central Asia, and the Andean avocet (Recurvirostra andina) inhabits lakes of the high Andes.
Habitat
Extensive, shallow wetlands with high densities of small, invertebrate prey is the ideal habitat for stilts and avocets. The ibisbill has narrower requirements; it inhabits only rocky, slow-moving rivers. The avocets and banded stilt favor saline environments, though they often come inland to breed. The greatest variety of wetlands are used by the Himantopus stilts, which occur in habitats across a range of salinity, altitude, and water speed. Conversely, the Andean avocet remains at high altitude, saline lakes throughout the year. Opportunistic in habitat selection, stilts and avocets increasingly take advantage of man-made wetlands such as dams, irrigation sites, and sewer ponds.
Behavior
Except for the ibisbill and the black stilt, members of this family are gregarious and will feed in flocks of up to several thousand birds. Recurvirostrids feed mainly during the day, although some stilts will forage at night, especially in coastal areas where feeding activity may follow tidal cycles. When lounging, these birds gather on waterbanks in dense flocks, sit on the ground, or stand on one leg with the bill tucked under the wing, they also roost standing in the water. The ibisbill is more of a loner, although it is sometimes seen in pairs or small groups of seven or eight birds and flocks of up to 25 birds have been reported.
Except for the ibisbill, recuruirostrids nest in colonies, intermingling with other shorebirds. They are especially noisy birds when breeding, the commonest call being a bark or yelp, given as an alarm. Some species have a variety of vocalizations including different alarm calls, parental calls, and copulation calls. Ibisbills have three main calls, which have more notes than that of stilts and avocets.
Outside of the breeding season, ibisbills are quiet, keeping to themselves. They only migrate altitudinally, usually staying within their breeding range. The northern populations of the black-winged stilt, pied avocet, and American avocet migrate between temperate and subtropical regions. Some Southern Hemisphere members of this family move inland to breed, and all will move depending on the seasonal availability of wetlands.
Feeding ecology and diet
Stilts and avocets feed on a diversity of aquatic invertebrates, primarily small crustaceans and larval insects, but also some worms and mollusks (in Himantopus); small fishes and some plant matter (especially in Himantopus) is also included in the diet. All species exhibit a range of feeding techniques, the most common method is to directly peck food items. Avocets often "scythe" for food, sweeping the bill at a low angle through water or soft mud. The upcurved bill is filled with folds of thin layers of tissue (lamellae) that filter out small food items caught when scything; the bird then flicks the food into its mouth with its fleshy tongue. The banded stilts' bill also contains lamellae; lamellae are absent in Himantopus. Other feeding strategies of the stilts and avocets include plunging the entire head under water and probing for food, and snatching at flying insects.
The ibisbill has three basic feeding strategies; pecking, probing for food while waist deep in the water, and raking. Raking involves tipping its head to the side and raking its bill through pebbles in the stream-bed, dislodging small aquatic animals that it then snatches up. All recurvirostrids are able to quickly change feeding style in response to changing weather, water temperatures, water levels, and prey species present.
Reproductive biology
For data available, it appears that recurvirostrids are monogramous, although not necessarily over a whole breeding season. Stilts and avocets are generally colonial nesters, sometimes at such great densities in avocets that nests are abandoned. "Dip-shake-preen" male courtship displays are followed by copulation, and some species engage in an endearing post-copulation behavior in which the birds cross bills and walk together, the male with his wing over the back of the female. Usually three or four eggs are laid, and both parents incubate and care for the downy young.
Breeding pairs of ibisbills establish territories of 295–3,280 ft (90–1,000 m) along a river in march or early April. Both parents incubate the two eggs and rarely leave the nest unattended for more than one to two minutes. Chicks are distinctive with inordinately long toes and an already slightly upcurved bill 0.7 in (18 mm) long. Both adults feed and guard the young. When disturbed with chicks, adults fly directly at intruders, emitting a loud piping call. Adults will also fake injury to draw intruders away from chicks.
Conservation status
Most recurvirostrids have large, stable populations. Destruction of habitat by humans poses the greatest threat. Captive breeding programs have been established for the black stilt and the Hawaiian subspecies of the black-winged stilt, both of which are endangered.
Significance to humans
Most recurvirostrids enjoy a high positive profile and there are varying efforts to protect these birds and their habitat.
Species accounts
IbisbillBlack-winged stilt
Black stilt
American avocet
Pied avocet
Resources
Books:del Hoyo, J., Elliot, A. and J. Sargatal., eds. Handbook of Birds of the World. Vol. 3, Hoatzin to Auks. Barcelona: Lynx Edicions, 1996.
Fjeldså, J., and Niels Krabbe. Birds of the High Andes. Copenhagen: Zoological Museum, University of Copenhagen, 1990.
Hagemeijer, Ward, J. M. Blair, and Michael J. Blair, eds. The EBCC Atlas of European Breeding Birds. London: T & AD Poyser. 1997.
Periodicals:Chu, P. C. "Phylogenetic Reanalysis of Strauch's Osteological Data Set for the Charadriiformes." Condor 97 (1995): 174–196.
Hoekter, Hermann. "Conspecific Nest Parasitism in the Pied Avocet Recurvirostra avosetta." Ibis 142, no. 2 (2000): 280–288.
Hoetker, Hermann. "Intraspecific Variation in Size Density of Avocet Colonies: Effects of Nest-distances on Hatching and Breeding Success." Journal of Avian biology 31, no. 3 (2000): 387–398.
Robinson, Julie A., et al. "American Avocet." The Birds of North America 275 (1997).
Rojas, L. M., et al. "Diurnal and Nocturnal Visual Capabilities in Shorebirds as a Function of Their Feeding Strategies." Brain, Behavior and Evolution 53, no. 1 (1999): 29–43.
Other:Birdnet: The Ornithological Information Source.
The Sibley-Monroe Classification of Birds of the World.
Zoonomen Nomenclatural Data. (2001) Alan P. Peterson
[Article by: Rachel Ehrenberg, MS]
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