Stilts and Avocets (Recurvirostridae)

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Stilts and avocets

(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

List of Species

Ibisbill
Black-winged stilt
Black stilt
American avocet
Pied avocet

Ibisbill

Ibidorhyncha struthersii

subfamily

Ibidorhynchinae

taxonomy

Ibidorhyncha struthersii Vigors, 1832, Himalayas. Taxonomy still unresolved, often placed in own monotypic family.

other common names

French: Bec-d'ibis tibétain; German: Ibisschnabel; Spanish: Picoibis.

physical characteristics

15.6–16.4 in (39–41 cm); 0.59–0.7 lb (270–320 g), bill 2.6–3.2 in (68–82 mm). Distinctive wader with long, decurved, crimson bill and striking plumage. Dark brown or black face with white margin towards neck. Neck and upper back bluish gray, lower back brownish gray and white belly with broad black band. Legs grayish purple. Female and male similar, female marginally larger with slightly longer bill. Juvenile browner with less clearly marked plumage and paler coloring, bill dark pinkish gray. Unlike stilts and avocets, salt glands are nearly absent in ibisbill.

distribution

Southeastern Kazakhstan, south to Kashmir and east through northwestern China, Tibet, and northeastern India to eastern central and northern central China. Mainly in major mountain systems of central Asia.

habitat

Flat, stony, rivers at high altitudes (1,640–14,435 ft [500–4,400m]), may occur as low as 330 ft (100 m) in winter.

behavior

Territorial, solitary breeders, may roost together outside of breeding season. Rarely fly unless disturbed.

feeding ecology and diet

Feeds during the day, usually singly. Feeds by pecking, probing, or raking bill through gravel, often forages breast deep in water. Specializes on insect larvae, occasionally eats small fish.

reproductive biology

Monogamous and territorial, incubation by both sexes. Generally lays four eggs in April or May in a shallow, sometimes pebble-lined pit in ground. Eggs usually greenish-gray with brown speckles, chicks hatch mid-May through late June and led away from nest by female as soon as they dry, brooded up to 23 days. Can fly when 45–50 days old.

conservation status

Not threatened, range is extensive an in areas with few humans. However, ibisbills are adapted to rather restricted habitat, so could be vulnerable to habitat destruction from industrial mining of gravel from river-beds and building of hydro-electric plants. Nest trampling by sheep, predation by foxes and disturbance by humans can also be a problem. Species not known to have been kept in captivity, as of 2001 no captive-breeding programs are in operation.

significance to humans

None known.

Black-winged stilt

Himantopus himantopus

subfamily

Recurvirostrinae

taxonomy

Charadrius himantopus Linnaeus, 1758, southern Europe. Forms superspecies with black stilt (Himantopus novaezelandiae), sometimes considered conspecific. Races can be split into three groups ("nominate" race, "pied" race, and "black-necked" race) and 2–5 separate species recognized.

other common names

English: Common stilt; French: Échasse blanche; German: Stelzenläufer; Spanish: Cigüeñuela Común.

physical characteristics

13.7–15.7 in (35–40 cm), 5.8–7.2 oz (166–205 g). All have extraordinarily long, pink legs and long black, straight or slightly upcurved bills. Male's back and wings black, sometimes with greenish sheen, white below, gray banding on white tail. Upper parts of female dullish brown. Juvenile resembles adult female. Races differ in head and hindneck plumage color, from mainly white to continuous black. Sexual dimorphism is more evident in some races.

distribution

H. h. himantopus Linnaeus, 1758, France and Iberia south to sub-Saharan Africa and Madagascar, east to central Asia and northern central China, Indochina, Taiwan, and Indian subcontinent. H. h. leucocephalus Gould 1837, Java east to New Guinea, south to Australia and New Zealand; winters north to Philippines, Greater Sundas, and Sulawesi. H. h. knudseni Stejneger, 1887, Hawaiian Islands. H. h. mexicanus P.L.S. Mäller, western and southern United States to Central America, West Indies, to southwestern Peru, eastern Ecuador, and northeastern Brazil. H. h. melanurus Vieillot, 1817, northern Chile and eastern central Peru through Bolivia and Paraguay to southeastern Brazil, and south to south central Argentina.

habitat

Temperate and tropical shallow wetlands. Usually breeds in freshwater, including lake edges, marshes, swamps, river-beds and flooded fields, also found in coastal salt marshes.

behavior

Gregarious, may feed in flocks of several thousand birds. Alarmed birds often head-bob. Call is a sharp monosyllabic "yep" or "kek." Sometimes performs a high-leaping display with a "floating" descent, the significance of this performance isn't clear. "Mob-display" also observed, whereby a few birds come together and behave in a mildly aggressive fashion for no apparent reason.

feeding ecology and diet

Diet strongly seasonal depending on habitat. Preys on various aquatic invertebrates including insects, small mollusks, crustaceans, and worms, as well as small fish and their eggs, and tadpoles. Active forager, employs a variety of methods to capture prey. Well-adapted to nocturnal vision, these birds will feed on windy, moonless nights.

reproductive biology

Usually breeds in colonies of two to 50 pairs. Timing of breeding quite variable over range. Nests often widely spaced on ground or among grasses, sometimes a well-lined, floating mass of water weeds. Incubation of four eggs 22–26 days, by both sexes. Fledging 28–37 days.

conservation status

Not globally threatened but controversial taxonomy calls for monitoring at subspecific level. Hawaiian subspecies knudseni is endangered, survival depends on predator control and protection of nesting habitat. As of 2001 only 1,800 birds. Nominate race was in decline in the 1800s, but has rebounded with population estimates now at minimum of 21,000 pairs.

significance to humans

None known.

Black stilt

Himantopus novaezelandiae

subfamily

Recurvirostrinae

taxonomy

Himantopus novæ-zelandiæ Gould, 1841, Port Nicholson, North Island, New Zealand. Forms superspecies with H. himantopus sometimes considered conspecific. Monotypic.

other common names

French: Échasse noire; German: Schwarzer Stelzenläufer; Spanish: Cigüeñuela Negra.

physical characteristics

14.5–15.7 in (37–40 cm); 7.7 oz (220 g). Long pink legs, distinctive plumage; all black with greenish gloss on back and wings. Shorter legs and longer bill than H. himantopus. Female similar to male, usually shorter legs. Non-breeding adult has grayish white chin and forehead. Juvenile has black wings and back, white below, develops grayish black markings on white areas first winter. Plumage of hybrids with H. h. leucocephalus variable, often with black collar and black markings on belly and breast.

distribution

New Zealand, was widespread but now restricted to MacKenzie Basin central South Island, small numbers winter in North Island.

habitat

Ponds, lakeshores, river-beds and swamps of MacKenzie Basin. Some visit coastal estuaries and lagoons outside of the breeding season.

behavior

Defends some sort of territory all year, an exception in the Recurvirostrids. Outside of the breeding season more gregarious, though it will still defend feeding territories.

feeding ecology and diet

On riverbed breeding grounds feeds primarily on aquatic insect larvae and small fish. In stiller waters eats various aquatic insects, worms, and mollusks. Probes with bill beneath stones for food, and employs the scything method which is commonly used at night and especially effective with worms.

reproductive biology

Seasonal breeder, usually September–January. Lays four eggs in a well-lined nest bowl, near water, usually solitary and will defend territory. Incubation 24–26 days, by both sexes. Fledging 41–55 days, first breeding at two years. In wild many eggs and chicks are eaten by introduced predators.

conservation status

Critically Endangered. Habitat loss, predation on eggs after introduction of carnivorous animals to island, and interbreeding with H. himantopus all contribute to decline. Population crashed in late 1950s from 1,000 birds to fewer than 100, where it remains today. Captive-breeding, anti-predator, and habitat restoration programs began in the 1980s have had some success in reducing population decline.

significance to humans

None known.

American avocet

Recurvirostra americana

subfamily

Recurvirostrinae

taxonomy

Recurvirostra americana Gmelin, 1789, North America. Monotypic.

other common names

French: Avocette d'Amérique; German: Braunhals-Säbelschnäbler; Spanish: Avoceta Americana, Piqocurvo.

physical characteristics

16.1–2.0 in (41–51 cm); 10.6–16.2 oz (302–461 g). Large, striking birds legs bluish, strongly upcurved black bill. The only avocet with annual color change, the head, neck, and breast change from gray to orange-brown in breeding season. Wings and back black, contrasting with white on wing coverts. Sexes similar in plumage, male often larger, bill shorter and more strongly recurved in female. Juvenile resembles adult but crown pale brown with dull chestnut nape and hindneck.

distribution

Southeastern British Columbia east to southwestern Ontario, south to northern Baja California east to central Texas, eastern United States, and central Mexico. Winters from California and south, Texas through Mexico to Guatemala and irregularly to northern Honduras, southeastern United States and Bahamas to Cuba.

habitat

Specializes in using ephemeral wetlands of arid western United States, breeds around sparsely vegetated saline lakes and ponds, in large numbers at marshes of Great Salt Lake, Tulare Basin of California and across northern Great Basin. Outside of breeding season occurs in freshwater habitats and coastal lagoons and estuaries.

behavior

After flock arrives at breeding grounds, transition from flocking to territoriality. Territory defended by male and female. "Upright posture," where the bird faces its opponent with neck extended vertically, is used to threaten other birds.

feeding ecology and diet

Mostly feeds on aquatic invertebrates while wading or swimming, also crustaceans, worms, small fish, and seeds. Scything

is hallmark method, but also pecks, plunges, and snatches. Will forage in dense flocks.

reproductive biology

Monogamous, though pair bond doesn't usually extend past one season. Semi-colonial nesting, nest is a grass-lined depression in soil. Usually four eggs, incubation 22–29 days by both sexes. Both adults care for chicks, fledging four to five weeks.

conservation status

Not threatened. Before 1900s shooting and trapping led to population declines, particularly on the Atlantic coast. Many wetlands used by American avocets in western United States have been contaminated with selenium as a result of irrigation and other human activities, loss of wetland habitat has led to population declines. Operators of selenium-contaminated ponds in California's Tulare Basin now required to provide mitigation habitat for breeding recurvirostrids, and species response has been favorable.

significance to humans

Considerend a game bird in early 1900s in California.

Pied avocet

Recurvirostra avosetta

subfamily

Recurvirostrinae

taxonomy

Recurvirostra avosetta Linneaus, 1758, Italy. Monotypic.

other common names

English: (Eurasian) avocet; French: Avocette élégante; German: Säbelschnäbler; Spanish: Avoceta Común.

physical characteristics

16.5–17.7 in (42–45 cm); 7.9–14 oz (225–397 g). Distinctive, black, strongly upcurved bill and long-blue gray legs. Plumage white with black forehead, crown to beneath eyes and nape and upper hindneck. At rest has three black bands on mantle and wings. Female bill shorter with stronger curve. Juvenile resembles adult but black plumage tinged brown and white upperparts have brown or gray mottling.

distribution

Europe through western and central Asia to southeastern Siberia and northeastern China, through northern Africa to eastern and southern Africa. Winters from western Europe and Africa through Middle East to northwestern India and southeastern China.

habitat

Breeds in dry and sparsely-vegetated flat, open areas, usually shallow saline lakes, lagoons and estuaries, up to 9,840 ft (3,000 m). Outside of breeding season found in muddy tidal flats, rarely at freshwater lakes and rivers.

behavior

Gregarious, engages in elaborate mating ceremony. Adults give "broken wing" display to distract predators from young. Makes frequent clear flutish calls of "kluit, kluit."

feeding ecology and diet

Mostly feeds by picking, also scything, takes variety of aquatic invertebrates. Winter diet dominated by worms, will feed by sight on the siphons of mollusks. Sometimes feeds communally.

reproductive biology

Breeds April through August, nests in large colonies. Nest is a grass-lined depression in open ground or short vegetation. Lays three to five eggs, brownish with dark spots or blotches. Incubation 23–25 days, by both sexes, fledging 35–42 days. Conspecific nest parasitism documented, parasitic eggs laid earlier in the season into nests of other pied avocets. Known to have lived over 24 years in the wild.

conservation status

Not threatened. Has rebounded from range contraction in northwestern Europe in 1800s, number of breeding pairs in Europe estimated at 31,000–56,000 with greatest numbers in Denmark, Netherlands and Spain. Less opportunistic than other recurvirostrids, this is cause for concern as pressure on wetland habitat increases due to lack of protection and contamination from pollutants including selenium.

significance to humans

During successful conservation effort of early 1900s in Europe, the pied avocet was adopted as the Royal Society for the Protection of Birds' symbol, and the image is strongly associated with ornithological conservation.

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.