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Wrybill Anarhynchus frontalis Scientific name definitions

Popko Wiersma and Guy M. Kirwan
Version: 1.1 — Published October 24, 2023
Revision Notes

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Field Identification

20–21 cm; 43–68 g (1). Rather plump, grayish plover with conspicuous long bill curved to the right; male has black frontal bar and breastband . Female has duller, browner and narrower breastband and lacks black frontal bar. Non-breeding adult has breastband lacking or faint; no frontal bar. Juvenile as non-breeding adult, but has gray patches at sides of breast instead of breastband; feathers of upperparts have narrow dark subterminal bands, and narrow white fringes.

Systematics History

This species has been linked particularly with the Double-banded Plover (Anarhynchus bicinctus). Monotypic.

Subspecies

Monotypic.

Distribution

New Zealand: breeds in central South Island (Canterbury and Otago riverbeds); winters mainly in northern North Island.

Habitat

Breeds inland on large braided rivers, occupying large bare beds of shingle and sand, with preference for large, glacier-fed rivers, fast-flowing water and dynamic shingle banks, which do not easily become overgrown with weeds; occasionally in smaller, less braided, slower-running rivers. Outside breeding season found in shallow estuaries , on sheltered coasts with large tidal mudflats , and lagoons with soft silty or muddy substrate. Occasionally in ploughed paddocks, reclaimed saltmarsh or muddy margins of small mountain lakes and ponds.

Movement

Migratory. Moves from breeding grounds in central South Island to mudflats of estuaries and harbors on northern end of North Island. Leaves rivers late December to early February; juveniles of first nest depart before parents finish second nest. Migrates via eastern coast of South Island and western coast of North Island, probably usually in single flight, although there are occasional records at stopover sites (2); juveniles arrive in winter quarters late December to early January, and most adults mid January to February ; highest numbers present on northern coast May–July; adults show high degree of site fidelity to wintering and roosting sites. Most birds leave wintering sites in August; second-year non-breeders leave halfway through breeding season and some, mainly first-year birds, spend summer in North Island. Regularly uses stopover sites on return migration, and arrives at river mouths late August to September. Has wandered once to Chatham Islands (June 1999) (3).

Diet and Foraging

During breeding season takes aquatic invertebrates , including flatworms , annelids, gastropods, mites, spiders, and eggs, larvae, pupae and adults of various types of insect; also fish and their eggs; one study found that diet in summer was mostly adult beetles (Coleoptera), bugs (Hemiptera) and flies (Diptera) (4). Uses curved bill to probe and sweep under stones, especially for catching mayflies (see Family Text). In non-breeding areas , polychaete worms, small bivalves, crustaceans, beetles and Diptera larvae. During breeding season feeds at shallow riffles, pools and backwaters, on shingle banks and, when rivers flood, also among washed up debris; at non-breeding grounds pecks, probes and scythes on soft mud of mudflats, often at edge of receding tide. Diurnally active; in winter, night or day, depending on tide. Highly gregarious during non-breeding season, frequently in hundreds or thousands, often feeding together with other small waders.

Sounds and Vocal Behavior

Gives a somewhat Common Ringed Plover (Charadrius hiaticula)-like “weet” or “peep”, while flocks occasionally produce chittering sounds and pairs utter a bubbling trill during courtship.

Breeding

Lays late August to late October, with second clutch late October to late December. Monogamous on long-term basis. Solitary; holds vigorously defended territory in which nests and feeds, but also feeds in undefended areas; nests 400 m or more apart, rarely as close as 40 m. Home range sizes at this season generally c. 5 hectares, but up to c. 11 ha and sometimes as small as one hectare (5). Highly site-faithful and high degree of natal philopatry in juveniles, immatures and adults. Nest in sand among shingle of large, smooth, rounded stones (often 1–2 cm in diameter) commonly sheltered by large stone or piece of wood; shallow scrape lined with small pebbles. Two eggs, laid at intervals usually of less than 48 hours; double-brooded, and may lay replacement clutch; incubation 30–36 days, by both parents, but more by female, starting once clutch complete; chick has pale, uniform, off-white to gray upperparts, with indistinct gray-black flecking, white underparts; tended by both parents; fledging 35–37 days; independent immediately after fledging. Breeds first at 2–3 years old, although there is one record of a first-year female nesting (6). Hatching success 77%, fledging success 38%, i.e., 0.79 young/pair. 10% of laid eggs (47% of failed eggs) flooded, 1% of laid eggs (4%) predated. Average longevity 5.4 years; oldest recorded bird at least 16 years old and many individuals probably reach nine years of age (1).

Incubation

VULNERABLE. Hunted prior to 1940; after hunting ceased, population increased, but stabilized by early 1960s, with c. 5,000 birds. In 1994, total of 5,111 birds counted (1), with c. 85% of population congregating at the Firth of Thames and Manukau Harbor (7); more recent estimates suggest that the population currently totals 4,500–5,000 birds, with evidence from the wintering grounds of a slow, long-term decline over the last c. 40 years (8), although densities on the breeding grounds increased between 1960s and 1990s (9). Now breeds on only 26 river beds east of Southern Alps, but only numerous on ten of these. Nesting and roosting habitats, especially in lowlands, deteriorate through invasion of exotic weeds, such as broom (Cytisus scoparius) and whin or gorse (Ulex europaeus), caused by reduction of seasonal flushing of riverbeds as consequence of water abstraction. Further development, including hydro-electric schemes, threatens long-term survival of total population. Since floods are main causes of breeding failure, flood mitigation may have positive effects on breeding success, but wake from jet-boats is probably less controllable (10); however, construction of dams also destroys nesting habitat, due to permanent flooding, and predation by Kelp Gull (Larus dominicanus) may pose an increasing threat as the species becomes more numerous in association with human activities. Predation by stoats (Mustela erminea) and cats (Felis catus) has not been quantified, but is probably substantial, perhaps especially in non-breeding season (11). Nevertheless, predator control designed on behalf of the Black Stilt (Himantopus novaezelandiae) also benefits a small proportion of present species’ population (12). Further threats may include conversion of coastal habitat for aquaculture, development of windfarms and spread of mangroves.

Distribution of the Wrybill - Range Map
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  • Year-round
  • Migration
  • Breeding
  • Non-Breeding
Distribution of the Wrybill

Recommended Citation

Wiersma, P. and G. M. Kirwan (2023). Wrybill (Anarhynchus frontalis), version 1.1. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.wrybil1.01.1
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