Wrybill

Anarhynchus frontalis

SUBFAMILY

Charadriinae

TAXONOMY

Anarhynchus frontalis Quoy and Gaimard, 1830, New Zealand. Monotypic.

OTHER COMMON NAMES

English: Wry-billed plover, crook-bill plover; French: Pluvieranarhyngue; German: Schiefschnabelregenpfeifer; Spanish: Chorlitejo Piquituerto.

PHYSICAL CHARACTERISTICS

7.75–8 in (19.7–20 cm); weight: males 2.1 oz (59.5 g), females 2.0 oz (56.7 g). Unique in having a bill that bends to the right at about a 12° angle. White forehead extends backwards. Dark gray band extends from bill, continues under eye, gradually lightening toward crown. Crown is nearly black where it meets white forehead. Rest of upperparts are uniform bluish gray, including wing coverts that are edged in white. Flight feathers are brown with outermost flight feathers gray with white edges. A broad, black band covers upper breast. Bill is black and legs are dark gray. Female similar, but breast band paler and narrower and crown is light where it meets white forehead. Breast band absent in juveniles and winter plumage.

DISTRIBUTION

Canterbury and Otago, South Island, New Zealand. Winters mainly on the Firth of Thames at Manukau Harbor, and on the Kaipara River, North Island, New Zealand.

HABITAT

Nest on large expanses of stones near rivers. During nonbreeding season most often found on silty mudflats near high tide mark on sheltered coasts and estuaries.

BEHAVIOR

Large pre-migratory flocks at the Firth of Thames perform elaborate mass aerial displays.

FEEDING ECOLOGY AND DIET

Probes in mud, but also sweeps the bill sideways, capturing tiny crustaceans from water surface. Also pecks and probes between stones and sweeps tiny invertebrates from under stones in riffle areas. Feeds on spiders, insects, crustaceans, small mollusks, small fish, and eggs. Larval mayflies and caddisflies are commonly eaten.

REPRODUCTIVE BIOLOGY

Have strong fidelity to breeding territories and even nest sites. Birds often pair with same mate in consecutive years, perhaps because of nest site tenacity. Breeding does not occur until second or third year. Typically nest on higher banks and parts of islands in wide areas of shingle with fairly large stones. Male forms scrape, lined by pebbles flicked into the scrape or regurgitated from the crop. Clutch size is two. Parental duties are shared. One male shared incubation of a four-egg clutch with two females. Incubation requires about 31 days, and young fledge at about 29 days. Typically nest again after first clutch fledges.

CONSERVATION STATUS

Classified as Vulnerable; population of 3,000–5,000 birds appears to be declining. Breeding habitat is deteriorating due to increasing recreational use of rivers and to invasion of weeds, apparently as a result of hydroelectric plants upriver. Predation by stoat (Mustela erminea), cats, and kelp gulls (Larus dominicanus) is probably significant.

SIGNIFICANCE TO HUMANS

Shot for sport until protected in 1940.