The birds is a distinctive wading bird, which possesses a uniquely bent bill. The tip of the black bill is curved to the right, this adaptation allows these birds to forage under stones for insect larvae(3). The plumage is ash-grey above with white underparts. During the breeding season, individuals have a black band across the upper chest and males also have a band on the forehead (2).
The laying season runs between September and October; a clutch of two eggs is laid into a slight depression amongst the gravel. Both parents take it in turn to incubate the eggs that are well camouflaged against the shingle, resembling the stones around them (4). The parents also rely on camouflage to remain undetected with their ash-grey plumage barely visible amongst the stones (4). The chicks are able to leave their nest within a day of hatching and follow their parents on foraging trips (4).
Birds begin to leave the breeding grounds by late December; this species is one of the first of the season to begin its migration (4). Using its specially adapted beak, the birds is able to forage under stones for invertebrates such as mayfly larvae(3).
Large flocks of wrybills were recorded in the early 19th century but the species has since undergone a long-term decline, principally as a result of habitat loss at breeding sites (2). The shingle beds that comprise the nesting habitat of this species have decreased in size due to the encroachment of weeds, and altered river flooding regimes caused by hydroelectric schemes (2). It is also likely that predation by introduced stoats (Mustela erminea) and cats has played a large part in the decline of this ground-nesting bird (2).
The birds became fully protected in New Zealand in 1940 (2). Research is currently being undertaken into the impact of predation on birds population numbers (2). Long-term monitoring is vital in determining the overall trends in this threatened species (2).
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