Black Stilt

Identificazione

Black stilts are a medium-sized (220 g) wader with extremely long pink legs, red eyes, distinctively black plumage, and a long slender black bill. Juveniles have a white breast, neck and head, with a black patch around the eyes, and black belly feathers that distinguish them from pied stilts. Black adult plumage appears in their first or second year. Black plumage may be an adaptation to "absorb heat better in the cold, windswept habitat of glacial riverbeds and lakeshores".<p>Hybrids between black and pied stilts are very variable in their plumage, but usually have black breast feathers, which pied stilts never do.

Tassonomia

Black stilts are one of several species in the genus Himantopus, classified along with avocets in the family Recurvirostridae. Although genetically and behaviourally distinct from pied stilts (Himantopus himantopus), they are able to successfully hybridise with them. Hybridisation and dilution of the gene pool is one reason black stilts are threatened with extinction. Black and pied stilts in New Zealand represent two colonisations of pied stilt ancestors from Australia: the first, long ago, giving rise to melanistic descendants, the second in the early 19th century.

Nome scientifico

Himantopus novaezelandiae

Autorità

Gould, 1841

Ordine

Caradriformi

Famiglia

Recurvirostridae

Genere

Himantopus

Areale e habitat

Although black stilts currently breed only in braided river systems in the South Island, subfossil bones show that prior to human arrival they were found in habitats as diverse as narrow bush streams in Hawkes Bay, and a wetland lake surrounded by forest in North Canterbury. In the nineteenth century they bred on riverbeds and in wetlands of the central and eastern North Island and most of the South Island except Fiordland. As late as the 1940s they were still common in South Canterbury and Central Otago, and nesting occurred in Central Otago as late as 1964. Throughout their range they have been almost entirely replaced by pied stilts, which colonised New Zealand after human settlement and now number approximately 30,000.<p>Currently black stilts breed only in the upper Waitaki River system in the Mackenzie Basin. Most black stilts will also overwinter in the Mackenzie Basin, but about 10% of the population, especially hybrids and those paired with pied stilts, migrate to North Island harbours such as Kawhia and Kaipara in January for the winter.

Areale riproduttivo

AU : c South I. (New Zealand)

Areale non riproduttivo

to North I. (New Zealand)

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: in aumento.

Tendenza della popolazione

in aumento