The New Zealand black stilt, or Kakï, is one of the most threatened wading birds in the world (1). This slender wading bird is very distinctive with its completely black plumage, long red legs and fine black bill (3). Juveniles go through various black and white phases before becoming fully black at around 18 months (4). Eggs are ovoid and light green or brownish olive with dark brown markings (2).
Adults are monogamous and pairs generally stay together for life (2). The breeding season peaks in October and both the male and female build the nest that consists of a depression in the ground lined with grass, twigs and waterweeds (3). The pair take it in turns to incubate the four eggs, and care for the chicks (2).
Black stilts use their slender beaks to prize prey from underneath stones and to skim through muddy water (4). They feed mainly on aquatic invertebrates, small fish and molluscs(2).
Breeding now occurs only within the Mackenzie basin, a high plateau in New Zealand's South Island (5). Most nests are on braided riverbeds (where the river separates, exposing parts of the riverbed), but individuals can also be found on the shores of lakes and in wetlands (6). New Zealand black stilts are partially migratory; some birds move to lower coastal sites prior to winter, and some sub-adults winter in the north of the North Island, whilst others remain in the high basin throughout the year (5).
The massive decline and retraction in range of the black stilt is mainly attributed to the introduction of mammalian predators to New Zealand such as cats, ferrets and stoats (6). In the Mackenzie Basin, ongoing large-scale rabbit control programmes since the 1940s may have forced feral cats to switch to hunting native birds instead (3). Habitat modification has also contributed to the decline of this species (1); a massive hydroelectric scheme in the basin has considerably altered the natural habitat (7). Today, mammalian predators still represent the major threat to the continued survival of this species along with hybridisation with the closely related Australasian pied stilt, which successfully colonised New Zealand subsequent to European settlement in the 1800's (6). Since the 1970's, the small remnant breeding population of black stilts has been restricted in range to the Mackenzie Basin where it has been intensively protected and managed (5). If numbers continue to fall, hybridisation will become an even bigger problem as individuals find it harder to find mates within their own species.
Since the mid-1900's, pure black stilts have numbered fewer than 100 individuals; in 1999, numbers fell as low as 40, only 9 of which were females (6). Since the 1970's, intensive predator control, protection and manipulation of wild nests, and captive breeding and release programmes have been the only factors preventing this species from becoming extinct in the wild (5). The New Zealand Department of Conservation set out a new Kakï Recovery Plan in 2001 (3) in a concerted effort to save this species. Phase one of the plan aims to increase numbers in the wild through captive rearing and release programmes along with predator control measures (3). The second phase of the Recovery Plan aims to identify the causes of breeding failure in the wild (3). Recent improvements in release techniques have increased the initial survival of released birds to as much as 80 to 100 percent and these are encouraging results (6), although factors that inhibit recovery remain.
A species or taxonomic group that is only found in one particular country or geographic area.
Cross-breeding with a different species.
Animals with no backbone.
A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
Having only one mate during a breeding season, or throughout the breeding life of a pair.
Merton, D., Reed, C. and Crouchley, D. (1999) Recovery strategies and techniques for three free-living, critically-endangered New Zealand birds kakapo (Strigops habroptilus), black stilt (Himantopus novaezelandiae) and takahe (Porphyrio mantelli). Proceedings the 7th World Conference on Breeding Endangered Species, 0: 151 - 162.
BirdLife International. (2000) Threatened Birds of the World. Lynx Edicions and BirdLife International, Barcelona and Cambridge.
Sanders, M.D. (1999) Effect of changes in water level on numbers of black stilts (Himantopus novaezelandiae)using deltas of Lake Benmore. New Zealand Journal of Zoology, 26: 155 - 163.
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