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Himantopus novaezelandiae 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Charadriiformes Recurvirostridae

Scientific Name: Himantopus novaezelandiae
Species Authority: Gould, 1841
Common Name(s):
English Black Stilt
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Identification information: 40 cm. Black, long-legged stilt. Adult, black with long, fine, black bill. Very long red legs. Juvenile, white breast, neck, head. Black patch around eyes. Similar spp. Hybridises with Pied Stilt H. himantopus. Resulting individuals highly variable. Compared to pure adults, darker hybrid adults have longer bills, shorter legs. Compared to pure juveniles, hybrid adults have some solid black on breast. Voice Loud, high-pitched, monotonous yapping.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered D ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Bayliss, M., Grant, A., Maloney, R., Murray, D., Steeves, T. & Cleland, S.
Facilitator/Compiler(s): Benstead, P., Bird, J., Butchart, S., Khwaja, N., Pilgrim, J., Symes, A., Taylor, J., Martin, R, Ashpole, J & Stringer, C.
Justification:
Despite 35 years of intensive conservation efforts, this species remains one of the most threatened shorebirds in the world. It is classified as Critically Endangered because, although it has increased over the last decade, it still has only a tiny population. The annual release of substantial numbers of captive-reared birds, in combination with predator control, has almost certainly prevented it from becoming Extinct in the Wild, and the species's long-term survival remains dependent upon this intensive conservation management.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Himantopus novaezelandiae was formerly widespread, breeding and wintering across the North and South Islands of New Zealand, but following a long-term decline it is now restricted during the breeding season to the upper Waitaki Valley in the South Island. The population is sedentary, with small numbers of birds being sighted in other New Zealand regions. The population may have numbered 500-1,000 birds in the 1940s (Pierce 1984), by which time it had ceased to breed in the North Island and was rare as a breeding species in the lowlands. It continued to decline to a low of just 23 birds in 1981, when intensive management began (Keedwell 2005). In 1999-2000, the wild breeding population consisted of just four pairs (Keedwell et al. 2002), and a maximum of 31 adults. Since this point the population has increased primarily thanks to the annual release of 80-120 'fast-tracked' captive-reared subadults and juveniles.). In the last 15 years pair numbers have fluctuated between 8 and 23 pairs, and the total adult wild population between 39 and 93 birds. Except for one wild hatched bird, all of the adult population has been captive reared and released from either wild laid or captive laid eggs. The February 2016 population of 93 adults is the highest ever recorded since management begun. Recruitment rates from releases of juveniles or sub-adults remains very low (22-25%), and techniques for managing predators in the wild are not yet operational at the large scales needed to encompass kaki home ranges. Therefore, the species's survival remains dependent on captive-rearing efforts until predator-free breeding habitat can be maintained (Keedwell 2005). Hybridisation with H. leucocephalus was exacerbated during periods of cross-fostering of kaki eggs to pied stilt parents in the 1980’s and because low population size and the widely dispersed kaki population meant that some kaki were unable to find other kaki mates. Fewer than 5 dark H. novaezelandiae x H. leucocephalus hybrids are currently known (R. Maloney in litt. 2016), and through continued positive assortative mating, almost all kaki are pure bred. Cryptic hybrids are extremely rare (Steeves et al. 2010).
Countries occurrence:
Native:
New Zealand
Additional data:
Continuing decline in area of occupancy (AOO):No
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:3300
Continuing decline in extent of occurrence (EOO):NoExtreme fluctuations in extent of occurrence (EOO):No
Number of Locations:1Continuing decline in number of locations:No
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The estimate of 93 adults in the wild including 19 productive and 6 non-productive breeding pairs as at February 2016.  Adult age is obtained at 2 years, but some birds are not recorded breeding until age 3, so the adult wild population is made up of 38-50 breeding birds and another 40-50 birds aged 2-3 years who may be capable of breeding, but did not breed in their first season.

Trend Justification:  The number of productive breeding pairs roughly doubled during 1995-2005, to 17 breeding pairs in the wild, with a further increase to 20 productive pairs in 2007-2008, but these figures conceal a fair amount of fluctuation. Furthermore, the apparent increase is largely thanks to the annual release of captive-bred subadults and juveniles (93 birds in 2007-2008; R. Maloney in litt. 2008).

Current Population Trend:Increasing
Additional data:
Number of mature individuals:38-50Continuing decline of mature individuals:No
Extreme fluctuations:NoPopulation severely fragmented:Yes
No. of subpopulations:1Continuing decline in subpopulations:No
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:Yes
No. of individuals in largest subpopulation:100

Habitat and Ecology [top]

Habitat and Ecology:

It breeds on braided riverbeds, but also occurs in wetlands, tarns, lake deltas and swamplands. A few individuals occasionally winter along the coastline in inter-tidal habitats and many some make small local movements of a few kilometres to the river delta of their breeding valley (Pierce et al. 2015). It feeds primarily on insects, but also takes molluscs (Anon. 2009) and small fish (Pierce 1986a). Birds return to nesting area in late winter-early spring, with breeding between September and January (Pierce et al. 2015). The species is monogamous and birds pair for life (Anon. 2009). It lays four eggs and will usually re-nest if the first clutch is lost early in the season. Both birds in a pair share incubation duties (Anon. 2009). Most breed for the first time at two or three years of age.
Systems:Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):7.3
Movement patterns:Not a Migrant

Threats [top]

Major Threat(s): Predators, in particular introduced mammals such as cats, ferrets Mustela furo, stoats M. erminea, hedgehogs Erinaceus sp. and Brown Rats Rattus norvegicus, and the native Australasian Harrier Circus approximans and Kelp Gull Larus dominicanus (Pierce 1986b, Sanders and Maloney 2002) are today the primary threat, but the combined impact of habitat loss has exacerbated declines. Habitat has been lost through conversion to agriculture and hydroelectric developments (Maloney and Murray 2001). Nests are destroyed, and predation is potentially increased, by drainage and hydroelectric development, weed growth and flood-control programmes (Maloney and Murray 2001), and nesting birds are disturbed by recreational use of riverbeds. Adverse weather and natural flooding are additional, unpredictable threats (Maloney and Murray 2001). 
Hybridisation with H. leucocephalus, which was allowed to continue under former management strategies, posed a threat because the crash in the Black Stilt population made it difficult for them to form conspecific pairs and a biased sex ratio resulted in single males mating with H. leucocephalus females or hybrids (Pierce 1984, R. Maloney in litt. 1999, Steeves et al. 2010), although hybridisation has been bidirectional (Steeves et al. 2010). Extensive bidirectional hybridisation appears to have been taking place since at least 1960 (Steeves et al. 2010). The sex ratio is now even and the frequency of hybridisation has decreased (R. Maloney in litt. 2008, Steeves et al. 2010). Adjustment of the sex ratio, low reproductive success in hybrid females and high mortality are the likely reasons for a lack of widespread introgression between the two species (Steeves et al. 2010). Adult mortality in the wild remains very high (Keedwell 2005). Despite the genetic bottleneck experienced by H. novaezelandiae, there is so far no evidence of inbreeding depression in the wild (Steeves et al. 2010). However, a negative relationship has been shown between inbreeding and fitness in the captive population; in light of this care should be taken to minimise the relatedness of pairs forming in captivity (Hagen et al. 2011).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
Advances in release methods appear to have enhanced the initial survival of released birds from 20-45% to 80-100%, but require further testing (van Heezik et al. 2009). Active management involves double and triple clutching of parents by removing eggs to encourage re-laying. The removed eggs are reared in captivity. Playback calls are broadcast to juvenile birds during captive-rearing to equip them with the behavioural and auditory recognition skills necessary for survival (Galbraith et al. 2007). A study was published on the influence of release age, size of release group and size of the wild population at release sites on the post-release movements of captive-reared Black Stilts, with implications for the future management of the programme (van Heezik et al. 2009).

Predator exclusion fencing was first installed at the site near Lake Tekapo in the late 1970s (Anon. 2009). Trapping for predators around all wild nests has been on-going since 1997 (Keedwell et al. 2002), and research is underway to determine the nature of the threat from each predator species (Maloney and Murray 2001). Hybrids, now numbering fewer than 5 within the Black Stilt's range, are controlled. Water-levels are manipulated in managed wetlands to attract birds to feed, and possibly breed, in areas where predators are controlled (R. Maloney in litt. 2016). Habitat restoration is on-going, and involves the removal of exotic weeds from riverbeds (Heather and Robertson 2015). The establishment of a second population is desirable and has undergone a feasibility study (Murray and Sanders 2000, R. Maloney in litt. 2008), but without intensive site management to control weeds and pests it is unlikely that a suitable release site will be found. The species's recovery plan aimed to increase the population to at least 250 breeding birds by 2011, but this target has clearly been missed (Maloney and Murray 2001).

Conservation Actions Proposed
Continue to monitor population trends. Seek to maintain predator-free habitat for breeding within its current range. Monitor rates of habitat loss and degradation throughout the species's range. Maintain and improve productivity of the captive population, and ensure pairs forming in captivity are sufficiently unrelated to prevent potential inbreeding depression (Hagen et al. 2011). Establish a self-sustaining population at a second site. Encourage public interest and support (Reed and Murray 1993). Seek to maintain predator-free habitat for breeding within its current range. Continue efforts to prevent hybridisation with H. himantopus, and maintain parity in the adult sex ratio in order to avoid conditions under which introgression with H. himantopus could occur (Steeves et al. 2010).


Citation: BirdLife International. 2016. Himantopus novaezelandiae. The IUCN Red List of Threatened Species 2016: e.T22693690A93418187. . Downloaded on 11 December 2016.
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