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Himantopus novaezelandiae

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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

Assessment Information [top]

Red List Category & Criteria: Critically Endangered D ver 3.1
Year Published: 2013
Date Assessed: 2013-11-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S.
Contributor(s): Bayliss, M., Grant, A., Maloney, R., Murray, D. & Steeves, T.
Facilitator/Compiler(s): Benstead, P., Bird, J., Butchart, S., Khwaja, N., Pilgrim, J., Symes, A., Taylor, J., Martin, R
Justification:
Despite 20 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.

History:
2012 Critically Endangered

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. Approximately 90% of the population is sedentary, but small numbers still overwinter in the North Island. 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 2001, the wild breeding population consisted of just seven pairs (Keedwell et al. 2002), but a maximum of 84 adults were recorded in the wild in August 2002 (M. Bayliss in litt. 2002). By the 2004-2005 breeding season, there were 11 productive pairs (R. Maloney in litt. 2005). Since this point the population has increased primarily thanks to the annual release of 'fast-tracked' captive-reared subadults and juveniles - 77 and 16 respectively in 2007-2008, more than 80 in 2009 and a further 70 in 2012 near Lake Tekapo (R. Maloney in litt. 2008, Anon. 2012). During 2007-2008 there were a total of 20 breeding pairs and 78 mature individuals in the wild (although it is not clear how many of these are of captive origin and have not yet bred in the wild) (R. Maloney in litt. 2008). In 2012, before the annual release of captive reared birds, the free-living population was around 130 individuals (Anon. 2012). The species's survival remains dependent on captive-rearing efforts until predator-free breeding habitat can be maintained (Keedwell 2005). Fewer than 20 dark H. novaezelandiae x H. leucocephalus hybrids are currently known (R. Maloney in litt. 2008). Cryptic hybrids are extremely rare (Steeves et al. 2010).
Countries:
Native:
New Zealand
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The estimate of 40 individuals (roughly equivalent to 27 mature individuals) is based on 20 productive breeding pairs at end of 2007-2008 season; a total of 78 'mature individuals' were counted in 2008 (R. Maloney in litt. 2008), but it is unclear how many of these were captive bred and have not yet bred in the wild successfully.
Population Trend: Increasing

Habitat and Ecology [top]

Habitat and Ecology: It breeds on braided riverbeds, but also occurs in wetlands and swamplands, and some of the population winters along the coastline in inter-tidal habitats. It feeds primarily on insects, but also takes molluscs (Anon. 2009) and small fish (Pierce 1986a). 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 three years of age. The average age is 6.8 years, and there are two birds that are older than 10 years.

Systems: Freshwater; Marine

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, D. P. Murray per A. Grant in litt. 1999) 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 (Anon. 2009). Nests are destroyed, and predation is potentially increased, by drainage and hydroelectric development, weed growth and flood-control programmes (Dowding and Murphy in press), and nesting birds are disturbed by recreational use of riverbeds. Adverse weather and natural flooding are additional, unpredictable threats (D. P. Murray per A. Grant in litt. 1999).

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
Recent advances in release methods appear to have enhanced the initial survival of released birds from 20-45% to 80-100%, but require further testing (Chambers and MacAvoy 1999). 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 recently 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 (R. Maloney in litt. 1999), and research is underway to determine the nature of the threat from each predator species (D. P. Murray per A. Grant in litt. 1999). Hybrids, now numbering fewer than 20 within the Black Stilt's range, are controlled (R. Maloney in litt. 2008). Water-levels are manipulated in managed wetlands to attract birds to feed, and possibly breed, in areas where predators are controlled (Dowding and Murphy in press). Habitat restoration is on-going, and involves the removal of exotic weeds from riverbeds (Heather and Robertson 1997). The introduction of a second population on a suitable predator-free island is desirable and has undergone a feasibility study (Murray and Sanders 2000, R. Maloney in litt. 2008), but it is unlikely that a suitable release site will be found. The species's recovery plan reportedly aims to increase the population to at least 250 breeding birds by 2011 (Anon. 2009).

Conservation Actions Proposed
Continue to monitor population trends. 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 on a predator-free island. 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 2013. Himantopus novaezelandiae. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 20 August 2014.
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