|Scientific Name:||Prosobonia cancellata|
|Species Authority:||(Gmelin, 1789)|
|Red List Category & Criteria:||Endangered B1ab(ii,iii,iv,v) ver 3.1|
|Reviewer/s:||Butchart, S. & Symes, A.|
|Contributor/s:||Blanvillain, C., Burle, M., Lank, D., Pierce, R. & Raust, P.|
This species was formerly widespread, but is now restricted to predator-free, usually uninhabited islands. It is listed as Endangered because it has a very small range overall, is currently known only from a few locations, and is likely to be undergoing a continuing decline owing to the effects of introduced species, and to a lesser extent, habitat degradation. If predators were to become established on Tenararo and Morane (which hold 80% of the population) the species would warrant uplisting to Critically Endangered.
|Range Description:||Prosobonia cancellata is endemic to the Tuamotu Archipelago, French Polynesia, where it has declined during the last century and possibly also the 19th century. The type specimen was collected on Kiritimati (= Christmas Island), Kiribati (Walters 1993). This population was probably eliminated by introduced cats and rats and its taxonomic relationship with Tuamotu birds is unclear (Pierce and Blanvillain 2004). Only five islands are now thought to support populations: Tenararo (a minimum of 500 in 2001), Morane (a minimum of 530 in 2003), Reitoru (estimated at 57 in 2003), Tahanea (estimated at 185 in 2003, 59 in 2007, c. 150 in 2009, 168 at the beginning of 2011 and 74 at the end of that year, following a massive die-out (through starvation) of the population in the month following an entry of saltwater into the water tables of the islets caused by a strong swell [M. H. Burle in litt. 2012]) and a very small population (no estimate available) on Raraka, near Tahanea. Elsewhere in the Tuamotu Archipelago, one bird was seen on Aratika in 2007 (P. Raust in litt. 2007), another on Raroia atoll (Levy 2011) and two on Raroia in 2008 (J-Y. Meyer, pers. comm. to M. H. Burle in litt. 2012) and otherwise small numbers of birds were reported in the 1980s and 1990s, most notably from Fakarava (reports from fishermen in the 1980s and one seen 2003) and Anuanuraro (30-40 in 1990) (Lacan and Mougin 1974, Holyoak and Thibault 1984, Thibault 1988, Lovegrove et al. 1989, Seitre and Seitre 1991, C. Blanvillain in litt. 1999, P. Raust in litt. 1999, Blanvillain et al. 2002, Pierce et al. 2003, Pierce and Blanvillain 2004). There have been an increasing number of nil returns when islands where small numbers had been reported are re-surveyed, implying a continued decline correlated with the spread of rats Rattus spp and cats (Pierce and Blanvillain 2004). Consequently, populations on the latter three islands may already be extinct and records of small numbers of individuals elsewhere may refer to visiting (rather than established) birds (Blanvillain et al. 2002). It is unlikely that many more populations will be discovered, although the Duke of Gloucester Islands and Marutea Sud warrant surveys (Pierce and Blanvillain 2004). The population is estimated to be 1300 individuals.|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The population is estimated to number at least 1,300 individuals based on surveys by Pierce in 2003, reported on in Pierce and Blanvillain (2004). This roughly equates to 870 mature individuals.|
|Habitat and Ecology:||It is found on upper beaches of coral rubble and sand amongst dwarf srubs (especially Scaevola, Messerschmidti and Guettarda) and scattered tall shrubs, as well as in adjacent areas of shrubland and interior of forest, especially open forest (Pratt et al. 1987, Pierce and Blanvillain 2004). Dense stands of Pandanus and coconut trees Cocos nucifera are avoided (Pierce and Blanvillain 2004) when they outcompete the shrub layer. The species is regularly reported along atoll shorelines and lagoon edges (Pratt et al. 1987), but it is thought they only frequent these habitats when attracted out of curiosity to the observers (Pierce and Blanvillain 2004). It is non-migratory but may visit islands where it does not nest (Pratt et al. 1987). Food, which comprises mainly invertebrates, seeds, nectar and some plant material, is gleaned from the vegetation of scrubs and trees and also from the surface of the ground and in leaf litter (Pierce and Blanvillain 2004, M. H. Burle in litt. 2012).|
|Major Threat(s):||The introduction of rats, particularly black rat Rattus rattus, and cats Felis catus, has eliminated the species from all but the most infrequently visited islands in the archipelago (Pratt et al. 1987,. Pierce and Blanvillain 2004). The establishment of coconut Cocos nucifera plantations is thought not to be a threat unless native undergrowth is also cleared (Pierce and Blanvillain 2004) or outcompeted by seedlings when plantations are not harvested (M. H. Burle in litt. 2012). Abandoned coconut plantations are thus another important cause of habitat loss, for instance on many islets of Tahanea and possibly, to a much greater extent, on Tenararo (M. H. Burle and D. B. Lank in litt. 2012). Moreover, the establishment of coconut plantations can increase the frequency of human visits to islands and consequently the likelihood of predator introduction (Pierce et al. 2003, Pierce and Blanvillain 2004). Of particular concern is that the two neighbouring islands to Tenararo, where there is coprah, support rats Rattus spp. (Pierce et al. 2003, Pierce and Blanvillain 2004). An additional concern is that visiting birdwatchers, as well as local fishermen and coconut crab Birgus latro harvesters, may accidentally introduce rats to Tenararo and Morane, the latter of which merits reserve status (Pierce et al. 2003, P. Raust in litt. 2007). The dramatic effect of a swell witnessed in 2011 (a 55% population crash in less than a month due to starvation as a result of vegetation, and possibly arthropod, die-out [M. H. Burle and D. B. Lank in litt. 2012]) proved the negative effects of sea level rise to the species. As such, the effects of climate change, particularly sea level rise, are likely to be a significant threat to the species in the future.|
Conservation Actions Underway
Information on this species has been collected as a result of expeditions in 1999 and follow-up work in 2001 and 2003, as well as work conducted on Tahanea in 2008/2009 and 2011 (M. H. Burle in litt. 2012). Manu has developed an action plan to eradicate rats on Vahanga (adjacent to Tenararo) with technical support from the New Zealand Department of Conservation, Pacific Invasives Initiative, BirdLife International, SOP and Island Conservation and funding from CEPF. In 2011, Island Conservation, the USFWS, and the RSPB conducted rat eradications on Palmyra Atoll and Henderson Island respectively in 2011. In 2013, it will be established whether such actions were successful and whether these islands could thus be considered for future translocations of Tuamotu Sandpipers.
Conservation Actions Proposed
Maintain the predator-free status of Morane and Tenararo by restricting access. Eradicate predators from motus (islets) where the species is no longer present on the atolls Tahanea and Reitoru to allow it to re-colonise these naturally. Survey islands where historical records indicate that the species may still persist, particularly Marutea Sud, Maria, and islands in the Duke of Gloucester Group (Pierce and Blanvillain 2004). Also re-survey Reitoru prior to decisions on rat eradications. Identify suitable islands for translocation, either rat- and cat-free or where eradication is possible, taking into consideration a number of physical, social and biological parameters (SPREP 1999, Pierce and Blanvillain 2004). Eradicate rats from such islands. Consider translocating birds to islands on which predators have been eradicated where the species never occurred but which supported now extinct species of Prosobonia. Develop a recovery plan (SPREP 1999, Pierce and Blanvillain 2004). Involve local people in the implementation of the recovery plan, with the species as its emblem, so that they associate it with increased coprah and coconut crab yields which will result from rat eradication.
|Citation:||BirdLife International 2012. Prosobonia cancellata. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 26 May 2013.|
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