BirdLife Species factsheet for Mountain Starling: http://datazone.birdlife.org/species/factsheet/mountain-starling-aplonis-santovestris
The Mountain Starling, Aplonis santovestris, is endemic to cloud forest above 1,200m in the mountains of Espiritu Santo, Vanuatu. The species has been recorded from three of the highest mountains on the island (Mt Watiamasan, Mt Tabwemasana and Pic Santo), but records have been limited and sporadic (recorded in 1934, 1961, 1991 and 2010) (Harrison and Marshall 1937, Reside 1991, Bregulla 1992, S. Totterman in litt. 2010 per G. Dutson in litt. 2016). Local villagers have described the species to be widespread and common, but it appears to be very localised and at very low population densities (Harrison and Marshall 1937, Reside 1991, Bregulla 1992, S. Maturin in litt. 1994), and despite the recent record in 2010, several observers have trekked to suitable altitudes on the island and failed to locate the species (Barré et al. 2011, J. Mittermeier and L. Szucs pers. comm. 2016 per G. Dutson in litt. 2016).
The species is currently listed as Vulnerable under criteria D1+2 on the basis that it has an estimated small population, known only from a few locations (see BirdLife International 2017). This is, in part, based on a population size estimate of 250-999 mature individuals, which is derived from an assessment of range size, descriptions of abundance and known records, and fits with population density estimates for congeners/close relatives of a similar body size and the fact that only a proportion of its range is occupied. However, given the paucity of recent records it is possible that the population size is actually less than this and may in fact be better placed in the range 50-249 mature individuals (G. Dutson in litt. 2016).
The paucity of records does also mean that it is very difficult to try to estimate its recent population trend, although it has been suggested that the species has declined since historical records, and potentially since 1991 (G. Dutson in litt. 2016). There are plausible threats to the species, with the Man Hill people reportedly eating this species (S. Maturin in litt. 1994), though they rarely visit the altitudes where this species lives and so the validity of this report has been queried (S. Totterman in litt. 2007). It should be noted though that a number of other Pacific montane starling species have become extinct, presumably through the introduction of predatory mammals or disease (Pratt et al. 1987); and while Santo has no native land mammals but introduced species such as cats, dogs and rats are now widespread. Therefore, we may infer that the species is undergoing a continuous decline.
This may give sufficient information to provide a new Red List category and criteria for this species, but we do request further information and comments to best decide the correct listing for this species. Below we outline the assessment against all of the criteria.
A: the rate of population decline has not been estimated and so we cannot give a clear assessment against this criterion.
B: this species has a newly calculated MCP Extent of Occurrence of 450km2. The species is inferred to be declining, though habitat and range loss is unlikely as clearance is generally confined to lowlands and lower hills (Barré et al. 2011). The species is currently listed as occurring at 2-5 locations*. It is suggested that this be retained, because even though the main threat is likely to be invasive species, the starling’s disjunct, high altitude habitat means that it could be less likely that this threat would rapidly affect all individuals. However, given this information the species still does warrant listing as Endangered under criterion B1ab(v).
C: the species is currently considered to encompass one sub-population, despite occurring in disjunct areas. If this is retained and the new population size (<250 mature individuals) is accepted, then the species would meet the threshold for Critically Endangered under criterion C2a(ii). If the new population size is not accepted, the species would warrant listing as Endangered under criterion C2a(ii). However, if we consider the species to occur as disjunct sub-populations, then the species may still warrant listing as Endangered or Critically Endangered (based on whether the current or newly proposed population size estimate is used), but under criterion C2a(i) instead; though we would require further information regarding sub-population size estimates to confirm this.
D: if the newly proposed population estimate is used, the species would meet the threshold for Endangered under this criterion.
E: to the best of our knowledge no quantitative analyses regarding extinction risk to this species have been conducted, so this species would not warrant listing under this criterion.
Therefore, given the current available information the species likely warrants at least uplisting to Endangered under criterion B1ab(v). However, to more thoroughly and correctly assess this species we request further information and comments, particularly regarding population size and structure to best decide which category and criteria this species should be listed under.
*Note that the term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).
Barré, N., Delsinne, T. and Fontaine, B. 2011. Terrestrial Bird Communities. In: Bouchet P., Le Guyader H. and Pascal O. (eds), The Natural History of Santo, MNHN, IRD, PNI, Paris.
BirdLife International. 2017. Species factsheet: Aplonis santovestris. Downloaded from http://www.birdlife.org on 30/03/2017.
Bregulla, H. L. 1992. Birds of Vanuatu. Anthony Nelson, Oswestry, U.K.
Harrisson, T. H.; Marshall, A. J. 1937. Aplonis santovestris sp. nov. (Type description). Bulletin of the British Ornithologists’ Club LVII: 148-150.
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.
IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN.
Pratt, H. D.; Bruner, P. L.; Berrett, D. G. 1987. A field guide to the birds of Hawaii and the tropical Pacific. Princeton University Press, Princeton.
Reside, J. 1991. Mataweli is alive and well: the search for the Santo Mountain Starling. Wingspan: 10-11.