With no confirmed records for this species for well over a century, and evidence of continuing habitat loss and degradation within its extremely small range, its population is thought likely to be tiny, if indeed it survives. This bleak prognosis necessitates its classification as Critical.
DISTRIBUTION This species (see Remarks 1) is known only from the island of Siau, north of Sulawesi, Indonesia, where the only record is as follows: n INDONESIA Siau a single specimen collected on the island in 1866 (Schlegel 1862–1873).
POPULATION Nothing is known of the numbers of this species, but given the size of the island, which is in any case highly volcanic with unvegetated upper reaches (J. C. Wardill verbally 1999) combined with the information under Threats, it seems likely that the original population was always small and that any surviving population will prove minute (but see Remarks 2). In August 1998 two nights were spent listening for owls on the island and on one occasion some distant hissing in thick vegetation may have been young owls begging (F. R. Lambert in litt. 1999). In October 1998 interviews with local people proved fruitless,except that some claimed that 20 years ago an owl had been fairly common and was now rare
The distribution of Siau Scops-owl Otus siaoensis: (1) Siau Island. Historical (pre-1950) SIAU SANGIHE 1741
owing to hunting, although this could in any case have referred to Brown Hawk-owl Ninox scutulata (J. C. Wardill in litt. 1999). However, in January 1999 an Action Sampiri team member from Siau reported that people from his village, Hiung, are familiar with at least two species of owl, both brown and small, so there is still hope that the Siau Scops-owl survives (J. Riley in litt. 1999).
ECOLOGY Habitat The species was presumably originally a forest-dweller. Food It presumably feeds or fed on nocturnal invertebrates like other members of its genus.
Breeding There is no information.
THREATS Siau is very small, and is currently experiencing rapid deforestation (Riley 1996).In 1995 there was some lowland forest around Lake Kepetta in the south of the island, but by 1998 this had been felled (J. Riley in litt. 1999). In August 1998 the island was judged to have been largely converted to mixed plantation and scrub, but small patches of low treessurvived (F. R. Lambert in litt. 1999). In October that year a five-day survey determined that only 50 ha of forest remains (but see Remarks 3), all above 800 m on Gunung Tamata in the centre of the island, and only accessible through the village of Lai on the island’s west side; two nights of surveys in the forest were, however, rendered inconclusive by heavy rain (J. C.Wardill in litt. 1999).
MEASURES TAKEN The only action to date has been the first brief searches for this species (see above). In October 1998 five days were also spent on the island of Tagulandang, just south of and almost as large as Siau, but only a few hectares of forest were found to remain, all above 600 m (J. C. Wardill in litt. 1999).
MEASURES PROPOSED The 50 ha of forest at the top of Siau, and the few hectares left on Tagulandang, need to be surveyed thoroughly (at different times of year), and this is planned to begin in 2000 (J. C. Wardill in litt. 1999). Another investigation of any patches of trees lower down on Siau is also required, however remote the possibility of success may seem (see Remarks 2). There are several smaller islands in the group which might also bear investigation. If the species is rediscovered, intervention will urgently be needed to achieve habitat conservation through agreements with the local communities.
REMARKS (1) This owl has be shown to be sufficiently distinctive to warrant its resurrectionas a full species, even in the absence of vocal evidence (Lambert and Rasmussen 1998). (2) The Sangihe Scops-owl Otus collari has proved to be highly adaptable to secondary habitat including coconut groves and gardens (Lambert and Rasmussen 1998), so it is by no means inconceivable that this species has adjusted likewise, although of course this is no more than speculation. (3) It is not entirely clear if the small patches of forest reported by F. R. Lambert were considered in this survey.
Shekelle, M. and Salim, A. 2007. Siau Island Tarsier, Tarsius sp. In: Primates in Peril: The World’s 25 Most Endangered Primates 2006–2008, R. A. Mittermeier et al. (compilers), p.12. Unpublished report, IUCN/SSC Primate Specialist Group (PSG), International Primatological Society (IPS), and Conservation International (CI), Arlington, VA.