Siau Scops-Owl Otus siaoensis Scientific name definitions

Only known specimen measured 19 cm; wing length 125 mm; tail length 55 mm; no data on mass (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Small scops-owl (distinctly smaller than nearest congeners, O. manadensis and O. collari) with short ear-tufts, fairly large head and relatively short wings and tail. Crown buffy brown with black streaks and fine vermiculations; nape and mantle buffy brown with rufous tinge, black streaks and whitish-buff mottling; pale buffish nuchal collar; indistinct pale scapular stripe (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Facial disc brownish orange-buff with indistinct brown concentric lines; underparts brownish orange-buff, generally paler than upperparts, darkest on upper breast, with broad dark streaks and dark vermiculations (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Irides yellow; bill and cere yellowish horn; tarsi feathered nearly to base of toes (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Juvenile plumage unknown.

Probably part of a species-group centred on O. manadensis (which see). Known from a single specimen. Until recently, treated as conspecific with O. manadensis, but separated during analysis that established O. collari, to which it is closest in morphology but from which it differs in its much smaller size (127 vs mean 161; allow 3); longer ear-tufts (at least 1); “more heavily marked and less conspicuously pale” throat (1); lack of “prominent pale nuchal collar” (2); “much more vermiculated, more regularly barred, and drabber” underparts (2); “fewer bands” on remiges and rectrices (ns[1 or 2]); “much more broadly, irregularly, and less strongly banded” tail (ns[1 or 2]) (2 Lambert, F. R., and P. C. Rasmussen (1998). A new scops owl from Sangihe Island, Indonesia. Bulletin of the British Ornithologists’ Club 118(4):204–217. Close ). Monotypic.

Siau I, N of Sulawesi.

Recently described as a rolling, two-note “"Ook-grrrrah” that lasts c. 0·7 seconds and is repeated regularly (3 Eaton, J. A., B. van Balen, N. W. Brickle, and F. E. Rheindt (2016). Birds of the Indonesian Archipelago: Greater Sundas and Wallacea. Lynx Edicions, Barcelona, Spain. Close ).

CRITICALLY ENDANGERED. CITES II. Restricted-range species: endemic to Siau I, N of Sulawesi and present in Siau EBA. Known only from the holotype, collected in 1866. Given the small size of this island, and general lack of vegetation on volcanic upper slopes, the original population cannot have been large BirdLife International (2015) Species factsheet: Otus siaoensis. Downloaded from http://www.birdlife.org on 16/01/2015. . With only 50 ha of forest remaining any surviving population must be tiny, even if it adapts to plantations and scrub, like congeners such as Sangihe Scops-owl (O. collari) (4 Butchart, S.H.M., Collar, N.J., Crosby, M.J. and Tobias, J.A. (2005). “Lost” and poorly known birds: top targets for birders in Asia. BirdingASIA. 3: 41–49. Close ). Encouragingly, accounts by local people indicate that it might persist; nevertheless a 32-day survey in 2006 failed to find the species, as did several additional searches in 2009 BirdLife International (2015) Species factsheet: Otus siaoensis. Downloaded from http://www.birdlife.org on 16/01/2015.  and 2016 (5 Kelly, J., A. Rahman, I. Grass, J. S. Tasirin, and M. Waltert (2017). Avifaunal status updates, range extensions and potential new taxa on the lesser Sangihe and Talaud islands, Indonesia. Raffles Bulletin of Zoology 65:482–496. Close ). Further searches are needed to determine whether the species is still extant (6 Collar, N.J. and Sykes, B.R. (2009). Lost, found and saved—OBC conservation: the next 25 years. BirdingASIA. 11: 41–46. Close ) and it has been suggested that a tiny, unsurveyed remnant of primary forest on N slope of Karangetang volcano, which is probably accessible only by boat, offers the best chance of rediscovering the species (5 Kelly, J., A. Rahman, I. Grass, J. S. Tasirin, and M. Waltert (2017). Avifaunal status updates, range extensions and potential new taxa on the lesser Sangihe and Talaud islands, Indonesia. Raffles Bulletin of Zoology 65:482–496. Close ).