AUSTRALIAN 2 OLSEN, TROST & MYERS FIELD ORNITHOLOGY Ninox owls on the island of Sumba, Indonesia: Above — Sumba Boobook near Wanga, Below — Little Sumba Hawk-Owl near Lewa Plate 2 Photos: J. Olsen & S. Trost 3 AUSTRALIAN FIELD ORNITHOLOGY 2009, 26, 2–14 Owls on the Island of Sumba, Indonesia JERRY OLSEN1, SUSAN TROST2 and SUSAN D. MYERS3 1Institute for Applied Ecology, University of Canberra, Canberra, Australian Capital Territory 2601 244 Wybalena Grove, Cook, Australian Capital Territory 2614 317A Park Street, Hawthorn, Victoria 3122 Summary Four owl species are said occur on the island of Sumba, Indonesia: Eastern Barn Owl Tyto javanica sumbaensis, Eastern Grass Owl T. longimembris, Sumba Boobook Ninox rudolfi, and the recently discovered Little Sumba Hawk-Owl N. sumbaensis. We describe behaviour, including vocalisations, of all except the Eastern Grass Owl, provide measurements of Eastern Barn Owl and Sumba Boobook specimens, including the first published weights, and the first egg measurements for Eastern Barn Owls on Sumba. We discuss the taxonomy of the Eastern Barn Owl and Sumba Boobook, and support a change of common name for Sumba Boobook to Sumba Hawk-Owl. Studies are urgently needed to determine the status and conservation of all four owl species said to occur on Sumba. Introduction The island of Sumba lies at 10°S and 120°E in the Lesser Sunda chain in south- eastern Indonesia (see Olsen & Trost 2007 for a description). Del Hoyo et al. (1999) listed three owls for Sumba. We add the recently discovered Little Sumba Hawk-Owl Ninox sumbaensis (Olsen, Wink et al. 2002) to Table 1. Much of what has been written about the owls on Sumba has been material repeated from previous sources, with no new observations. Here we add new observations and discuss these in relation to published sources. Wink et al. (2008) noted that morphology is often invariant in many owl species, but their distinctive calls, which are inherited and not learned, are of considerable taxonomic value, so we recorded calls of three Ninox species (two on Sumba and, for comparison, one in Australia) and discuss the relevance of these. Methods On three trips to the island (July 2001, December 2001–January 2002 and June–July 2002) JO and ST concentrated on finding and photographing the Sumba Boobook Ninox rudolfi and the newly described Little Sumba Hawk-Owl (Olsen, Wink et al. 2002) at two Table 1 Owls recorded on Sumba, Indonesia, after del Hoyo et al. (1999) and Olsen, Wink et al. (2002), using the most recent taxonomy of Christidis & Boles (2008). *Endemic species. Eastern Barn Owl Tyto javanica sumbaensis Eastern Grass Owl Tyto longimembris Sumba Boobook Ninox rudolfi* Little Sumba Hawk-Owl Ninox sumbaensis* AUSTRALIAN 4 OLSEN, TROST & MYERS FIELD ORNITHOLOGY places: (1) in an inland forest ~600 m above sea level near Lewa, 49 km west of the main town of Waingapu (9°44′42″S, 119°59′6″E), and (2) in coastal lowland at Wanga near Melolo 42 km east of Waingapu (9°51′53.6″S, 120°37′57″E) in a deciduous and mangrove forest close to the ocean. No specific attempts were made to find other species, although we did look for Eastern Barn Owls Tyto javanica sumbaensis in three church buildings in the town of Waingapu (9°39′27″S, 120°15′39″E) and in a limestone canyon south of Waingapu (9°47′24″S, 120°18′57″E). We also noted the date and location of any owls seen or heard along the road. Calls and behaviour of all owls were noted. Playback of taped territorial calls of the Sumba Boobook and Little Sumba Hawk-Owl (provided by M. Linsley) and Southern Boobook Ninox novaeseelandiae (recorded by JO and ST in Canberra, ACT) were broadcast to elicit responses from owls. Moulted feathers found by JO at a church at Waingapu, and at an abandoned pump-house at Wanga, presumed to be from Barn Owls, were sent to Michael Wink, University of Heidelberg, Heidelberg, Germany, for genetic analysis (DNA profiling). Buildings and trees were searched for nests in Waingapu and Wanga, but only one, a deserted nest of a Barn Owl in an abandoned building at Wanga, was found; both intact eggs were measured with callipers. On Sumba, men and boys often kill birds and bats with air rifles and shanghais. We never encouraged this activity, but a specimen of a Barn Owl and of a Sumba Boobook previously killed were located and weighed with a Pesola spring balance and measured with callipers. Following the Biological Species Concept, König et al. (1999) regarded as full species the members of a reproductive community that have evolved different patterns from members of another reproductive community. Often with owls these patterns are most easily perceptible in their vocalisations. Owls’ vocalisations are inherited and, unlike some passerines, have little geographic variation in dialect, so they are diagnostic of species and critical to the study of owl taxonomy (Higgins 1999; König et al. 1999). For a mean 140 minutes per night JO and ST observed and video/audio-recorded episodes of calling with a Panasonic NV-MX300 digital video-camera (a) three different calling pairs of Little Sumba Hawk-Owls over five nights near marker Km 49, and (b) four different calling pairs of Sumba Boobooks at four different locations over 13 nights: three pairs near Melolo, and one pair near Km 49 in the same forest as the Hawk-Owls, calling at the same time as, and within 50 m of, a pair of them. The calls of each owl species were digitised from a Panasonic NV-MX300 digital videotape with an IBM microcomputer and were sampled at 44.1 kHz. Cool Edit Pro (version 1.2) was used to produce sonagrams. SDM made recordings of a single Little Sumba Hawk-Owl (one of a pair in a remnant patch of forest) and a single Sumba Boobook (at the edge of forest), with a Marantz PMD660 solid-state recorder with Sennheiser K6 microphone, at marker Km 51 ~3 km east of Lewa on the Lewa–Waingapu road, on 4 and 3 August 2007, respectively. Sonagrams were generated using Raven. Results Eastern Barn Owl Tyto javanica sumbaensis Calls: adults gave a rasping call typical of Common Barn Owls T. alba (Bunn et al. 1982). A juvenile in a limestone canyon 15 km south of Waingapu gave a rasping food-begging whine typical of the Eastern Barn Owl (as described by Higgins 1999). We saw Eastern Barn Owls on the following occasions. 11–12 July 2001, 1845 h, Waingapu Lutheran Church: two individuals perched in the church tower (Plate 3). Moulted feathers, collected from the beams and inside the church tower under these two individuals, were sent for DNA analysis (see p. 6). 14 July 2001, 1930 h, along road 57 km west of Waingapu and 1 km east of Lewa: two Eastern Barn Owls were observed for 10 minutes in the middle of a rice field, perched in low trees. VOL. 26 (1–2) march–JUNE 2009 Owls of Sumba, Indonesia 5 Eastern Barn Owl, tower of Lutheran Church, Waingapu, Sumba, Indonesia Plate 3 Photo: J. Olsen & S. Trost Eastern Barn Owl eggs from nest in the attic of an abandoned pump-house near Wanga, Sumba, Indonesia Plate 4 Photo: J. Olsen & S. Trost AUSTRALIAN 6 OLSEN, TROST & MYERS FIELD ORNITHOLOGY 15 July 2001, 1825 h, rice field 15 km west of Melolo: one Eastern Barn Owl observed for 5 minutes, screeching, sitting in a tree on the edge of cleared field. 18 July 2001, 1829 h, 15 km south of Waingapu: an apparent fledgling, in a limestone canyon sunk into the plain with dry forest above it, heard food-begging (screeching), apparently from a pothole in the rocks. 28 December 2001, Wanga, 1906 h: an Eastern Barn Owl landed in the top of dead tree in farmland (rice and cattle) 100 m away from a Sumba Boobook calling from a tree; no interaction was seen between the two owls. 24 June 2002, 1600 h, near Wanga: an old nest was found in the attic of an abandoned brick- walled building formerly housing a water-pump. Three white eggs, and primary feathers, assumed to be from the incubating female, were resting on debris, castings, rotting wood and other materials. One egg was broken; the two intact eggs measured 41.9 × 32.9 and 41.1 × 33.4 mm (Plate 4). 1 July 2002, 1600 h: a freshly dead Eastern Barn Owl was found on the road between Waingapu and Lewa. Measurements (mm) were: wing 275, tail 107.4, mid-toe with talon 33.6, mid-toe talon 12.8, inner talon 16.1, hind talon 18.6, culmen without cere 23.0; wing- formula 9/8/10/7 from the outside; and weight 385 g. Eastern Barn Owls were the commonest owl seen along roads at night on Sumba. Some could have been misidentified Eastern Grass Owls Tyto longimembris, though most were close enough to identify unequivocally as Barn Owls. Twice we saw an Eastern Barn Owl on farmland close to Sumba Boobooks, with no apparent conflict. Examination of prey remains of Eastern Barn Owls living in Waingapu suggested that the most common prey items were rats (Muridae), fruit-bats (Pteropodidae), and Eurasian Tree Sparrows Passer montanus. Wink et al. (2004, 2008) concluded that moulted feathers from the Wanga and Waingapu individuals were genetically distant enough from the Common Barn Owl to constitute a possible separate species. Recordings of calls were not of high enough quality for analysis. Eastern Grass Owl Tyto longimembris No calls were recorded.