Australian Field Ornithology 2020, 37, 161–165 http://dx.doi.org/10.20938/afo37161165 Is there an owl species on St Matthias (Mussau) Islands, Papua New Guinea? Thierry Quelennec and Marianne Quelennec 9 rue d’Alsace, 29290 Saint-Renan, France. Email: [email protected] Abstract. In July 2019, during a short ornithological visit to the St Matthias (Mussau) Islands, Papua New Guinea, we recorded a sound that might have been from an owl on the small island of Emussau close to Mussau. No owl or nightjar is known to occur on these islands. The bird’s call shows similarities but differs from other Melanesian Ninox owl species. Here we describe the call and discuss potential origins. Introduction Between 22 and 27 July 2019, we visited the St Matthias Islands (also known as Mussau Islands) in Papua New Guinea. Our main goal was to search for and observe the Mussau Thrush Zoothera [heinei] eichhorni (a taxon that is likely to be considered a full species, split from the Russet-tailed Thrush Z. heinei) and to observe other bird species. This archipelago is 160 km north-west of Kavieng, the main town of New Ireland, from where we took a small boat to reach the St Matthias Islands. We visited the main island of Mussau, two small islands Eloaua and Emussau, and two smaller islets (Figure 1). The St Matthias Islands are considered an Endemic Bird Area by BirdLife International (2020), while Mussau has been identified by Beehler (1993) as an important area for terrestrial biodiversity in Papua New Guinea and as a high priority for further biological survey (BirdLife International 2020). The islands contain four endemic bird species (Dutson 2011) and 15–17 endemic subspecies. Despite this high degree of endemism, the avifauna remains poorly known and the islands are infrequently visited by ornithologists (see Cuthbert 2015 for a summary of avian surveys). The difficulty in reaching these islands is probably one explanation for this. Figure 1. Islands of the Saint Matthias Archipelago, Papua Observations New Guinea. Emussau Island is south of the large Mussau Island. I = island. Source: CartoGIS Services, College of Asia and the Pacific, The Australian National University. On 26 July 2019, we spent a day prospecting Emussau (also known locally as ‘Small Mussau’), a small island off the south-eastern tip of Mussau (Figure 1). The island is rounded, 670 m in diameter and 1.4 km² in area, and 149°39′26″E), 100 m from the sea and ~10 m above sea covered by secondary growth and plantation forest. Only level, we heard a strange sound, which we transcribed one family inhabits this island, and behind the houses as Kwow. It immediately reminded us of a Ninox owl call of the tiny settlement there is a Coconut Cocos nucifera (the Manus Boobook N. meeki has a similar tone but a plantation beyond which are clearings for agriculture. faster rhythm), although no owl species is known to occur The bird species on Emussau were similar to those on the St Matthias group. While we continued with other on Eloaua (which we had surveyed the previous days: observations, the owl-like song persisted through the Appendix 1) although the numbers of each species twilight. Another individual started to call, closer to us than differed between the islands. We focused on the Mussau the first one. We considered alternative explanations for Thrush, the main purpose of our trip, all day and until it was this sound, such as frogs or mammals, but the origin of the evening. At 1800 h (sunset), in degraded forest very close sound moved from one place to another in the way only a to a coconut plantation next to the houses (1°33′12″S, flying bird does. We followed the sound through secondary 162 Australian Field Ornithology T. Quelennec & M. Quelennec growth near a plantation, but it repeatedly changed genus Ninox when shown the field guide Birds of New positions from one tree to another, its call always emanating Guinea (Gregory 2017). He described an owl call and the from the lower canopy, ~17–20 m above the ground. After time of vocal activity as being between 1830 and 1900 h. c. 10 minutes, the presumed bird was duetting or duelling He claimed to have seen the owl in lowland scrub but not with the other perhaps 100–200 m away. We managed to dense forest, although very few people would remain in approach to just under the tree from where one of the calls dense forest on Mussau at night. was emanating but could not see the bird because of the dense foliage. We tried to record the call several times but No owls were recorded in the 11-day Wildlife Conservation struggled with the loud background noise from the frog Society expedition in 2014 despite 11 days spent at two chorus during the early night. Our only recordings, made locations on Mussau Island (Cuthbert 2015). Cuthbert with a ROLAND R-07 recorder and without a directional (2015) listed the collectors, ornithologists and birders who microphone or parabola (see link to recording at https:// have visited Mussau; none has reported any owl, and no www.xeno-canto.org/584096), were saturated with this new resident forest species has been discovered since the background noise, making it difficult to hear the call clearly. 1920s (Tarburton 2020). However, when Dutson (in litt. We tried playback of the recording, but the sound of the 2020) spent several nights on Mussau in 1997, he noted frogs overwhelmed the call in question (both the recording a similar call at sunset that a local resident identified as and the playback) and this was not effective. At 1820 h, belonging to a ‘long-legged bird’. This was subsequently the presumed bird flew away and continued calling a few identified as a Black Bittern Ixobrychus flavicollis based times further away from us before it stopped. Following on this species being heard on several different islands in the observation, the recording was edited using a low- subsequent months, including in some dry forests on small pass filter in the program Audacity, adjusting the threshold islands as well as along coasts. visually and aurally until the sound became more clearly We did not actively explore Mussau Island by night. On audible (the spectrogram has all noise >~1.5 kHz removed Eloaua (7.7 x 1.3 km, and much bigger than Emussau), we and the sound amplified multiple times courtesy of Frank did not hear any similar calls around our camp (1°34′41″S, Rheindt) (see Figure 2 and recording at https://www.xeno- 149°38′07″E), although twice we walked for 1 hour in the canto.org/584098). period from early evening to dark. Our local native guide from Eloaua did not know of any owl there. Discussion The call No species of owl is known to occur in the St Matthias group (Gregory 2017), but nearly every large island in this part of We compared this call with the calls of other birds, notably Papua New Guinea (Manus, New Ireland including New Ninox species in nearby Melanesian islands—Manus Hanover or Lavongai, New Britain, Bougainville including Boobook N. meeki, New Ireland Boobook N. variegata, Buka) has its own boobook (Ninox) species (Dutson 2011; New Britain Boobook N. odiosa and Solomons Boobook Gregory 2017). The St Matthias Islands are smaller and N. jacquinoti. We had previously heard the Solomons more remote than these other islands, but it is perhaps Boobook N. j. eichhorni on Bougainville and Isabel and surprising that Ninox owls should be absent from Mussau. there are recordings of all four of these Ninox species After making our recordings, we found someone with on xeno-canto.org. The call that we heard on Emussau knowledge of the birds and nature on this island, a man is clearly different (although see below). It is a loud working with a logging company in the hills of Mussau’s Kwow repeated every 6–10 seconds monotonously main island. He told us that he has seen owls on the (Figure 2). There are differences between all the calls main island (where he spends most of his time) but not of the Melanesian Ninox species (see above): the call on Emussau (where he returns only for the weekends). of the Manus Boobook is a series of 4–10 notes grro, He was able to recognise without hesitation owls in the groo, groo-groo-groo groogroogroogroogroogroo, and Frequency (kHz) Frequency Time (seconds) Figure 2. Spectrogram of suspected Ninox owl species on Emussau Island Is there an owl species on St Matthias (Mussau) Islands, PNG? 163 the Solomons Boobook gives a series of reverberating References chong notes (Dutson 2011). However, the type of call and Beehler, B. (1993). Papua New Guinea Conservation Needs habits of the bird (i.e. calling at dusk during a short period, Assessment, Volume 2: The Biodiversity Support Program. calling from the canopy or subcanopy) that we heard are Corporate Press Inc., Landover, Maryland, USA. consistent with a Ninox owl. Dutson (2011) reported that BirdLife International (2020). Endemic Bird Areas factsheet: St Ninox owls call at dusk but rarely at night and are often Matthias Island. http://datazone.birdlife.org/eba/factsheet/194 duetting (although Olsen et al. 2002a and Olsen & Trost (retrieved 7 February 2020). Cuthbert, R. (2015). Birds of Mussau. In: Whitmore, N. (Ed.). 2007 suggested this could be duelling in other Ninox A Rapid Biodiversity Survey of Papua New Guinea’s Manus species). We compared the call with the two different calls and Mussau Islands, pp.