Australian Field Ornithology 2019, 36, 18–23 http://dx.doi.org/10.20938/afo36018023 Nest, egg, incubation behaviour and parental care in the Huon Bowerbird Amblyornis germana Richard H. Donaghey1, 2*, Donna J. Belder3, Tony Baylis4 and Sue Gould5 1Environmental Futures Research Institute, Griffith University, Nathan 4111 QLD, Australia 280 Sawards Road, Myalla TAS 7325, Australia 3Fenner School of Environment and Society, The Australian National University, Canberra ACT 2601, Australia 4628 Utopia Road, Brooweena QLD 4621, Australia 5269 Burraneer Road, Coomba Park NSW 2428, Australia *Corresponding author. Email: [email protected] Abstract. The Huon Bowerbird Amblyornis germana, recently elevated to species status, is endemic to montane forests on the Huon Peninsula, Papua New Guinea. The polygynous males in the Yopno Urawa Som Conservation Area build distinctive maypole bowers. We document for the first time the nest, egg, incubation behaviour, and parental care of this species. Three of the five nests found were built in tree-fern crowns. Nest structure and the single-egg clutch were similar to those of MacGregor’s Bowerbird A. macgregoriae. Only the female Huon Bowerbird incubated. Mean length of incubation sessions was 30.9 minutes and the number of sessions daily was 18. Diurnal incubation constancy over a 12-hour day was 74%, compared with a mean of ~70% in six other members of the bowerbird family. The downy nestling resembled that of MacGregor’s Bowerbird. Vocalisations of a female Huon Bowerbird at a nest with a nestling are described and illustrated. Introduction Study site and methods Birds build a remarkable variety of nests of different After a 6-week exploratory trip by RHD and David Bryden architecture, size and nest materials, and place them in the Adelbert Mountains, the Huon Peninsula, and around in various sites (Winkler 2016) but perhaps the most Tari, PNG, in July–August 2014 to find a suitable site to extraordinary structures built by birds are the maypole study robins (Donaghey 2015), RHD selected Camp 12 bowers built and decorated by promiscuous males of as a base camp in the remote intact forest of the Yopno the polygynous bowerbird species of Prionodura and Urawa Som Conservation Area (YUS CA, named after the Amblyornis (Ptilonorhynchidae) (Cooper & Forshaw 1977; Yopno, Urawa and Som Rivers) on the Huon Peninsula. Diamond 1982, 1986; Frith 1989; Coates 1990; Frith & Frith In addition to studying the parental care of robins there, 2000, 2009). Males of polygynous bowerbird species build we opportunistically observed the nesting behaviour of the elaborate bowers of species-specific design decorated with Huon Bowerbird and some other songbird species. ornaments that function to attract and impress females. Female bowerbirds visit the bowers of different males to TB, DJB and RHD flew into Sapmanga (elevation observe their bowers, displays and vocalisations to choose 900 m asl) on 21 October 2014, arranged porters and guides a mate (Borgia 1985; Uy & Borgia 2000; Uy et al. 2000). at Gomdan village and walked up to Camp 12 (elevation Females of polygynous bowerbirds build the nest, lay and 2300 m asl; 06°01′S, 146°50′E), where we stayed from incubate the eggs, and provide all parental care alone 23 October to 6 December 2014. One of our guides, (Frith & Frith 2004, 2009). George Sinao, discovered a Huon Bowerbird nest with an egg in it on the afternoon of 17 November. We visited the A female bowerbird collected in the Rawlinson Ranges, nest-site (2470 m asl) with him, in the early afternoon of Huon Peninsula, north-eastern Papua New Guinea 19 November. When a camera was held 30 cm from the (PNG) was named Amblyornis subalaris (macgregoriae) nest, the incubating bird flew up into the inner canopy of germanus (Rothschild 1910). We follow Beehler & Pratt an understorey tree, and was identified as a female Huon (2016), who elevated the Huon Bowerbird A. germana Bowerbird. The single egg was photographed, weighed to species status based on its distinctive bower, which with a digital electronic balance to the nearest 0.1 g, and exhibits characteristics of the bowers of both Streaked measured with callipers to 0.1 mm. To determine the A. subalaris and MacGregor’s A. macgregoriae Bowerbirds incubation behaviour by this female, RHD set up a portable (see Beehler & Pratt 2016 for descriptions of bowers and hide before 0800 h on 24 November, and then RHD and their sites), different plumage and morphometrics, and DJB alternated 2-h nest-watches spanning all daylight courtship vocalisations (Baylis 2015; Beehler & Pratt hours from 0800 to 1800 h on 24 November, and from 2016). The Huon Bowerbird inhabits the mountains of 0600 to 0800 h the following morning. RHD also recorded the Huon Peninsula at elevations of 1660–2940 m above incubation behaviour for 2 hours on 29 November and sea-level (asl) (Beehler & Pratt 2016). Here we document 2 hours on 30 November. for the first time the nest-site, nest, egg, and incubation rhythm of the Huon Bowerbird, and female vocalisations at TB returned to the YUS CA with SG from 29 September to a nest with a nestling. 29 October 2016 and from 6 October to 17 November 2017, Breeding biology of Huon Bowerbird, New Guinea 19 to record bird vocalisations. They established a base camp at Camp Astrapia (elevation 2009 m asl; 06°01′S, 146°49′E). Two Huon Bowerbird nests, one with a single egg and the other with a downy chick, were found in 2016, and two nests, each with a single egg, in 2017. TB and SG described the nest-sites, and recorded the altitude, height above the ground and dimensions of the nests and eggs, and photographed the nest-sites, nests, eggs and nestling. TB recorded the vocalisations of a female that visited the nest with the nestling and used a DPA4060 omnidirectional microphone placed ~30 cm from the nest with a long lead run to a Nagra LB recorder, file type WAV 48 kHz/24bit. The recorder was run for 1 hour 35 minutes and a selection (cut 161020_115427_USER1435 lodged both at the British Library of Wildlife Sound, UK, and Macaulay Library, Cornell Lab of Ornithology, USA) was used to prepare the spectrogram using Raven Pro 1.4, Hann window with a FFT1024 (the Fast Fourier Transformation value). Figure 1. Nest 1 and egg of Huon Bowerbird, Yopno Urawa Rainforest was present at both Camp 12 and Som Conservation Area, Huon Peninsula, PNG. Photo: Camp Astrapia but, because of our short stays, the Richard H. Donaghey plants there could not all be identified (from fruit and flowers). However, Inaho (2012) has described the mid-montane rainforest in a 1-ha plot 2400 m asl near Camp 12: there was a high stem density (mean 25 stems/0.4 ha) and a tree height of mostly 10–20 m, dominated by one species (Platea excelsa) in the family Icacinaceae. Nine other plant families, in order of family importance value (FIV), were Cunoniaceae, Rubiaceae, Sapindaceae, Sapotaceae, Rutaceae, Monimiaceae, Escalloniaceae, Melastomataceae and Symplocaceae (Inaho 2012). The FIV was determined by the relative density, relative diversity and basal area (m²) of stems. No Moraceae species were encountered in his upper plot (2400 m asl) but there were eight in a 1-ha plot lower down (2100 m asl: Inaho 2012). Rainforest vegetation at Camp Astrapia was not described by Inaho (2012). During our stays at Camp 12 in October–December 2014 and Camp Astrapia in 2016 and 2017, there was little sunshine and heavy rain fell most afternoons, evenings and some Figure 2. Egg of Huon Bowerbird from Nest 1. Photo: mornings. Donna J. Belder Results Table 1. Three of the four nests found in 2016–2017— Nest 2 (Figure 4), Nest 3 (Figure 5), and Nest 4—were in tree-fern crowns. Nest 5 (Figure 6) was in the fork of a large- Nest-site, nest, egg and incubation period leaved shrub. The altitude of the five nests ranged from For Huon Bowerbird Nest 1 (2014), the foundation and 2009 to 2616 m asl. Mean height of these nests above the external walls of the open-cup-shaped nest consisted of ground was 1.94 m (range 1.0–2.5 m). The dimensions of sticks, and the inner walls were composed of large dry Nests 1 and 5 are given in Table 1. Four of the nests each leaves and twigs. The egg-cup was lined with small twigs. contained one egg. The dimensions of two of the eggs The external diameter of the nest was 160 mm and the are given in Table 1. Nest 3 contained a single nestling depth was 100 mm. The internal diameter of the egg-cup (Figure 5). was 120 mm and the depth was 60 mm. The nest was 1 m above ground in a dense tangle of brambles and ferns well-concealed from above (Figure 1, Table 1). Incubation rhythm and behaviour The single egg measured 42.0 mm × 28.8 mm and was Only the female incubated the single-egg clutch. uniform pale buff (Figure 2). Only the female incubated Incubation constancy during the nest-watch (which totalled (Figure 3). When last inspected by RHD at 1320 h on 12 h: 0800–1800 h on 24 November and 0600–0800 h on 6 December 2014, Nest 1 contained one warm egg. Thus 25 November 2014) was 73.6% and averaged 75% for the incubation period from the afternoon of 17 November the first 4 hours, 73% for the next 4 hours and 73% for to 6 December was 19+ days. the last 4 hours of daylight. Hourly incubation constancy The altitude, site, height above the ground, and contents ranged from 58.7% to 86.6% (Table 2).