Eurylaimus javanicus, Horsfield, 1821

Gulson-Castillo, Eric R., Pegan, Teresa M., Greig, Emma I., Hite, Justin M., Hruska, Jack P., Kapoor, Julian A., Orzechowski, Sophia C., Shipley, J. Ryan & Winkler, David W., 2019, Notes on nesting, territoriality and behaviour of broadbills (Eurylaimidae, Calyptomenidae) and pitas (Pitidae) in Tawau Hills Park, Sabah, Malaysian Borneo, Bulletin of the British Ornithologists’ Club 139 (1), pp. 8-27 : 15-17

BANDED BROADBILL Eurylaimus javanicus

Encountered daily, but at lower density than Black-and-yellow Broadbill ( Fig. 1 ). These species have been reported at similar densities in Sarawak ( Fogden 1976), but our observation that Banded Broadbill is less common agrees with observations from Brunei (C. F. Mann pers. comm.).

This species shared the Black-and-yellow Broadbill’s repertoire of wing and bill displays (see above). Such displays have not been previously reported for Banded Broadbill ( Lambert & Woodcock 1996, Wells 2007). The context and patterns of these were similar to Black-and-yellow Broadbill displays. We also saw displays performed near a nest ( ML 479554). Birds displayed both when accompanied by conspecifics, and apparently when alone. Soft calls accompanying displays were lower pitched and less squeaky than those made by Black-and-yellow Broadbills when wing-displaying ( ML 480261; Fig. 2).

We found what appears to be the first nest of the species to be described on Borneo ( Smythies 1999). It was under construction and suspended from the thick, serrated, drooping leaves of a large epiphytic Pandanus sp. ( Fig. 5 ) growing c. 15–20 m above ground in the lowest crotch of a Koompassia excelsa tree at the edge of a clearing with a densely vegetated swamp, at c. 290 m elevation. The completed nest, which we subsequently collected and is now in the Sabah Parks Vertebrates Collection, was 25 cm tall, 22.5 cm wide and 15 cm deep. Its outward appearance was of a rounded, oblong tangle of vines (c. 1 mm thick, some with leaves), narrow black fibres, twigs (c. 2–3 mm thick) and scattered leaves. The entrance to the inner chamber was near the top of the tangle, directly below the Pandanus leaves from which the nest was suspended. It faced away from the tree trunk and the epiphyte, and was 54 mm tall by 58 mm wide. Mean thickness of the walls around the entrance was 35 mm. Diameter of the inner cavity at the nest entrance was 11.6 cm; the inner cavity was lined with thick, flat grass stems and leaves.

The nest leant against the tree trunk. It was almost entirely supported by a 44 mm-thick bundle of fibres slung around one of the Pandanus leaves, but some stray vines were connected to other leaves nearby. The location was relatively unobscured by branches and received ample sunlight: this Koompassia excelsa was an emergent and the nest was sited well above the tangles and saplings of the adjacent swamp. Similar to a nest described in Peninsular Malaysia ( Myers 1999), our nest was close to a bees’ nest sited within the tree trunk, which had an entrance tunnel two-thirds of the way up. However, the bees were not aggressive and ignored observers, including on the three occasions when we climbed the tree after the nest had been abandoned, suggesting these were sweat bees (F. Lambert pers. comm.), which do not sting.

Upon discovery on 11 March 2013, both adults visited the site silently with nesting material, hovering beside the tree. The nestbuilding process was then observed in a series of two-hour watches between 11 and 29 March ( Fig. 6 ). Long, tangled fibres (including vines) were draped over the base of some of the Pandanus leaves, near its centre. The birds generally visited the nest singly, bringing one piece of material to the top or side of the tangle. On visits to the roof of the nest, the bird generally wedged its bill into the top of the tangle, rapidly shaking its head to affix the fibre, which was left to hang freely over either side. The chamber was formed once a large number of fibres had been draped over the Pandanus leaves. When visiting the side of the nest, the bird would integrate some material and then grab a previously placed piece emanating from the tangle and push this material inwards, shaking its head to affix the piece to the back wall of the nest, while flaring its tail. As the nest formed, the main nestbuilding activity shifted from the exterior to the chamber. Material was added to the roof during nine of 24 observed visits between 07.00 and 09.00 h

Banded Broadbill nest visitation

Time

on 14 March, five of 28 visits between 07.00 h and 09.00 h on 16 March, and one of 66 visits between 07.00 and 09.00 h on 18 March; all other visits brought material to the sides of the nest or the chamber, which was not well formed on 14 March, but neat and recognisable by 16 March. To work on the chamber, a bird would enter, turn around so that it was facing outwards, then reach down or sideways to grab the end of a free fibre, and pull it inwards. This was often repeated several times during each visit. By the time the chamber was well formed, the base of the nest consisted of a large wad of fibres curling from the sides of the nest inwards. The nestbuilding techniques described here are generally consistent with those reported for Black-and-red Cymbirhynchus macrorhynchos and Dusky Broadbills ( Zubkova 2017).

Division of labour between the sexes was not closely observed because sexing this species at a distance is difficult. Occasionally, while a bird was working on the nest the other member of the pair would join it. Once, on 18 March, one bird sang as it clung to the outside of the nest near the chamber.

On 29 March, one bird stayed in the nest for 1.8 hours during the watch and was still present when we departed at the end of the day. We observed relatively little activity in the two hours beforehand—all visits involved the adult visiting the chamber for a brief period. We interpreted this to signify the presence of eggs and that incubation had begun. It is possible that incubation started before this: Banded Broadbill sometimes continues nest construction after incubation has begun ( Wells 2007). As with incubating Black-and-yellow Broadbills, we could sometimes observe the adult’s blue bill in the nest entrance ( Myers 1999 specifically did not see this). We observed several incubation bouts on 30 March, but during our watches over the next few days, all activity ceased. There was no sign of activity when we collected the nest on 9 April, 2.5 weeks after the earliest possible start of incubation and well before any nestlings would have fledged.

Videos of this nest being constructed can be seen at ML catalogue numbers 479337, 479428–438, 479527–544, 479590, 479998, 480004 and 480006. ML 479590 shows nestbuilding behaviour by both pair members, including an instance in which the male became tangled on a vine and had to struggle for 50 seconds to get free.

Figures

Figure 1. Map of the topography of our study area showing sightings of Black-and-yellow Eurylaimus ochromalus (blue) and Banded Broadbills E. javanicus (maroon) from both visits. Each point represents a sighting. Variation in point size and shape is an artefact of 3D plotting. This map demonstrates that Banded Broadbills occurred at a much-reduced density in the study area compared to Black-and-yellow Broadbills. Grey lines represent trails, the brown line represents a water pipeline, and the blue line represents the Tawau River. 3D map courtesy of JAXA (2015).

Figure 5. Banded Broadbill Eurylaimus javanicus nest during late construction, with an adult exiting at the lower left (© Kayleigh Chalkowski). Inset: close-up of the nest chamber after the nest was abandoned and collected, showing lining material (Eric R. Gulson-Castillo).

Figure 6. Graphical summary of nest visitation by Banded Broadbills Eurylaimus javanicus during nest construction. Y axis = day (day 70 = 11 March) and x axis = time of day. Thin blue lines represent time periods during which nest watches occurred, thicker lines visits by broadbills. The colour of each visit alternates to highlight visits with short intervening breaks, which would otherwise appear to blend into a single line; colour does not represent sex or individual.