Eurylaimus ochromalus, Raffles, 1822

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 : 11-15

BLACK-AND-YELLOW BROADBILL Eurylaimus ochromalus

By far the commonest broadbills at our study site. We made spot maps of sightings (compiled in Fig. 1 ) which demonstrate that Black-and-yellow Broadbill occurs at a fairly high density throughout the areas we surveyed, relative to Banded Broadbill E. javanicus with which its home ranges overlapped.

Individuals (in pairs or small groups) often counter-sang in close proximity to other individuals or groups. They interspersed their frequent songs with throaty keowrr calls, which were used during sometimes aggressive confrontational interactions (as in a video JMH made at Sepilok Rainforest Discovery Centre , near Sandakan in north-east Sabah, ML 480277 ). Attempts to understand territoriality by colour-marking three individuals were largely unsuccessful because we only re-sighted birds twice: one on the day following its capture in the same general area; and the other at its nest, 137 m from the mist-nets, several days post-capture .

Despite frequent apparently confrontational behaviour, such as counter-singing, we rarely witnessed aggressive interactions such as chasing. Individuals we observed had a high level of tolerance for others in their territories or in close proximity. Even in areas where birds frequently counter-sang, individuals were often accompanied by several others silently perched nearby and only calling occasionally. In one territory, three adults —a female and two males —often approached together in response to playback and showed no signs of aggression to each other. Once, when only the two males appeared, they duetted after flying back and forth together, searching for the source of the vocalisations. Wells (2007) reported gatherings of up to five birds, but no ‘regular associations larger than pairs or pairs with offspring’.

Although other broadbills sometimes breed cooperatively ( Phillipps 1970, Lambert & Woodcock 1996, Zubkova 2017), we never saw more than two Black-and-yellow Broadbills at or in the general vicinity of nests, except once when two females and an unmarked male briefly perched near an almost constructed nest belonging to a different (colour-marked) male. One of the females entered the nest for a few seconds, but all three birds departed shortly afterwards. Unseen birds sang and called throughout the event, but the colour-marked male did not arrive until 30 minutes later. The unmarked male never came near the nest again, and it is unlikely that he was engaged in cooperation.

Wing displays have been described for this species. These involve stereotypical raising of the wings, usually slightly above the back, accompanied by a slow opening and closing of the flight feathers ( Lambert & Woodcock 1996). We observed such displays in a variety of contexts. Individuals frequently displayed after singing and after arriving in an area in response to playback. However, there were many situations in which a lone bird that had apparently been foraging would open its wings. On several occasions, we observed them spread just one wing at a time, and other times a spread wing was accompanied by a tail wag. When we approached birds along the canopy walkways at the Sepilok Rainforest Discovery Centre, we could hear soft vocalisations associated with these displays (Fig. 2, ML 480226), which were higher pitched and squeakier than similar calls of Banded Broadbills (see below). We also sometimes witnessed gaping displays along with wing displays, during which an individual would open and close its bill in a deliberate fashion without making any sound ( ML 479588, 480299). These displays may be enhanced by the striped pattern of the gape. However, it is sometimes difficult to distinguish these from nondisplay yawning or stretching (e.g. ML 480305). More information on the contexts of these displays would aid our understanding of the species’ social behaviour.

Like Prentice (1988 in Lambert & Woodcock 1996), we observed a copulation following a wing-spreading display, and videoed the entire process ( ML 471162). On 24 July 2012 at 07.58 h, an adult male and female perched on a horizontal branch c. 6 m above ground. As the male flew in, the female spread her wings and opened her bill. The male then performed

Figure 2. Spectrograms of the soft vocalisations made by Eurylaimus broadbills while performing spreadwing displays. In both species the duration of each note was c.0.12–0.2 seconds, given at a rate of 2–3 notes / second. Black-and-yellow Broadbill E. ochromalus calls (top, n = 10 in two bouts) ranged from 1.14 to 1.75 kHz (mean 1.45) and Banded Broadbill E. javanicus calls (above, n = 6 in one bout) from 0.61 to 0.88 kHz (mean 0.73). A set of harmonic notes is visible above the fundamental frequency in both spectrograms.

the same displays. They did not wag their tails, as they did in the display described by Prentice (1988). Following several repetitions by both individuals, they copulated. The male then perched to the left of the female and continued to perform wing displays but the female did not (similar to Prentice 1988). Four seconds later the female briefly pecked the male’s bill while he continued displaying. The male continued displaying his wings until after the female departed a few seconds later.

We observed one active nest (see Fig. 3 ) in late July 2012, and four between 9 March and 22 April 2013. An additional new nest construction attempt was observed briefly on 9 May 2013. The five nests were high in trees (c. 20–35 m above ground). Most were at least partially shaded by a leafed branch or vine, but that in July 2012 was suspended from a brushy vine tangle dangling in the open away from the tree’s trunk, exposing the nest to full sunlight. All of the nests swayed freely in wind. Some nests were concealed, but others were conspicuous. We never noticed bee or wasp hives in the vicinity of nests ( Lambert & Woodcock 1996, Smythies 1999), despite searching for them. The appearance of the nests was consistent with previous descriptions (summarised in Lambert & Woodcock 1996, Bruce 2003, Wells 2007). When incubating, the bird’s blue bill was often visible in the nest entrance (as in Norman 1964), but birds also frequently hunkered down and were invisible inside the chamber.

We inferred that the nest discovered on 12 July 2012 contained eggs because adults spent long periods of time inside it, probably incubating. Two nests in 2013 were discovered during nest construction between 29 March and 2 April. One nest in 2013, discovered on 13 March (when inferred to be in the incubation stage, due to long visits by adults), was predated between 19 and 21 March. Another of the 2013 nests was found completed on 27 February, but no birds were in attendance. Ten days later, we observed visiting adults

Black−and−yellow Broadbill nest visitation

Time

and discovered that incubation had commenced. The broadbills never laid eggs in the two nests that were discovered under construction, instead abandoning them as soon as they were complete. Some birds construct nests without using them (e.g. Verner & Engelsen 1970, Berg et al. 2006), but it is possible that our presence (which did not deter the birds from continuing construction efforts) might have prompted them to delay incubation. One of these nests belonged to a colour-marked individual, and we continued to see this male nearby after the birds stopped visiting it.

Both members of a pair participated in nestbuilding. Addition of material appeared to occur in three distinct parts of the nest: the roof, near the nest’s attachment to the branch; the sides; and the internal chamber, where most attention was focused late in the process. Birds added material with vigorous head-shaking like Banded Broadbills, but they did not appear to pull loose material from the sides inwards to the chamber (see Banded Broadbill account). The chamber was formed from within, often by the birds pressing their head or breast against the walls. Visits with material tended to last 15–100 seconds, with visits by the female generally longer than those by the male. Sex ratio associated with the number of visits made to the nest seemed equal, with both adults working on the sides and chamber, but the roof was predominantly built by the male. Visit length increased as building progressed.

Both adults participated in incubation ( Fig. 4 ). Entries and exits were swift and easily missed, making birds difficult to sex unless the visit was recorded on video and analysed later. Of a sample of 32 videoed visits at one nest during incubation, the female was identified visiting twice as frequently as the male (14 female, seven male, 11 unidentified due to the angle of entrance / exit). Within this small sample of visits, the mean incubation bout also differed between the sexes, with males remaining on average 75 minutes (n = 7) and females 38 minutes (n = 14; the mean duration for birds of unknown sex was 36 minutes, n = 11). When an adult departed, the nest was often unattended for several minutes before the presumed mate arrived; these off-periods were substantially shorter than on-periods, usually less than 15 minutes in duration, although they occasionally lasted>30 minutes to nearly an hour.

Both sexes defended the nest. In 2012, we observed a Prevost’s Squirrel Callosciurus prevostii foraging in a nest tree for 30 minutes, during which period the broadbills were apparently absent. The squirrel eventually came to a vine near the nest whereupon both pair members suddenly appeared and made very fast vertical dives near the squirrel. Although the birds did not appear to make physical contact, the squirrel jumped from the vine and landed in a tree below. We never witnessed nest parasitism, although known broadbill nest parasites (e.g. Indian Cuckoo Cuculus micropterus ) were abundant at the study site.

We occasionally saw broadbills carry triangular green objects (probably leaves) into the nest chamber during incubation. Other broadbills often line their nests with green leaves ( Wells 2007, Zubkova 2017), although Wells (2007) noted that a Black-and-yellow Broadbill nest he inspected lacked them. Once we caught an image on video that could be sexed, and it was the male holding the leaf ( ML 471552; Fig. 3 ).

We did not observe nestlings (or feeding behaviour indicating their presence) at any of the five nests we found. One nest in 2012 was abandoned during incubation; one in 2013 was predated (and visibly torn) during incubation; two in 2013 were abandoned prior to incubation; and one in 2013 was in a tree that came into leaf subsequently, blocking the nest from view (whether it later produced nestlings is unknown). Around six weeks after the nest in 2013 was predated, we observed a pair in the early nestbuilding stages c. 20 m away.

We saw fledglings twice, once each on 16 July 2012 and 20 March 2013. In the latter case, the bird was accompanied by three other birds— one adult of each sex and one of unknown age and sex. Both fledglings matched descriptions in Lambert & Woodcock (1996) and Myers (2009).

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 3. Black-and-yellow Broadbill Eurylaimus ochromalus nest, 2013 (Eric R. Gulson-Castillo). Inset: Black-and-yellow Broadbill holding a green object just before bringing it to its nest, from video ML 471552 (© Brian Magnier)

Figure 4. Graphical summary of nest visitation by Black-and-yellow Broadbills Eurylaimus ochromalus during incubation at one nest in 2013. Y axis = day (where day 68 = 9 March) and x axis = time of day. Thin blue lines represent time periods during which nest watches occurred, thicker lines represent visits by broadbills. Colour of thicker lines represents sex: pink = female, blue = male, dark grey = unsexed. Individuals could not always be sexed due to the angle that they approached the nest; these three colours probably represent just two individuals. When visit breaks are too short to be visible, they are marked with a small green line.