Nearly every evening in early January, from about 6.00 pm, a pair of male Olive-backed Sunbirds (Nectarinia jugularis) (top) would settle down on my neighbour’s bougainvillea bush and spend some free time preening. In between preening they would simply sit tight, stretch their wings and enjoy the scenery. At exactly 7 pm when it was still light, they would suddenly fly off, where to, I do not know. Some days there would only be one bird.

On other days there would also be a pair of lovey-dovey Oriental White-eye (Zosterops palpebrosus) (bottom). I presume this was a pair, as the two birds would often sit close together, sometimes indulging in allopreening.

The Crimson Sunbird (Aethopyga siparaja) sometimes visit the bush but stayed only for a short while, never resting on a branch for more then a few seconds. They are the ones regularly visiting my noni tree (Morinda citrifolia).

These birds, together with Scarlet-backed Flowerpecker (Dicaeum cruentatum) and Brown-throated Sunbird (Anthreptes malacensis) were always around the mistletoe Macrosolen cochinchinensis when this plant was flowering and fruiting. This semi-parasitic plant grows on the branches of a nearby mempat tree (Cratoxylum formosum) that, thankfully have been left alone and not pruned away by the maintenance crew of the National Parks Board. When the mistletoe plants were flowering and fruiting, these birds enjoyed the copious nectar secreted by the flowers and the succulent berry-like fruits.

Being a regular perching bush of these birds that feed on the mistletoes, the bougainvillea obviously shows signs of the presence of their germinating seeds. These can clearly be seen growing on the stems of the bush (see germinating seed, above), no doubt in time to come, will weaken the flowering bush unless they are removed.

PS: About a month after the above piece was written, my neighbour’s bougainvillea bush was heavily trimmed by her gardener. The mempat tree was similarly pruned and most of the mistletoe plants removed, but not completely. I await the return of the birds when the plants grow back to their former glory.

Caterpillars are regularly eaten by birds. However, most birds avoid the noxious ones, especially those that are brightly coloured and hairy. Cuckoos (Cuculidae) specialise on caterpillars as these are their favourite food and they have no hesitation eating even the noxious ones. The arboreal species generally perch motionless on a branch looking for caterpillars. When a one is spotted, the bird grabs it and returns to its perch to eat it. Because caterpillar guts may be filled with indigestible and toxic leaf matters, the bird carefully removes the contents. This is done by biting off one end and gently thrash it against a branch. Once the gut contents are removed, the bird swallows it whole. Sometimes the caterpillar is passed back and forth through the bill to remove the contents. Hairy caterpillars are similarly swiped against a branch, not to remove the hairs, but to empty it of its gut contents. The birds apparently eat the caterpillars together with the hairs, the latter forming a mat in the stomach. These hairs are regularly regurgitated as pellets.

We give below two personal accounts of how two different species of local birds handle large caterpillars.

Robert Teo reported seeing an Oriental Pied Hornbill (Anthracoceros albirostris) in Pulau Ubin that caught a caterpillar of the Atlas Moth (Attacus atlas). This moth is the largest in Southeast Asia and possibly in the world. It’s bluish green caterpillar has a series of dorsal and sub-dorsal spines. The hornbill had the caterpillar in its beak and was vigorously shaking it before finally swallowing it.

Tan Hang Chong tells of another incident: “As I was birding along Lorong Sesuai some years ago, I chanced upon a Crow-billed Drongo (Dicrurus annectans). The bird was perched on a tree at eye level and I had the opportunity to observe it for a long while. What caught my immediately attention was that it had one of the largest tan-coloured caterpillar I had ever seen in its beak! The caterpillar was easily 15 cm long and as thick as my finger.

“The drongo started to move the caterpillar along its beak (ala cartoon characters eating a cob of corn). I initially presumed that the drongo was trying to flatten the caterpillar, the better to swallow it later. Thereafter, the drongo turned the caterpillar around, held it on its end and proceeded to swallow it whole. It surely looked like a most uncomfortable feat as the drongo’s torso was not much longer than the caterpillar!”

Contributed by Robert Teo and Tan Hang Chong, additional input by YC; image of Atlas moth caterpillar by Angie Ng and of hornbill by YC.

The place: near the Pasir Ris MRT Station, Singapore. The time: around 8 am. The date: 22nd December 2005. I noticed this whole assemblage of different species of birds on the grass, some foraging, others just looking around. There were crows, mynas, egrets and rock pigeons. More were continually joining in, especially pigeons and crows. The egrets didn’t really seem to mind and almost seemed oblivious to the 30-40-strong gathering before them.

Could the spot be a designated meeting ground for birds? After all, birds sometimes do communicate and discuss eating places, like Singaporeans. Or could the spot, judging from the seemingly limited interspecies interactions, be just a good spot for forage or rest? If the latter, it is amazing that there is no or little competition or observable territorial behaviour among different bird species!

Text and image by Lim Junying.

Comment by our bird specialist, R. Subaraj: I am glad that you were observant enough to notice this. Most people, including many birdwatchers, would have simply ignored the gathering as it mainly involved common urban species.

Based on the photo and what you have written, I would think that the area is a good feeding site. The Cattle Egrets (Bubulcus ibis) normally hunt insects in fields and the mynas and crows are opportunists who would also catch and eat insects. The patch of grass may be rich in invertebrate life due to some unknown reasons (dampness, freshly cut grass, etc.). As for the pigeons, they may focus on seeds but could be eating invertebrates as well, being highly adaptable.

As for competition, if there is plenty about there should be no problem. However, it may be interesting to study if they are working as a team, in a birdwave of sorts. A birdwave is a gathering of insectivorous bird species that move together to stir up more insects. This is a common occurrence in forests, from the lowlands to the mountains. The more birds involved, the more insects are stirred up and the better chance of finding a buffet, such as a tree of caterpillars.

Does this behaviour occur on the ground and in more open country or urban settings? Should be fun finding out.

Keep at it and nature never fails to amaze!

In an earlier posting it was said that Yellow-vented Bulbul (Pycnonotus goiavier) does not swallow Alexandra palm (Archontophoenix alexandrae) fruits. It pecks on the outer pulp, leaving the fruit on the branch with patches exposing the seed.

With the MacArthur palm (Ptychosperma macarthurii) (above), I have noticed that this bird does swallow the fruits whole. Although I have not seen it regurgitating the seeds, I did find a few patches of faeces with seeds on my driveway. It is possible that the bulbul passed out the seeds?

However, I have been puzzled by the presence of many individual seeds of this palm, cleaned of pulp, scattered along my driveway (left). I do not grow this palm in my garden. These seeds must have been regurgitated by some birds. Can it be the Pink-necked green Pigeon (Treron vernans) that regularly perch on the overhanging ceram palm (Rhopaloblaste ceramica) fronds?

And why does the bulbul swallows fruits of the MacArthur palm but not those of the Alexandra palm? The answer lies in the size of the two seeds. Alexandra palm fruits are nearly round, 12×10 mm, with a single large round seed that is about 9×8 mm in dimension. The flesh is a thin layer of 2-3 mm thick. Although the fruit of the MacArthur palm is of similar size, the seed is very much smaller. It is 10 mm long but only 5 mm broad.

Obviously we have much to learn about the feeding habits of our common birds.

Transverse sections of fruits of MacArthur (left) and Alexandra (right) palms.

Seeds of MacArthur (left) and Alexandra (right) palms.

Scale in mm.
All images by YC.

My Alexandra palms (Archontophoenix alexandrae) are fruiting again. The large bunches of red fruits invariable attract Asian Glossy Starlings (Aplonis panayensis) that are a delight to watch, what with their iridescent dark plumage and bright red eyes. I was pleasantly surprised to observe earlier that these birds swallowed the fruits whole but soon regurgitate the seeds after the pulp had been removed in the gut.

Reviewing my earlier images of koels caught in the act of raiding these fruits, I found that I have evidence that Asian Koels (Eudynamys scolopacea) regularly swallow the fruits (see above) but have yet to actually see them regurgitate the seeds.

Yellow-vented Bulbuls (Pycnonotus goiavier) are similarly attracted to these fruits, but only when the starlings are not around. But these bulbuls apparently have a smaller gape than the above two birds as they are not able to swallow the nearly rounded 10×12 mm fruits. Instead, they peck on the red fruits to remove pieces of the soft outer covering, leaving the fruits with patches exposing the seed surface still attached to the bunch.

Obviously the starling, koel and bulbul are inefficient seed dispersers as far as the Alexandra palm is concerned. Depositing the seeds at the base of the parent palm is not advantageous to the plant at all.

I wonder whether there are any animals that actually disperse these seeds. As an exotic palm introduced from the warmer regions of Eastern Australia, it is very possible that the seed dispersers are absent in Singapore.

Comment by R. Subaraj: It would be interesting to find out if some of our local animals like plantain squirrels, actually help disperse the large seeds of some of our exotic palms.