A few weeks ago I picked up a small, 14 x 14 mm piece of dry, compressed pellet on my driveway. On examining it under the hand lens, I found that it was composed of short pieces of fibres, a few sand grains, pieces of what looked like coloured palm fruit skin and other unidentified materials.

My immediate conclusion was that it must have been regurgitated by a bird perched on an overhanging ceram palm (Rhopaloblaste ceramica) frond.

Could it actually be a pellet regurgitated by a bird? My knowledge of pellets then was confined to those compressed, undigested bones, hairs, feathers, etc that owls and other raptors regularly regurgitate. But then, pellet casting by non-raptors? By insectivorous birds? By frugivorous birds even?

Intrigued, I looked up the literature. Yes, the literature is flooded with reports on pellet casting by raptors. However, there are also a number of reports of pellet casting by birds that regularly consume fish, insects, caterpillars, etc.

Now, why do birds that are not birds of prey need to cast pellets? Fish-eating birds swallow bones that are removed as pellets. Among the contents of these pellets can be found otoliths, those hard inner-ear bones that can help identify the species of fish consumed. Insect-eating birds need to spit out the hairs of caterpillars and the exoskeletons of insects, for example.

When a bird takes in its food, this is normally passed directly down into the stomach. Here, enzymes, acids and mucous are produced and the process of digestion begins. The food is then passed on to the second part of the stomach, the gizzard, where the soluble parts are ground and passed through to the intestines. The indigestible part of the food is compressed into a pellet by the gizzard, thus taking the shape of the gizzard. This pellet will eventually be regurgitated.

Local birders are familiar with pellets regurgitated by raptors. But most are unfamiliar with pellet casting by other birds. But this is a common occurrence in many groups of birds. In fact the International Bird Pellet Study Group listed 18 orders comprising 67 families and 316 species of birds that indulge in pellet casting. And this was as far back as 1979. Birds that cast pellets include crows, cowbirds, grackles, cormorants, grebes, gulls, terns, swallows, sanderlings and rails.

My only encounter with pellet casting was when I tried to photograph a Blue-tailed Bee-eater (Merops philippinus) perched on my neighbour’s TV aerial. The bird suddenly opened its beak and made some sort of retching action. It must have regurgitated a pellet. As the bird eats mainly insects, the pellet must have been made up mainly of insects’ exoskeletons composed on indigestible chitin. Like scats, you can tell what the birds have been eating by examining their pellets.

Now coming back to the pellet I picked up. I am still wondering what bird spitted it out? And whether it was an insect-eater or a fruit-eater?

Text and image by YC, scale in mm.

Latest: After the above was posted, we received a note from Cheong Weng Chun who wrote: “Yes, non-raptors do regurgitate. I only know about this a few months ago when two nature photographers stumbled upon a bee-eater with its beak open wide and suddenly a pellet dropped out. They even sent me a sample of the pellet. However, due to my busy schedule at work and the heat inside my car (yes, I kept it inside my car for a couple of days), it was subsequently smashed accidently. But yes, I did see the exoskeleton of insects especially wing parts.”

We also received from Jianzhong Liu an image of a Blue-tailed Bee-eater regurgitating a pellet, an act he saw a few times and was lucky to get a shot of it. The image is reproduced below.

Thank you Weng Chun and Jianzhong for your feedback.

Seiko Okajima reported an early morning intruder to her house at Opera Estate in February 2006 thus: “My cat brought in this bird to my house early this morning around 1:00am of Feb 3, 2006. This young bird was not harmed and later flew away safely, but lost some feathers taken by my cat. My house is in Opera Estate off Siglap Road. I’ve never seen this kind of bird near my house during the day.”

Our bird specialist, R. Subaraj, has this to say: “The bird in the photos is a Cinnamon Bittern (Ixobrychus cinnamomeus). The species is normally found in wetland areas such as flooded fields and marshland. While a small number are resident in Singapore, it is believed that many occur as migrants from northern Asia. During the passage months, when the birds are undergoing migration, different species of migrants turn up at the strangest places, including buildings and homes, probably due to disorientation caused by the bright lights of urban areas.

“As Opera Estate is a suburban area, quite away from the nearest marshy area, this individual is probably a migrant that was undertaking a nocturnal movement (most migrants travel by night). For future reference, it would be a good idea to house such migrants for the night and release them during daylight at the nearest marshland/wetland area. This will minimise the risk of the bird getting further disorientated by the lights at your estate and allow the bird to feed in suitable habitat to recover from both the distant movement and the cat attack before continuing it’s travels the next night or so.”

Input by Seiko Okajima and R. Subaraj, images by Seiko.

After the above account was posted, Hung Bun Tang sent in the image of a dead Cinnamon Bittern (below) he found near Malcolm Park in the early morning of 9th January this year. He also believes that this species may be more prone to disorientation during nocturnal flights, thus becoming easy victims to attacks by predators. Thanks, Tang.

Once upon a time, there were three species of hornbills present in Singapore. However, due to rapid development and large-scale deforestation, all three species became extinct in the late 19th century.

One species, the Oriental Pied Hornbill (Anthracoceros albirostris convexus), has made a comeback. There are many of this bird in the offshore island of Pulau Ubin. The original nucleus probably arrived years ago from nearby Johor, Malaysia. On mainland Singapore they are also present, probably originating from a pair of escapees. These birds have now established themselves and are actively breeding.

Many sightings have been reported from mainland Singapore during the last few years, from areas around Kent Ridge, Bukit Timah, Sembawang, Seletar, etc. They often visit urban gardens, foraging for fruits like rambutans and figs. In most cases the birds were shy, flying off when approached.

This year alone there have been a number of sightings. In January, Fuhai Heng saw a family group comprising father, mother and a juvenile in Sembawang. In February, Johnny Wee encountered one feasting on rambutan fruits in Yio Chu Kang Gardens. And Angie Ng saw her pair in an angsana tree (Pterocarpus indicus) next to Changi Meridian Hotel. Similarly Goh Si Guim encountered a pair during his nature walk, examining a cavity in a pulai tree (Alstonia sp.). This pair was obviously looking for a sutitable nesting hole. Also in February, Vilma d’Rozario’s colleague Angelia spotted one flying across the Pan Island Expressway, along that stretch between Eng Neo and Bukit Timah exits. James Heng similarly saw a bird in Upper Seletar Reservoir.

Reporting from Binjai Park, Marisa Keller wrote in saying that the bird was commonly seen around her neighbourhood. She first sighted two birds in July 2005, some juveniles on 15th October and three birds on 30th October. Marisa says: “In the 13 years I live here I never saw or heard a Pied Hornbill.”

Our bird specialist R. Subaraj has this to say: “There have been several hornbill sightings, of various species, over the years and from various parts of Singapore. While all are regarded as escapees, we cannot be entirely certain that we do not receive strays from Malaysia. Based on the locations of the above reports, it may be that most were Oriental Pied Hornbills as three have been seen off and on at the Bukit Tinggi/Binjai Park area. These may be part of a feral population that started years ago at Upper Seletar Reservoir. The other possibilities are Great Hornbill (Buceros bicronis) or Rhinoceros Hornbill (B. rhinoceros), as there appears to be one of each at the Bukit Timah Nature Reserve.”

Hornbills are still around in Singapore. So the next time you see a large black and white bird with a large and prominent beak flapping noisily about, chances are that the bird is a hornbill.

Input by Fuhai Heng, Goh Si Guim, James Heng, Vilma D’Rozario, Johnny Wee, Marisa Keller and R Subaraj. Images from top down: YC, Johnny Wee, Fuhai Heng and Marisa Keller.

The following information comes from observations conducted in February 2005 on a nesting pair of Pink-necked Green Pigeons (Treron vernans) in my garden (see 1 and 2). It is reported here to provide conclusion to the series.

Egg incubation took 17 days. The newly hatched nestling was near-naked, sparsely covered with short pin feathers. The two large and prominent eyes were closed. As with the eyes, the large beak was similarly out of proportion to the body. On the second day, more pin feathers sprouted, as well as the beginning of black primary feathers and a few yellow ones. On day three the eyes were opened and on day six the nestling was totally covered with feathers. A day later the nestling was observed to actively preen its feathers and exercising its wings. The nestling was restless, moving around the nest while the parent bird sat quietly still.

As in egg incubation (see 3), the male looked after the nestling during the day and the female during the night. Both parents helped feed the nestling.

As the nestling grew older, it exercised its wings by flapping them, especially when the wind blew through the tree. The nestling fledged at 10 days, leaving the nest to eventually find it way to a nearby mempat tree (Cratoxylum formosum). The male parent was seen sitting beside the fledgling, feeding it whenever the latter begged by pecking its parent’s neck. Sometimes the fledgling used its wing to harassed the parent bird for food. According to the literature the fledgling is fed with regurgitated fruits, not crop milk.

The pair remained on the same branch until evening. The next morning the male bird was still at it side. The female must have left early. By late afternoon the male bird left the fledgling alone before the arrival of the female. Some evenings both parent birds would vocalize, cooing and making rasping sounds as well as flapping their tails. The fledgling would suddenly appear from hiding and all three would fly off. Whether the fledgling was left along during the day or the male was accompanying it, I am unable to say. Similarly I am ot able to say what happened during the night.

With each day the birds would fly further and further away from the nesting area, no doubt until the fledgling totally mastered its ability to fly.

In all, I had been observing these birds for nearly a month, All the time, while the birds were in the nest, I was keeping close watch behind a canvas hide twice a day to record the shift change. Naturally when they all left the scene I was left with an empty feeling – to await the next time a pair nest in the tree again.

Note: Birds’ nests and the birds in them should not be disturbed unnecessarily, otherwise there is always the possibility of the parent birds suddenly abandoning the nestlings.

For a complete account, please see: Wee Y.C. (2005). Forging a closer relationship with Pink-necked Green-pigeons. Nature Watch 13(3): 16-21.

On 10th February 2006, five days before the writing of this entry, my parents noticed movements in our small chiku tree (Manilkara zapota). This tree is no more than 2 metres tall and is right next to the fence that separates my neighbour’s garden from mine.

In my mother’s words: ” An olive bird with a dark ring around its eyes with twigs in its beak was hopping from branch to branch.” There were two birds, identified as a pair of Yellow-vented Bulbul (Pycnonotus goiavier). Within an hour or so, a small cup of twigs came into shape. The bird would often sit in its nest, while arranging and weaving new-found twigs into the cup around it. They were done by the end of the day after repeated returns to the nest with more nesting materials.

The nest was built with a variety of twigs, some coarser, some finer. But what struck me was the unusual white substance that formed part of the cup (see left). Apparently, it was a small piece of fabric that was incorporated into the nest.

The nest was well camouflaged but had only one weakness. It could be viewed easily from the side due to an opening in the chiku tree foliage. As such, the bulbuls, whenever they were at the nest, would often fly off the moment they saw anyone approach from that side.

I also noticed that they entered the nest from various points to avoid detection. One entry was by way of the fence. By landing on the fence that was beside the tree, the birds had easy access to the nest - just two hops away. Another was from the bottom of the foliage, and by hopping from branch to branch, it could reach the nest at the top. Thus the birds would not be flying in from the top and be noticed. This is quite similar to the strategy adopted by the Greater Coucal (Centropus sinensis) that walks till it reaches the nesting site, then fly up, rather than fly in straight.

A day after the nest was completed the birds were rarely there. Whenever they returned, they would bring more materials, to continue touching up the nest. After they were truly satisfied with the nest, they still did not frequent it and were often seen on my neighbour’s roof making alarm calls. This could be because they noticed me watching them.

However, they returned nearer to the nest in the mornings and evenings. Perching on the fence and making excited calls, raising and lowering their heads as they did so.

I have no idea whether these bulbuls would lay eggs as there have been a lot of interference from my immediate neighbour and from my parents who tended the garden, usually resulting in the bulbuls leaving for long periods at a time.

Contributed by Lim Junying with images supplied by him, 15th February 2006.

PS: After 12 days of incubation, the parents failed to return the next day. I assume it was either a bad egg or the egg was taken by a lizard or cat. JY Lim, 25th March 2006.