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Tuesday, May 30, 2006

Roost of the Great Hornbill

Roost of the Great Hornbill

As far as we know, there is only one Great Hornbill (Buceros bicronis) in Singapore. And this bird is an escapee, probably from the Jurong Bird Park some years ago. For some months now, this bird has paired up with a Rhinoceros Hornbill (B. rhinoceros), another escapee. Two earlier reports (1, 2) give accounts of the activities of these two hornbills prospecting for a nesting cavity in an old albizia tree (Paraserianthes falcataria) around the Eng Neo area. They arrived during most mornings of late February and March 2006, spent half an hour to an hour around the area before leaving. Sometimes they also came during the evenings. Towards late April and May these birds appeared less regularly.

We have always wondered where the birds ended up at night. At last we have part of the answer.

Brian Ng alerted me of a Great Hornbill that regularly arrived every evening around 7.00 to 7.15 pm to spend the night on a branch of a rain tree (Samanea saman) outside his fifth level apartment window around Adam Road. The hornbill stayed all night in this tree but come morning, usually around 6.45 to 7.00 am, it started moving, stretching its wings and preening before flying towards Bukit Timah Nature Reserve. Or that was what Brian thought.

But I think it flew to nearby Eng Neo where it met up with the Rhinoceros Hornbill.

The Great was always alone at the roost. And Brian never saw the presence of the Rhinoceros. Now where can the Rhinoceros be roosting at night?

Towards the end of April onwards the bird visited less regularly, coinciding with its irregular visits to the Eng Neo area. Brian has since confirmed (30th May 2006) that "The Great hasn't returned... in the past weeks..."

Thanks Brian for the alert. Image by Chan Yoke Meng.

Brian’s video can be viewed here.


Sunday, May 28, 2006

Great and Rhinoceros Hornbills: More images

Great and Rhinoceros Hornbills: More images

The courtship behaviour of a Great (Buceros bicronis) and a Rhinoceros Hornbill (B. rhinoceros), both female, at Eng Neo has already been told. However, through the generosity of Meng and Melinda Chan, we are able to showcase here more of what actually happened around the old albizia tree (Paraserianthes falcataria). The pair would meet in the morning and/or evening and the Great (above right, taking on the role of a male) would always check on the cavity. "He" would then fly back to join the Rhinoceros on a nearby branch and delicately fed the latter with a fig. This is the standard courtship ritual. Possibly, this was to reassure her that "he" would keep on feeding her should she be sealed up in the cavity during egg incubation and after (should this happen). Only then would the Rhinoceros fly off to check the potential nest cavity. In the image below you can see a Greater Racket-tailed Drongo (Dicrurus paradisus) harassing the Rhinoceros. There was always a pair, probably breeding nearby, that followed the hornbills around.
The image on the left shows the Rhinoceros, with her head inside the cavity, checking the interior. The Great is perching on the tree trunk below, waiting for her decision.

The pair has been visiting the tree during February to May, as this is supposed to be the breeding period. There is a report of someone seeing the Rhinoceros entering the cavity, to move out soon after. But there has not been any attempt of the Rhinoceros sealing herself inside the cavity. This would be a distinct possibility, considering that both are females. And a female bird would only enter the cavity and seal herself in after copulation.

Such aberrant behaviour probably arises out of desperation. After all, there is only one of each bird in Singapore, both escapees. And they have come together out of loneliness.

Text by YC, images by Meng and Melinda Chan.


Friday, May 26, 2006

Myna-horse relationship

Myna-horse relationship

We are used to seeing mynas hovering around grasscutters or even garbage disposal people. But to see one around a horse? Or chasing the horse when it gallops around the course? Well, Leykun had such an experience, as seen in a letter written on 12th April 2006:

“I was at the Saddle Club recently to practise photography.

“The Common Myna ( Acridotheres tristis) was seen hopping, chasing and even flying after the horse (picture above). I think it was the horse's butt or smell that attracted the bird. It was very purposeful in its actions as it practically chased the horse for several hundred metres until the horse turned a corner and got out of my sight. I am curious to know what the mynah was going after.”

R. Subaraj has this to say: “Possibly flies or some parasite that were on or around the horse. These could be near the rear end of the horse, causing the myna to follow the horse

“The Jungle Myna (Acridotheres fuscus) of Malaysia and northwards was formerly called the Buffalo Myna as it was often found around water buffalos and cows, picking off the ticks and insects on or around the animal. The Javan Myna has also learnt the value of larger domestic animals pushing up grasshoppers and the like from grassy areas and follow them around. In Singapore, Javan (and Common) Mynas can often be found following lawn mowers, picking up the insects stirred up. Other birds like Cattle Egrets (Bubulcus ibis) do it too.”

Thank you Leykun for the interesting story and image; and Subaraj for your comment.

Wednesday, May 24, 2006

Life around a rotting tree trunk 2: Collared Kingfisher

Life around a rotting tree trunk 2: Collared Kingfisher

A pair of Collared Kingfishers (Todiramphus chloris) was nesting in a cavity found at the central point of a rotting tree trunk in a small piece of secondary growth at Eng Neo. Most of March 2006 the birds were flying in and out of the nest. Sometimes the arrival would be accompanied by the shrill cries of the bird. At other times the bird would fly in silently.

The hungry nestlings needed to be fed regularly and the parents worked hard bringing them food. There would always be some invertebrates like a centipede or a grasshopper. The birds would stop over at a nearby tree, checking to see whether it was safe to proceed, before flying to the nest. Initially, it entered the cavity to pass on the food but later it just stopped at the entrance. Sometimes both parent birds approached the cavity at the same time. In such cases one would veer off and wait its turn. There had also been a few cases when the morsel brought to the nest was not accepted by the nestlings (see above). In such cases the parent bird flew off to a nearby perch to consume it.

At the upper end of the trunk was another cavity. Here, a pair of Long-tailed Parakeets (Psittacula longicauda) initially took occupancy. The presence of the parakeets nesting above caused no problems to the kingfishers. Both species coexisted peacefully. However, when the hornbills were around the rotting trunk, which was not often, the kingfishers as well as the parakeets were invariably frightened away.

Text by YC; images by Meng and Melinda Chan (Great Hornbill, bottom) and YC (the rest).


Tuesday, May 23, 2006

Nest raiding

Nest raiding

April 22nd was Earth Day. It was quite busy for Timothy Pwee in many ways. In the morning around 9.30am, one of the Nature Society (Singapore)'s Education Group volunteers, Hui Ping, spotted an eggshell with a fully developed embryo on the grass in the Palm Valley of the Singapore Botanic Gardens. Together with Goh Si Guim, Tim went to take a look. They found several clusters of light blue eggshell fragments around one of the palms. There was one with a fully developed embryo totally out of the shell.

As Tim narrates: “Because the eggshell had cracks radiating from more than one spot, we suspected that the egg had been attacked rather than just dropped from the nest. Another almost complete shell on the other side of the palm appeared to be around one and a half times larger. This larger eggshell did not have speckling. Wang Luan Keng suggested that this shell belonged to the Black-naped Oriole (Oriolus chinensis).”Si Guim continues: “Besides the shattered egg and the spilled embryo of an incompletely developed bird, there were other empty shells around the tree. All were empty. They could be empty shells ejected from the nest(s) above, meaning that the chick had hatched out and fledge. Or the eggs could have fallen and the content decayed some time ago.

“Please note the markings on these two shells (image above). The one on the right does not have brown specks, suggesting different species of birds nesting among the many woody leaf bases on one palm tree. There were many Asian Glossy Starling (Aplonis panayensis) visiting these palms.

“Would forensic birding reveal how these eggs got onto the ground? Were the eggs cracked by raiders or did they break up on impact with the ground i.e. whether they were ejected by parasitic birds or the nest were raided by other birds.

“In the 90s, while exploring the still untouched Bidadari Cementery (Muslim side), I encountered an oriole raiding the nest of other birds. Egg yolk was seen dripping from the branches. I also had a close encounter with the Changeable Hawk-eagle (Spizaetus cirrhatus), now that I recall those nostalgic moments."

R. Subaraj has this to say: "We know that crows raid nests of birds and consume the eggs and chicks. However, I have not heard of orioles doing so too! We must not rule out the Plantain Squirrel as being another potential culprit (especially at the Singapore Botanic Gardens). However, we need documentation to prove whether they simply are destructive or if they actually feed on the eggs.

Input by Timothy Pwee and Goh Si Guim, ID by Wang Luan Keng. Top image by Tim, the rest by Si Guim.

You can view Tim's posting here.

Monday, May 22, 2006

Baya Weavers

Baya Weavers

In Singapore, Baya Weavers (Ploceus philippinus) build their nests in colonies of 20-30, preferring coconut palms or low trees. The nest is expertly weaved from long thin strands of leaf blades that can come from the Guinea grass (Panicum maximum), strips of palm fronds or other tough fibres. A completed nest looks like an upside down flask with a downward pointing entrance chute. Within the swollen portion is the nesting area.

The nest has been described as: “a stocking hung by the toe, the heel enlarged to receive the eggs, while the entrance and exit are made through the leg.”

The nest hangs on a long thin structure (up to a metre long) tightly woven with grass leaves, swinging freely in the wind. This ensures that it is not easily accessible to potential predators, either from above or from neighbouring branches. Thus they are attached to the terminal of palm fronds or from the ends of branches. The birds recycle old nests, repairing any damage before reusing them. This can be easily detected by the colour of the fresh and dried grass blades.

The male bird builds the nest half way after which he tries to seduce the female by his courtship displays. If the female is interested, she will examine the uncompleted nest, after which he will complete building it or both will work together.

Sometimes the birds may bring in lumps of wet clay that are stuck to the interior wall of the nest.

Once the female lays her eggs, the male will move on and build another nest, leaving the female totally to herself to incubate the eggs and raise the chicks. However, there are reports that this may not always be so - males have been observed bringing insects for the nestlings.

Text by YC and images by KC Tsang.

R. Subaraj has this to add: Have you heard the story about the female Baya Weaver snipping off the connecting cord if not satisfied after inspection, so the male has to start from scratch? Do you know if this is true for sure.

An excellent account of the nesting behaviour of Baya Weavers by Graeme Guy of the Nature Photographic Society (Singapore) can be viewed here.

Saturday, May 20, 2006

Nesting of Scarlet-backed Flowerpeckers

Nesting of Scarlet-backed Flowerpeckers

Thanks to a lead by Morten Strange, I was able to record the nesting of a pair of Scarlet-backed Flowerpeckers (Dicaeum cruentatum) and the antics of the two nestlings during April this year.

The nest was an oval pouch woven from grass blades, plant fibres and narrow dried leaves. There was a large opening near the upper end. The inner surface was comfortably lined with white plant fibres, probably floss from the fruits of the kapok tree (Ceiba pentandra). The entire structure was firmly attached to a slender outer branch of an Horsfieldia tree whose numerous flower buds were about to burst into blooms. The nest hanged between the two ranks of large leaves that provided shade from the rain and sun.

Peeping out of the large opening were two large nestlings, with darkish heads and prominently large orange beaks. The parent bird was around somewhere, tick-tick-ticking all the time. Whenever I imitated the sound, the two nestlings immediately opened their beaks to expose the reddish inner lining of the buccal area.

I managed to observe only the female bird feeding the nestlings, bringing them green mistletoe fruits that the babies eagerly gobbled. I was told by Morten that the male bird was extremely shy, not wanting to approach the nest whenever there was someone around. This was not so with the female bird, who fed the nestlings at the rate of once every few minutes, even when I was below the tree. And Morten detected a distinct difference in the calls of the two sexes.

The parent birds regularly removed large faecal sacs that were packed with green mistletoe seeds. Apparently such a service was not efficient. When a parent bird removed the sac from one nestling, the other simply turned round, pointed its posterior towards the entrance and started to excrete the mucous-covered seeds one by one.

Checking the ground below, I was surprised to find masses of mistletoe seeds coated with mucilage lying on the ground.

The nestlings had since fledged, leaving the empty nest hanging from the branch between the rows of leaves. However, a few days later the empty nest disappeared.Text and images by YC.


Thursday, May 18, 2006

Life around a rotting tree trunk 1: Introduction

Life around a rotting tree trunk 1: Introduction

The location: A small piece of wasteland around Eng Neo bordering the Pan Island Expressway on one side and a sprawling low-rise housing apartments on the other.

The vegetation: A young secondary growth dominated by clumps of palms and bamboos overgrown with mainly exotic weeds. A few scattered emergent old albizia (Paraserianthes falcataria) trees.

The cast of characters: Hill Myna (Gracula religiosa), Javan Myna (Acridotheres javanicus), Collared Kingfisher (Todiramphus chloris), Dollarbird (Eurystomus orientalis), Greater Racket-tailed Drongo (Dicrurus paradisus) and Long-tailed Parakeet (Psittacula longicauda), Rainbow Lorikeet (Trichoglossus haematodus), among others.

The attraction of the area: The presence of a few tall and old albizia trees. These trees provide excellent perches for birds, perches where they can get a bird’s eye view of the surrounding area. These old trees, as well as at least one dead and semi-rotting tree trunk are full of cavities, natural as well as otherwise, that many of these birds nest in. Also, the overgrown vegetation is rich in invertebrate fauna, besides providing fruits, like melastoma (Melastome malabathricum) and white-leafed fig (Ficus grossularioides).

The focal point: A rotting albizia trunk that is infested with termites. Half way up the trunk is a number of cavities, with more at the top.

This rotting trunk is the focal point of many birds during the early morning and late evening. A pair of Collared Kingfishers was nesting in the cavity around the centre of the trunk while the upper cavities were inhabited, at different times, by Long-tailed Parakeets and Dollarbirds, among others.

With these different species congregating around this single rotting tree trunk, it is inevitable that conflicts will occur. And occurred they did. In subsequent postings we will bring to you the various dramas that unfolded in this very interesting area, small as it is, in urban Singapore.

PS: This is also the area where a pair of Great (Buceros bicronis) and Rhinoceros Hornbills (B. rhinoceros) was prospecting a potential nesting hole in a living albizia tree. But that is a story already told.

Thanks to Ng Bee Choo and Eng Tow who introduced me to the site. Text and images by YC, except Great Hornbill image by Meng and Melinda Chan.


Wednesday, May 17, 2006

Tingfang and her Olive-backed Sunbirds

Tingfang and her Olive-backed Sunbirds

Tingfang, an undergraduate of the National Technological University, found traces of plant materials around her clothes pegs one day in March 2006.

The very next day when she returned from lectures, she spied a pair of Olive-backed Sunbirds (Nectarinia jugularis) around. The pair continued building their nest every morning from about 7am and “.. their sharp yet sweet chirps served as my second alarm clock. After a week, it looks more like a nest... I have seen how the birdies worked their ass… or probably their beaks off to get this up… now I have a worry - will the cleaner clear it away?”

“After completing the nest, the birds flew in and out of the nest. Sometimes they made a lot of noise.. .. (hmm.. wondering what they are doing inside.. HmmMmm.. *roll eyes, drum fingers*).. can’t get too near to the nest else they would fly away… usually I could get slightly nearer during the night though.”

At night there would always be one bird in the nest, which she presumed to be the female. On12th April she found two eggs inside the nest. While the female was incubating the eggs, the male visited and brought food for her. He would always be “hopping around.” Seven days later, she noticed the male “suddenly became very noisy” and both birds started chirping. There in the nest was a “wormy thing hatched out from the egg... an orange wormy like thingy.” It was a blind and naked nestling. The other egg hatched the very next day.

The female bird stayed in the nest for most of the next two days while the male was busy foraging for food. By the third day both birds were busy looking for food to feed the nestlings.

Although blind at birth, the nestlings opened their beaks wide at the slightest noise or vibration, expecting food from the parents. By age five they had their eyes opened. Feathers developed around the ninth day. By day 13 the nestlings had grown too big for the nest and a side opening appeared.

Fifteen days after hatching Tingfang returned to her unit to find the nestlings gone. They must have fledged. But the nest was also gone. Only the peg and traces of nesting materials remained. Thinking that the nest with the nestlings inside must have fallen, she panicked and looked frantically around in the units below.

Naturally Tingfang felt sad and empty inside. Who wouldn’t? She had been keeping an eye on the birds for weeks, peeping at them to see their progress. And now, they were gone.

Our bird specialist R. Subaraj is of the opinion that the nestlings must have been taken, nest and all, by some predator bird, as this was a time when their presence was conspicuous.

Thank you Tingfang for agreeing to share your account and images with us; and to Goh Hanlin for alerting us to her blog.

You can also log in to her blog for a more personal account.


Tuesday, May 16, 2006

Nesting of Black-naped Oriole

Nesting of Black-naped Oriole

The Black-naped Oriole (Oriolus chinensis) is a very distinctive bird of gardens and parks. Its bright yellow plumage and black nape make it easy to recognise. Its loud and fluty whistle is similarly distinctive. It is a common resident as well as a winter visitor.

The nest is a neat pouch-like structure made up of plant materials like thin pliable stems, roots, grass blades, slender twigs and fibres. These are intricately weaved together into a nest with parts of the rim firmly attached round slender supporting branches high up the tree. There are usually two bluish-white eggs covered with brown spots. It has been reported that the female is the one actively building the nest. In some species the male merely sits nearby, encouraging the female along. But we need to confirm such behaviour in this species.

Cheong Weng Chun came across such a nest in Taman Wetland Putrajaya situated north of the Malaysian capital city of Kuala Lumpur on 5th March 2006.

There were two nestlings in the nest. This was the first time he actually saw the successful hatching of the eggs, his earlier two encounters were failures. Eight days later he saw the two nestlings grown into cute chicks ready to fledge. The very next day both young birds made their maiden flights. He spotted one on a tree some distance from the nest, with the parents feeding it regularly. “Where's the other one?” he wondered.

Text and images by Cheong Weng Chun.


Sunday, May 14, 2006

Courtship of Dollarbirds 2: What the eyes cannot see

Courtship of Dollarbirds 2: What the eyes cannot see

An earlier posting by Meng and Melinda Chan describes the courtship and mating of the Dollarbirds with images to match. Here, another photographer, Allan Teo, has this fascinating story to tell, with photographic evidence as well. Allen describes how he detected the mating of these birds while a pair was spiraling downwards. Without the aid of his camera, he would have thought that the birde were in play or in a fight. Thus he titles his account, "What the eyes cannot see” to stress the usefulness of the camera in bird behaviour study:

“The human eye can only catch motion to a certain extent. We need the help of cameras to see what is actually happening. To the naked eye, a pair of Dollarbirds seems to be falling off a tree branch and rotating on the way down like leaves. You may think they are fighting but look closer with the camera and you will find out something very different.

“One bird grabs the other by the neck as they rotate. They then turn around and face outwards with their backsides attached and mate.

"When they were near the ground, I am guessing less then 2 metres, they flew apart before they hit the ground.

“The action takes place in split seconds and the camera can capture it. Photography provides another valuable insight into intelligent animal behaviour.”

How true, Allan, how true! I have always believe that images help provide quality bird watching. You can always examine the images at your leisure and detect details that you miss when viewing with the binoculars. We are happy to see that traditional birders are now taking up photography, learning digiscoping and even taking up videoscoping. In fact Ashley Ng, our local digiscoping guru and founder of "pigeon-holes", recently gave a talk on digiscoping to the Nature Society (Singapore), invited by Lim Kim Chuah on behalf of the Bird Group. YC

Thank you Allan for sharing your images (below) and your viewpoint. Top image by YC.


Saturday, May 13, 2006

White-bellied Fish-eagle fishing a rat

White-bellied Fish-eagle fishing a rat

Have you ever seen a White-bellied Fish-eagle (Haliaeetus leucogaster) fishing a rat off the sea?

Wong1979, a member of Club Snap, was at the Changi boardwalk in April when he saw some eagles soaring above the sea. Thinking that these birds must be looking out for fish, he had a surprise of his life when he noticed that the ‘fish’ one of these eagles caught had a tail. Well, fish have tails that are rather flattish and broad, not long thin tails. Typically Singaporean, he muttered, “Fish got tail, meh?” He took another and closer look and realized that the prey was definitely not a fish. A monitor lizard? Or some sea creature? The images he captured no doubt helped him to identify the prey as a rat.

Now how did the rat ended up swimming in the sea off Changi? It seems that the boardwalk harbour rats below. Apparently there must be an abundance of food for these rats when the tide is low. He did a google search and found out that rats can and do swim for up to half a mile out into the sea.

Up in the air the juvenile eagle had difficulties keeping its catch. Another eagle spotted an opportunity for an easy meal and tried to grab it from the juvenile.

Thanks to Kevin Lam who alerted me on the posting in ClubSnap, we have an interesting account here. Kevin’s has also posted his version of the rat-catching eagle.

We had out bird specialist, R. Subaraj to look at the images and he ID it as a possible juvenile White-bellied Fish-Eagles. Subaraj says that these eagles are known to take anything swimming in open water. Besides fish, they are also known to take sea snakes and turtles. A rat swimming should be no exception.

Thanks to Wong1979 for permission to re-post his account and to use his image; to Kevin for alerting us and Subaraj for his ID and comment. White-bellied Fish-eagle is now known as White-bellied Sea Eagle.


Friday, May 12, 2006

Courtship of Dollarbirds 1: What the eyes can see

Courtship of Dollarbirds 1: What the eyes can see

Dollarbirds (Eurystomus orientalis) are rollers. The name comes from the fact that these birds exhibit aerial acrobatic flights during courtship. They love to make swoops, rolls and turns, often flying straight up and suddenly tumbling down with a rolling motion. Such flying acrobat is usually repeated several times.

The courting pair spends much time sitting close together on a branch high up in a tall tree. They may indulge in allopreening, chatting and courtship feeding. In courtship feeding, the male offers an insect to the female before she will allow him to mount her. Otherwise she will roughly rebuff his advances. Some ornithologists believe that such courtship feeding will fortify the female bird with extra food just before egg laying. Whatever the reason, such feeding goes on throughout the breeding cycle and even after the nestlings have fledged.

Once mating occurs, egg laying will follow. Dollarbirds nest in tree cavities, often an old woodpecker or barbet holes in dead or living tree.

Meng and Melinda Chan were privy to the courtship behaviour of a pair of Dollarbirds last year at Lim Chu Kang. They managed to capture these excellent images of the final mating stages as shown below.

In the next posting we will give you details of another aspect of courtship and mating of these Dollarbirds by another photographer, Allan Teo.


Wednesday, May 10, 2006

White-crested Laughingthrush and bananas

White-crested Laughingthrush and bananas

"We first noticed, or actually heard, these White-crested Laughingthrushes (Garrulax leucolophus) about two years ago. Usually we only see these birds after a heavy downpour. They will come to our frangipani trees (Plumeria spp.) and take turns to forage on the ground. Usually about four to six each time, but once we saw a flock of about nine.

"About a year ago when our variegated banana was fruiting, we noticed them coming for the ripe fruits. However, the funny thing was that they did not eat the bananas while they were still on the bunch. One or two birds would work at getting a ripe fruit to fall to the ground and only then did they take turns to feed.

"These last months they had been coming almost every morning and sometimes, throughout the day. They were more active after a heavy rain and would feed on the ground. Can it be that the rain water forces more worms and bugs out of the ground?

"Another bird we saw (or heard) during the last few months was the Black-crowned Night Heron (Nycticorax nycticorax). When there's lots of rain, the field next to our house turns into a little pond. The night herons will then come in the evening and feed (or hunt) here. We also see the Chinese Pond Heron (Ardeola bacchus) and once in awhile, the Purple Heron (Ardea purpurea).

Victor Lee"

Thanks, Victor, for the account and Johnny Wee for the image.


Monday, May 08, 2006

Egg-dumping by Asian Koels

Egg-dumping by Asian Koels

Egg-dumping is the term used by birders to refer to nest parasitism. This is where a bird lays its eggs in the nest of other birds. It can be a bird of the same species (intraspecific parasitism) or of another species (interspecific parasitism). The former is fairly widespread but seldom noticed. However, this can be detected when there are two eggs seen in a day as few birds lay more than one a day. The latter is seen in the Asian Koel (Eudynamys scolopacea) where the koel lays its eggs in the nests of other birds. This is because the koel never builds its own nest.

In Singapore these koels parasitise the nests of House Crows (Corvus splendens) mainly. We had a number of earlier postings by Angie Ng (1, 2, 3, 4, 5) and by Hung Bun Tang (1, 2, 3). Below are some engaging discussions on the subject.

Ong Kiem Sian reported that she saw a cuckoo nesting in a fantail nest. The female cuckoo pecked the egg of the fantail and immediately deposited her egg in the nest. This was completed within a few seconds when the host was not around. She wondered if the cuckoos were desperate and cannot find a host nest, would they then become aggressive, like the koels reported in the postings? She added: “And if the female bird still cannot find and cannot tahan (ie desperate to lay her egg), maybe she will drop her egg on to the ground.”

Yap Kim Fatt countered: “I would have thought the koel chabohs (Hokkien for females) would deposit their eggs in the crow's nest by stealth rather than by the gangster-ish method as witnessed by Angie Ng (see links above). I would expect a sort of a hit-and-run ova-parturition when the adult crows are not around the nests.”

Jeremy Lee is of the opinion that “If they are nest parasites, I believe they would have to evolve a quick hit-and-run method of depositing the egg in the nest. I have seen documentaries on TV showing cuckoos caught in the act. And it is surprisingly quick to drop the eggs in the nest.”

At the talk in the National Library by Prof NS Sodhi and Ilsa Sharp to launch their book, Winged Invaders – Pest Birds of the Asian Pacific (Singapore: SNP References, 2006) on 10th March 2006, I nearly got my answer to the above. It would appear that the male Asian Koel will seek out an active House Crow’s nest after which he will call out for his mate. Once the female koel appears, the male will approach the crow’s nest whereby the incubating crow will immediately chase it away. At that split second, the female koel will sneak into the nest and lay her egg. The female will then call to signal to her mate that the mission has been accomplished.

But I was unable to elicit a direct response from Prof Sodhi on whether the female koel will drop her egg on the ground if she is not able to immediately find a nest to lay her egg. He believes that in all probability the crow will leave its nest to chase off the male koel, giving the female an opportunity to lay her egg.

Geoffrey Davison has this to say about fertilisation and egg laying: “I had a look at what few books I have at home, but didn't find anything specific on the time taken from fertilisation of the ovum to laying of the egg by birds. But for all birds, fertilisation has to take place at the top end of the oviduct, before the fertilised ovum is surrounded by albumen, two membranes, and the shell. Since eggs of poultry and many other birds are laid at about one-day intervals, this implies about 24 hours for the egg to proceed down the oviduct.

“Smaller birds lay eggs at shorter intervals, but seldom less than 15 hours or so, and big birds like ostriches would lay eggs at intervals of several days - again, that implies several days for each egg to travel down the oviduct being wrapped in albumen, membranes and shell after fertilisation.

“...It's also possible that copulation is performed shortly before the laying of an egg that was fertilised by an earlier copulation.”

Input by Ong Kiem Sian, Yap Kim Fatt, Jeremy Lee, Prof NS Sodhi and YC; additional comment by Geoffrey Davison; and images of a female Asian Koel sneaking into the nest of the House Crow by YC

Saturday, May 06, 2006

Homosexuality in birds

Homosexuality in birds

An earlier posting on a pair of hornbills of different species, both females, prospecting for a nesting site, has raised the question of homosexuality among birds. But how aware are local birders of such behaviour among our feathered friends? Not much, I am afraid. But homosexuality among birds is a common phenomenon.

Thanks to Lin Yangchen who made an online search and alerted us of the presence of such literature, I have managed to read a few of such reports.

Many species of birds lack sexual dimorphism. Thus we cannot differentiate the male from the female. During courtship and any subsequent mating, there is no way to tell whether the two birds are of the same or different sex. However, among birds showing sexual dimorphism, same sex courtship and mating can be obvious.

People have always been aware of homosexuality in captive birds, especially parrots. Such behaviour here can be due to the circumstances of confinement and may not be normal. However, there have been accounts of homosexuality among wild birds.

A pair of male Orange-fronted Parakeets (Aratinga canicularis) was observed to indulge in courtship behaviour in the wild. Ultimately one bird attempted to mount the other. Both birds were collected for scientific examination and found to be adult males.

Homosexual copulation has also been recorded in feral populations of Rock Pigeon (Columba livia) (left), Cattle Egret (Bubulcus ibis) and Common Murre (Uria aalge). Although no cloacal contacts were mentioned in these cases, it was specifically observed in the case of Tree Swallow (Tachycineta bicolor).

The above are instances of homosexuality between birds of the same species. Homosexuality between birds of different species has also been reported. Among Canada Geese (Brania canadensis), unisexual pairings of both males and females are common. What is uncommon was the instance of pairing between a male Giant Canadian Goose (B. canadensis maxima) and a male Snow Goose (Chen hyperborean). As both these birds were tagged and their sex had been determined earlier during handling, there was no question that they were a homosexual pair. The former assumed the female role, followed the Snow Goose everywhere and roosted close to him at night. However, there was no attempt at mating or nest building.

Another case of interspecific homosexuality was between a Brown-headed Cowbird (Molothrus ater) and a House Sparrow (Passer domesticus) (right). The male sparrow mounted a male cowbird, grabbed its head feathers and attempted copulation. This was repeated twice before the former flew to a nearby fence. The cowbird flew to join the sparrow and nudged the latter until it mounted it a few more times. This behaviour continued for 5-8 minutes.

So, our Great Hornbill pairing with a Rhinoceros Hornbill and checking nesting cavities around Eng Neo is not all that strange after all.

Comment by R. Subaraj: Homosexuality - But then again, maybe it is still strange as most of the other cases mentioned involved males, not females.

Brackbill, H (1941). Possible homosexual mating of the Rock Dove. Auk 58:581.
Buchanan OM (1965). Homosexual behavior in wild Orange-fronted Parakeets. Condor 68:399-400.
Griffin, DN (1959) Apparent homosexual behavior between Brown-headed Cowbird and House Sparrow. Auk 76:238-239.
Lombardo, MP, Bosman, RM, Faro, CA, Houtteman, SG & Kluisza, TS (1994). Homosexual copulation by male Tree Swallows. Wilson Bull. 106:555-557.
Starkey, EE (1972). A case of interspecific homosexuality in geese. Auk 89:456-457.


Thursday, May 04, 2006

Loneliness makes strange bedfellows: Great and Rhinoceros Hornbills

Loneliness makes strange bedfellows: Great and Rhinoceros Hornbills

A pair of hornbills comprising a Great (Buceros bicornis) and a Rhinoceros (B. rhinoceros), both females, have been visiting an old albizia tree (Paraserianthes falcataria) around the Eng Neo area from late February to April to check on a cavity as a possible nesting site.

Every morning and sometimes in the evening, the birds would fly to the tree and inspect the cavity. The Great Hornbill plays the role of a male, trying to lure the Rhinoceros to the cavity by placing food inside. It then flies to the nearby tree to join the Rhinoceros and sometimes feed the latter as part of their courtship ritual. Once in a while the Rhinoceros would respond to the Great’s urging and fly to the cavity to inspect it.
The Great has also been observed to peck hard on the periphery of the cavity in an effort to enlarge the opening.

After some time spent outside the cavity, both birds would fly around, to alight on the yellow flame (Peltophorum pterocarpum) and other trees around the area. There, the pair would stay close together for up to half an hour or so. The Great Hornbill, a probable escapee from Jurong Bird Park, has a metal tag on her right leg. The pair are obviously used to people as they appear tame.

This pair has been seen in Hindehede Quarry prospecting for a potential nesting cavity.

Ng Bee Choo has this to say: "A pair of Great Hornbills died in Sentosa island a number of years ago. This Great Hornbill must be very desperate. Morten Strange has seen it once in the Singapore Botanic Gardens, checking a nesting hole. Both hornbills belong to the genus Buceros. In Thailand, according to Dr Pilai Poonswad, these two hornbills mated and produced a hybrid. In the above case both birds are females. They have paired up for company… however, if they try to mate, this must be a case of lesbian birds. Must be recorded as a case study of birds in desperation."

Top image (Great left, Rhinoceros right) and bottom of Great inspecting cavity by YC.


Tuesday, May 02, 2006

How birds handle the larger ceram palm fruits

How birds handle the larger ceram palm fruits

In an earlier posting it was mentioned that Asian Glossy Starlings (Aplonis panayensis) swallowed the fruits of Alexandra palm (Archontophoenix alexandrae) and a little while later regurgitated the large seeds. In subsequent observations I noticed that other starlings did not always swallow the fruits followed by regurgitating the seeds. They just pecked at the thin pulp surrounding the seeds, leaving the fruits on the inflorescence branch with patches of skin removed. It may be possible that when the fruits are ripe and the pulp soft, the birds will swallow the fruits whole. Short of conducting experiments with caged birds, we may not know when the birds swallow and when they just peck at the pulp.

The fruits of my ceram palms (Rhopaloblaste ceramica) are now ripening and I had the opportunity to observe a flock of starlings feasting on the fruits. These fruits are larger than the Alexandra palm, each about 35 x 20 mm as opposed to 12 x 10 mm fruits of the latter. The pulp of both seeds is thin, less than 2 mm thick. For a bird the size of the starling, it is understandable that it merely pecks off pieces of the pulp.

Yellow-vented Bulbul (Pycnonotus goiavier), about the size of a starling, similarly pecks on the pulp of ripe ceram fruits, without dislodging them from their inflorescence branch. Another bird that had been observed eating these fruits was the blue-crowned hanging parrot (Loriculus galgulus). As with the other birds mentioned earlier, it merely bit off pieces of the pulp.

Along my driveway below these ceram palms, I find seeds of the Alexandra and MacArthur palms (Ptychosperma macarthurii) totally devoid of the pulp. Obviously they have been regurgitated by birds that also feed on the ceram fruits. I know that the starling regurgitate the former seeds but I have no proof that any bird regurgitates seeds of the latter. Can it also be the starling? It would be interesting to find out!

Asian Koel (Eudynamys scolopacea) is reputed to be able to swallow seeds larger that 18 mm diameter but I have yet to observe this bird eating these fruits that is 2 mm larger in diameter, besides being 35 mm long. No doubt it would be an interesting observation.

It should be noted that these birds do not assist in the dispersal of the seeds of this palm as they merely fall on the ground below the palm. As the palm is native to the Moluccas where it grows in the rainforest, its dispersal agent is probably not present in Singapore.

Note: scale in mm. Text and images by YC.


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