The Olive-backed Sunbird (Cinnyris jugularis) that was hard at work collecting fibres for weeks from a piece of fabric in front of my house was actually building a nest in the garden of my front neighbour. I did suspect that the bird was building her nest there as she would fly immediately into the compound after collecting a few strands of fibres. But I paid scant attention as these nests are common in urban and suburban gardens, even in the small balcony gardens of high-rise condominiums.

Imagine my surprise and dismay when my neighbour Sheng Lau mentioned to me on 9th February 2008 that the nest was totally destroyed a few days back.

Apparently, five Long-tailed macaque (Macaca fascicularis) descended onto the scene one day and one of the macaques simply ripped the nest from the branch and threw it away. There were two eggs in the nest but it has not been established whether the eggs were eaten by the macaque.

Another failed nesting by a pair of Olive-backed Sunbirds. Failure due to various causes is common (1, 2, 3, 4) . But all is not lost.

I was surprised to see the female bird hard at work continuing collecting fibres from the same tree in front of my house (left). This time she did not fly directly into my front neighbour’s compound. Instead, she flew into the next house, obviously to restart building her nest elsewhere, hopefully in a safer environment. Does this mean that she will be laying more eggs once the nest is rebuilt?

A persistent female sunbird indeed…

On the morning of 7th November 2007, Tan Teo Seng brought me a cutting of a creeper with a Common Tailorbird (Orthotomus sutorius) nest still attached to it. Inside were three damaged eggs.

The nest was attached to a number of aerial roots of the creeper and a single leaf of the climber, an araceous plant. A single dried avocado (Persea americana) leaf was sewn to the leaf of the climber to complete the shell within which the nest was lodged (above left). Copious cobwebs were used in the construction of the nest, as shown in previous posts (1, 2). So good was the camouflage that the gardener did not notice the nest when he trimmed the plants growing along the wall of the porch.

When Teo Seng discovered the gardener’s mistake, he immediately took the nest, still attached to the plant stem and hung it back. There were three small, light bluish eggs covered with various sized chestnut blotches and speckles.

The next day when he examined the nest, he found a small puncture in each of the three eggs. When he handed the nest and contents to me three days later, the openings were large and the eggs empty (left).

A few questions need answers. Did the parent birds returned and punctured the eggs, considering that the nest and eggs were disturbed? Could it be predation? In which case why were the eggs not seriously damaged? Are there any animals capable of causing a small puncture on the egg to extract the contents?

If any reader has an answer, please share with us.

An earlier failed nesting of a pair of tailorbirds was due to the parent birds not feeding the two chicks that eventually died in the nest.

Images by YC.

On 21st December 2007 KC Tsang was birding with Wang Luan Keng at Tuas. This is KC’s report:

“…as I have not gone to that place for quite some time. The place was quite wet, or flooded up to about knee deep in some places, and it was after some heavy rain during the night (above). Knee high gumboots, or wellington boots are required for the exploration of such a terrain.

“Snipes, Savanna Nightjar (Caprimulgus affinis) and Red-wattled Lapwings (Vanellus indicus) are bountiful, however getting a picture of anyone of them is really difficult, and especially if one has to balance oneself in knee deep water, and undulating ground. Here is one Savanna that did not get away (left).

“Having enough of chasing birds for the morning, decided to return back to the car, and pack up for the morning. On the walk back I noticed that there were four eggs in a nest just above the water level. On closer inspection the nest was wet just beneath the eggs (below left).

“So without further-a-do, took some pictures of the eggs, and nest. The nest is hidden somewhere in just above the water (below right).

“Returned the next day to have a look at the nest, everything looks alright with the four eggs still on the nest.

“However on 28th December, two eggs went missing, so we came to the conclusion that a snake might have eaten them. So went about trying to see if we could find a co-operative Snipe who will pose for a portrait shot, no luck there.

“Our final visitation was on 6th January 2008, and to our dismay there were no eggs in the nest. On closer inspection we found them to have also been rolled (?) off the nest, four of them, one broken, and other three intact. So what most probably happened was the first two missing eggs were pushed out of the nest and left submerged under water. And the later two were also then pushed off the nest and left to drown in the water. By the time we came back the place had dried out and thus we were able to see all the eggs on the ground. So on placing them all back into the nest, flies came buzzing around the eggs, which is a bad sign.

“So could it be that the birds had noticed that the first two eggs had failed to develop and decided to remove them from the nest so that it will not affect the other two? The failure of the eggs to develop could also be the result of continuous daily heavy rains, which prevented the eggs developing as a result of insufficient warmth from the sun, or the nest could have been temporarily submerged because of the heavy rainfall, which subsequently killed the eggs.

“According to a knowledgeable birder, a very high percentage of nesting end up in failure.”

Wang Luan Keng has this to add: “KC made an interesting find. It’s unfortunate that the eggs did not hatch. They are really rotten and I have to master enough courage to blow out the contents.

“1. The eggs and clutch size matched the size and description of the Red-wattled Lapwing (above). See also Jonanthan Cheah’s photo (right). KC’s eggs have larger black blotches than Jon’s eggs but I think that is just variation.

“2. According to literature, the nest of the RW Lapwing is an unlined scrape in short grass, soil or sand. The nest Jonanthan found was like that - a scrape on the stoney ground. This is where I am a bit puzzled. The nest that KC found was unlined, formed by a clump of grass folded to form a slight platform, where the eggs sit. Rails and bittern typically do that but the eggs do not match the colours of bittern or rail eggs. I thought it might be common moorhen but the colours are also wrong. It is possible that the Tuas lapwings have adapted to using the grassy patch for nest or a slight possibility that that it is something else.

“3. Many reasons would have caused the failure of the eggs. We know it’s not a predator, which would have eaten the eggs instead of dropping them. KC’s idea that the nest got flooded and the eggs were washed away by the water is possible. Another possibility is that the parents are not experienced or disturbed by humans and somehow dropped the eggs.

“4. KC is right that a high percentage of nests fail in the tropics. Unfortunately, local birders do not follow up on individual nest and do not report nesting records regularly, especially if the nest failed. So we don’t have absolute data.“

Images by KC, except image of egg and chick by Dr Jonathan Cheah Weng Kwong.

“On 26th June 2007, walking along the bund among the mangrove vegetation, I came across two sunbirds flitting among the bushes excitedly. On further observations it was noticed that they were Copper-throated Sunbirds (Leptocoma calcostetha), a male (left top) and a female (left bottom). The female would be perched on a branch while the male would approach her with wings fluttering furiously. Then he would perch right besides her before flying off again.

“However, on this day, I did not realise that there was a nest around the place and walked off looking for subjects to take pictures of.

“The next day I decided to go back to the same place to make further observations. I found the two birds still behaving in a similar fashion. This time I found the nest hanging from a vine and very well camouflaged. Looking into the nest I saw that it was empty, no eggs. I stood around quietly and saw that the female would look into the nest and fly off, then returned and went into the nest - I guess to try it for size. The male would hang around close by observing her every movements.

“On 2nd July I found the female bird inside the nest (right top). She stayed there for a long time before leaving to feed. I peeped into the nest and saw that there were still no eggs. During this period I found the male absent. Only the female was attending to the nest. Can it be because they are nectar feeders, they would find it very hard to feed each other? I may be wrong on this.

“Two days later (4th July) I returned and when the female left the nest, saw two purplish brown eggs (right bottom).

“The 6th July was a very sad day as I found the nest to be missing of the eggs. They could have been predated by a snake as the nest had remained in very good condition. Also, as it was hanging from a vine, anything large and heavy would have torn the nest from the vine. According to a knowledgeable birder, he says that nesting success rate is only about 30 percent. I found incidences like this also happening to Yellow-Vented Bulbul (Pycnonotus goiavier) nests in our garden - overnight, the eggs would disappear into thin air.

“The nest is pear shaped, with an awning over the entrance to protect the female from falling rain? How is it that the male sunbirds would be able to think of this feature?”

K C Tsang, 26th June to 20th July 2007

NOTE: According to Cheke et al. (2001), the nest is a pear-shaped bag with an oval entrance in the top half with an eave. It is made of fine grass, fibre, kapok and hairs, all loosely woven together. There is no ‘beard’ hanging loosely below the nest as in Olive-backed Sunbird (Cinnyris jugularis) (1, 2).

Reference:
Cheke, R. A., Mann, C. F. & Allen, R. (2001). Sunbirds: A guide to the sunbirds, flowerpeckers, spiderhunters and sugarbirds of the world. New Haven & London: Yale University Press.

In May 2007 Melinda and Meng came across a pair of nesting Grey-rumped Treeswift (Hemiprocne longipennis) in a patch of secondary growth in the north of the island. They built their nest attached to a slender branch of an acacia tree (Acacia auriculariformis) some 20 metres high. The sexes are easily distinguished, with the male having rufous ear-coverts (left top) and the female blackish ear-coverts (left bottom).

The nest is a half-saucer made from hardened saliva incorporated with feathers, mosses and flakes of tree bark. Ornithologists believe that the feathers come mostly from the bodies of the birds themselves.

Chantler (2000) reports that the single egg laid is stuck to the nest surface with saliva. And because the nest is so frail and delicate and only attached at its side to the branch, the bird does not sit directly on the nest during incubation. Based on the images obtained, the weight of the bird was obviously not wholly on the nest. It was sitting on the branch and had its tarsus over the nest with the talons clutching the nest edge. This position allowed the brood patch to make contact with the egg. Gibson-Hill (1950) has similarly reported that the parent birds brooded by perching on the branch above the nest and fluffing their breast feathers out to cover it.

Both birds helped incubate the egg. Melinda and Meng witnessed the changing of shift three times, at 1.20 pm, 1.30 pm and 1.40 pm on three different days. Each time the female flew in and carefully perched besides the incubating male (below left). The male then flew off and the female carefully slided over the nest (below right). On one day there was no bird incubating the egg at 1.00 pm. However, 20 minutes later the female flew in and settled on the nest. Unfortunately, before they could observe when the male flew in to relieve the female for incubating duty as well as make other observations, the tree was heavily pruned and the nest destroyed.

At shift changing time, the incubating bird flew off at an angle, dropping backwards. This no doubt helped minimised the chances of the feet lifting the egg from its shallow bed as the bird flew off. Again, this is consistent with the observation made by Gibson-Hill (1950).

The images below by Daniel Koh of the bird at rest clearly show the characteristic long wing tips crossing over the shorter forked tail.

Some details of the nesting have been posted earlier.

Input by Melinda Chan, YC and Wang Luan Keng; images by Chan Yoke Meng except bottom panel by Daniel Koh.

References:
Chantler, P. (2000). Swifts. A guide to the swifts and treeswifts of the world. New Haven & London: Yale University Press. (2nd ed.)

Gibson-Hill, C. A. (1950). A note on the Crested Tree-swift. Malayan Nature Journal, 5: 5-8.