The chick of the Oriental White-eye (Zosterops palpebrosus) is hatched blind and naked (top left). The natal downs or down feathers that usually cover chicks at hatching are generally absent here, as in most passerines. Traces of these downs can still be seen around the head as isolated tufts of light green (top right, arrow). The absence of natal downs allows the parents to warm the chick more efficiently, than through an intervening layer of feathers. Not wasting energy producing these natal downs would also allows the chick to develop more quickly.

The chick is not naked for long. By the next day traces of emerging pin feathers become apparent along certain defined tracts on the body (right). These black, pencil-like structures elongate (below left) and the developing feathers enclosed within the sheath breaks out eventually, to emerge as juvenal feathers (below right). These juvenal feathers are light green and branched.

According to our field ornithologist Wang Luan Keng, the green juvenal feathers (below) are of poor quality: “The bird will change into its first year plumage after it is out of the nest. They look branched because it is poor quality (meaning the barbs are loose, the vane incomplete). This is a strategy for growing quickly but they are poor quality, meaning they do not afford much insulation and must be changed into better quality plumage.

“We know very little about feathers, really. Very few documentations are available. Any bird is capable of growing low quality feathers. Most try not to. In nestlings, it is a strategy in response to environmental factors, a life history trade-off - to grow quickly and get out of the nest and be independent. In adult birds, we sometimes see fault lines, especially in the flight feathers (both wing and tail). It is due to feather growing in poor environmental conditions (which means low nutrition, which means poor feather growth).

“Birds usually grow their feathers very slowly, about 2-6 mm a day. This is because feather growth is very energy demanding. In unfavourable environmental conditions (even for a day), birds can still achieve the same amount of feather growth but the new part of feather grown is much thinner (fewer/looser barbs). When the feather is completed, the thinner part of the feather shows up clearly as a “fault line”.

For nestlings, we have very little baseline studies on how fast the feather grows. If we have the photos of the white eye nestlings in last June, Jan and this March (1, 2), and all taken on Day 7 (this is the day the Jan clutch left the nest - the earliest so far), we can enlarge the feather and see if the Jan clutch indeed grow much faster by growing poor quality feather).

Fascinating isn’t it?”

Yes, it is fascinating and we know so little about it. But with the cooperation of photographers documenting chick development, as in the case of the white-eyes, we are slowly accumulating information on feather development in chicks. The image above shows a chick with its juvenal plumage all developed and allready to fledge within a few days’ time.

Input by Wang Luan Keng and YC; images by Chan Yoke Meng except second from bottom by KC Tsang.

It was the 11th April 2007. It was evening, round about 6.30 pm. It was beginning to get dark, but not yet. Morten Strange was walking past this patch of growth in the Singapore Botanic Gardens where there are many mature palms, just after the Botanic Gardens Shop.

As he walked, he noticed seven Javan Mynas (Acridotheres javanicus) foraging along the undergrowth. Suddenly one myna picked up an ant in its bill and swiped it over its plumage. It then picked up another and another and another. Each time it picked an ant, it swiped it over the feathers, but whether it ate the ant or released it afterwards, Morten was not able to say. It was rather dark, the ant was small and the action was rapid.

The action of the first myna seemed to trigger the six others to do the same. Suddenly there was a frantic mass anting by all the birds, each picking up an ant, swiping it over its feathers and repeating the action a few times.

According to Morten, even if he had a camera with him, he would not be able to document this mass anting. The action was so rapid and the ants so small. How would he be able to capture this on film or the memory card?

For those not familiar with anting, this is a method of cleaning the feathers of ectoparasites with the help of ants. The formic acid released by the ants help to do the job.

Anting was explained to the birding community in October 2005 when the Bird Ecology Study Group posted an account observed by Kelvin Lim some 17 years ago. Since then, there have been a number of reports by birders (1, 2 and 3).

There are always plenty of Javan Mynas at the Singapore Botanic Gardens (below). Apparently it is easy to witness these birds indulging in anting. However, one must be alert to it as the action is sudden and will take one by surprise.

Input by Morten Strange, images by YC.

Since 1998 a pair of resident Oriental Honey Buzzard (Pernis ptilorhyncus torquatus) in the Royal Perak Golf Club, Ipoh, Malaysia, has been coming back to nest yearly (1, 2). Most of the time they produced one chick only but twice they produced and unsuccessfully attempted to raise two chicks.

The first attempt was the October 2001-March 2002 nesting. One of the two chicks died while still covered with white down. The other was found dead at the foot of the nest tree just days before fledging. The second attempt at raising two chicks was the November 2004-March 2005 nesting. Here, one of the fledglings was run over by a vehicle not long after fledging while the second fledgling disappeared and was never seen again during subsequent visits.

The resident pair returned to the golf course on 1st November 2005 and built their nest from 3rd November-13th December 2005. Nest foundations were built on three different tembusu trees (Fagraea fragrans) before the pair finally selected their nest location.

Copulation was observed from 26th November 2005 onwards. On the 5th and 13th December 2005, the male thwarted attempts by a pair of Crested Goshawk (Accipiter trivirgatus) to build a nest in a nearby tembusu tree.

On 17th December 2005, laying of egg(s) or incubation commenced. The male brought food to the female who remained in the nest all the time. By 18th December 2005, laying of eggs was assumed completed as the male was seen sitting in the nest. The very next day, eight to nine Large-billed Crows (Corvus macrorhynchus) launched an unsuccessful attack on the nest in an attempt to force the female to vacate and expose the egg(s).

Initially, on 30th January 2006, one chick about 7-9 days old in fluffy white down was sighted in the nest but on 6th February it was confirmed that there were actually two chicks.

The chicks were guarded all the time until they were about 12-14 days old when the female started to leave them on their own in the nest for short periods for the first time. At 32-34 days old, the chicks were generally left by themselves in the nest while the female stood watch from nearby trees. As similarly noted on previous observations, the pair copulated again while still caring for the young in the nest.

The chicks were fed with honeycomb and meat, provided for initially by the male. The female only provided food later. At 41-43 days old, the chicks were able to tear the honeycomb and meat into smaller pieced in order to swallow them.

On 10th March, at 46-48 days old, one of the chicks fledged but continued to roost in the nest for the next five days. The other chick fledged three days later, to also return to roost during the next four days.

After the chicks had fledged, the adults continued to drop off food in the nest until 13th April. For three weeks after fledging, the juveniles remained within 40 m of the nest tree and thereafter started to explore other parts of the golf course.

On the morning of 20th March, the adult pair each brought back a big piece of honeycomb and dropped them in the nest. Both the juveniles flew back to the nest and were observed tearing up the honeycomb with their bill and claws and then eating whole pieces of honeycomb. Jeyarajasingam & Pearson (1999) states that Oriental Honey Buzzards principally eat bee and wasp larvae but our observations that day revealed that they eat the honeycomb too.

Other food items brought back or fed to the fledglings included a young bird. On 30th March, Connie Khoo observed the adult female raiding the nest of an unidentified bird. She raided the nest three times, each time carrying out an egg with its bill to feed to one of the juveniles which swallowed the egg whole. It was noted that the juveniles partially depended on the adults for food 34 days after fledging.

On 13th April, Connie saw one of the juveniles dived from its perch on a high tree into a lower tree in which small birds were feeding/perching. It did not succeed in catching any and flew back to the same perch. It tried again before finally succeeding on its fourth attempt in catching and eating either a Eurasian Tree-Sparrow (Passer montanus) or sunbird.

Another observation made was that the adult Oriental Honey Buzzard have three types of calls. Previously, two calls were identified: a string of notes and a short call heard given out by the male during the 9th nesting when bringing food to the fledged juvenile. This season, a third type of call was heard given by the female which sounded like the “pee..ooh” call of the juvenile but shorter and with a deeper tone.

On 28th March, Connie again saw one of the juveniles peeling bark from the branches of a tree. Later it was seen swinging upside down on a branch before perching upright and then swinging upside down again. This went on for 20 minutes and was probably a form of “play-exercise” to strengthen its leg muscles and grip. Continued sighting of both the healthy-looking juveniles around the golf course on 19th April 2006 was a reassuring sight.

Breeding chronology for this season:
Nest building to 1st juvenile fledging: 127-128 days
Incubation to 1st juvenile fledging: 83-84 days
Incubation to hatching: 35-36 days (previously 42-47 days)
Hatching to fledging: 46-48 days

Input by Chiu Sein Chiong who wishes to thank Connie Khoo Siew Yoong for her patience in spending many hours observing and taking photographic records of the juveniles during the post-fledging period. Her contribution has resulted in new data being obtained. I also wish to thank Ooi Beng Yean, Cheang Kum Seng, Dr. Chan Kai Soon and Susan Cheong Suit Kuen for their participation in the observations and for taking photographic and video records.

The above was first published in 2006 - Chiu, S.C. 2006. Oriental Honey Buzzards Succeed on Third Attempt at Raising Two Chicks. Suara Enggang (2): 15-16, 18.

Reference:
Jeyarajasingam, A. & Pearson, A. (1999). A Field Guide to the Birds of West Malaysia and Singapore, Oxford University Press, UK.

Angie Ng read an earlier account of the courtship behaviour of the Olive-backed Sunbird (Cinnyris jugularis) describing the mating dance of the male bird and suggested that I get KC Tsang to give his version of a sexier mating dance of the bird. KC has kindly agreed and sent in this account:

“I was strolling along at Bishan Park on the morning of 29th March 2006 looking for birds to photograph. Suddenly five female Olive-backed Sunbirds dropped in onto a plant right in front of me. All of them were chattering with great excitement. Then out of the blues a single male also descended on to the same plant.

“Then looking up from his perch at the females, the male began to vibrate, and the wings opened out, also vibrating in great frequency. What was most amazing, and for me a first-time observation, was that the male had these orange-yellow fluffs of fine feather extending out at the very same moment, from his shoulders (left). I am not sure if these feathers can be called lesser coverts.

“Besides vibrating, he also moved from side to side and tried to get nearer to the females. Apparently the females were not impressed or were they playing very hard to get? They flew off to another tree with the male following close behind.”

Yes, this is another version of the mating dance and by far a sexier dance. According to our field ornithologist Wang Luan Keng, these are pectoral tufts, developed by the male during the breeding season. “The male opens his wings, flutter them and display the orange tufts to attract the females. I have never observed it myself so am not sure of the detail behavioural traits. I don’t know if the female chooses her mate based on how orange the tufts are, or how big or a mix of various characters. Maybe you can get photographers to document this behaviour.”

The only other sunbird reported to have pectoral tufts is the Malachite Sunbird (Nectarinia famosa) of Africa.

Input and images by KC Tsang

This is the breeding season. The Yellow-vented Bulbuls (Pycnonotus goiavier) are not building their nests in my garden but in my back neighbour’s (left). I have yet to locate it but it is definitely there. Everyday I see a pair in my curry-leaf tree (Murraya koenigii), perching separately or close together, sometimes preening, at other times calling loudly and ceaselessly.

Just the other morning (10th April 2007) the pair was crying repeatedly, belting off a series of chic-chic-chok-chok or chic-chic-chok, sometimes a combination of the two. They were perching together on a branch not moving except their tails flapping up and down. The crest feathers were somewhat raised in anger.

On looking closer I noticed the neighbour’s cat, a regular visitor, was lazing nearby (below). The birds were obviously scolding the cat. Their nest must be around somewhere as I have not heard such scolding before. After some five minutes or so, the cat moved off but the birds followed and kept on scolding it.

The cat moved on to the front part of the garden and there, a Javan Myna (Acridotheres javanicus) took over the scolding. This time the cries were harsh – kreak-kreak-kreak repeated many times until the cat moved away. If there was a squirrel, it would definitely have joined in the scolding.

Four days later, the pair of bulbuls was at it again in the same tree. This time the cries were different form before, cherok-cherok-cherok, it went on repeatedly.

At the sound of the alarm, I investigated. Perching on a branch and casually picking on the fruits of the curry-leaf tree was a large, black, male Asian Koel (Eudynamys scolopacea) (left). The koel moved slowly from branch to branch, seeking out the choicest fruits and completely ignoring the bulbuls. This time the bulbuls were not together but perched on different branches, some one metre from the koel. They were agitated and scolded the koel incessantly. Whenever the koel approached one of the bulbuls, it scuttered further away but kept on scolding. All the time the birds did not try to mob the koel, only scolding it.

A Eurasian Tree Sparrow (Passer montanus) was on the same tree but it did not appear to be agitated, chirping quietly on and off. Also there was a female Olive-backed Sunbird (Cinnyris jugularis), again part of the scene but not part of the action.

After about ten minutes, the koel flew off to a nearby waringin tree (Ficus benjamina). The bulbuls followed and maintained their scolding until the koel left the tree.

A week later I again heard the bulbuls’ scolding. This time the scolding came from the waringin tree. There, moving slowly around was another Asian Koel, this time a female. She remained in the tree for at least 20 minutes, all the time apparently deaf to the continuous noise generated by the bulbuls. In both instances the koels remained totally silent all along, not making a sound.

I am not sure how dangerous the koels can be to the nesting bulbuls, but the cat can be deadly. Even with all the alarm calls sounded by the bulbul and the myna, and even the squirrel, the cat gets to catch its prey once in a while, as seen in the dead Javan Myna I found under the curry-leaf tree (right).

Input and images by YC.