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.

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.

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.

“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.

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