Dr Ivan Polunin lives in Hillview, off Upper Bukit Timah Road. Fronting his house is an old and very tall durian tree (Durio zibethinus) (left). For the years he has been living in his current house, he claims that he has yet to taste the fruits.

Every fruiting season the tree gives forth many fruits. These invariable fall when ripe. All the fruits on the ground would have been damaged by the Common Red-bellied squirrel (Callosciurus.notatus), also known as Plantain Squirrel.

During the last flowering season there were numerous flowering buds that developed into flowers. The squirrels came regularly to feast on the fleshy petals. He filmed the flowers one night with the aid of infra-red lamps. The video was on for an hour but there was no sign of any bats visiting the flowers.

As there were no bats pollinating the flowers, Ivan concluded that the squirrels must have done the job. In the process of eating the petals, they must have invariably transferred pollen to the stigmas.

For the record, the literature reports pollination by bats and night-flying moths. Pollinating by squirrels may be something new.

The flowers eventually developed into fruits and when the ripening fruits were at the optimal ripeness (from the squirrels’ standpoint), the squirrels came and gnawed an opening on the spiky fruit wall of each and every fruit - to get at the succulent flesh (below left).

The squirrels had first priority of the flesh. Then the White-crested Laughingthrushes (Garrulax leucolophus) took over from the squirrels (above right).

So far, we have documented Orange Bellied Flowerpeckers (Dicaeum trigonostigma) and Plain-throated Sunbirds (Anthreptes malacensis) eating the durian flesh: see HERE. There is also a claim that the Javan Myna (Acridotheres javanicus) was seen at the fruit. The Perak Bird Group of the Malaysian Nature Society has documented on video a Black-naped Oriole (Oriolus chinensis) feasting on the fruit.

Images of durian by YC and of squirrel-durian and laughingthrush by Johnny Wee.

The Malayan Water Monitor (Varanus salvator) has made Sungei Buloh Wetland Reserve its home. Once relatively scarce, it is now common to see them along the main paths, in ponds and even around the entrance, so much so that the lizard is a minor attraction (above).

The lizard is an excellent swimmer, in fresh as well as saline waters. It can remain submerged in the water for up to half an hour. It can move with good speed relative to its size on land. It also climbs trees when the situation demands.

This is one of the larger lizard in the world and can grow to over 2 metres long. Shy by nature, it does not appear to be shy in the reserve. Most of the times it will back off when approached too near. However, visitors should leave the monitor lizard alone and not confront it, as larger ones can be dangerous and their bites can cause serious injuries.

It is a carnivore as well as a scavenger. Most of all, it is an opportunistic predator. It will eat almost everything that it can swallow. Its diet includes small mammals, snakes, lizards, young crocodiles, tortoises, birds and their eggs, fish, crabs and molluscs. However, it prefers carrion.

The lizard hunts by pursuing, rather than stalking or ambushing prey. And it regularly raids bird’s nests.

It has been brought to our attention that its presence in such numbers at the reserve can be detrimental to nesting waterbirds.

The Little Grebe (Tachybaptus ruficollis) (left top) has never been sighted in the reserve. Can its absence be due to the presence of the lizards? The Lesser Whistling-duck (Dendrocygna javanica) used to breed in the area but no more. However, its absence, according to Wang Luan Keng, can be due to the presence of the snakehead (Channa sp.). Some years ago she saw a duckling being swallowed by the fish in a freshwater pond. The Common Moorhen (Gallinula chloropus) (left bottom) was sighted recently by KC Tsang but whether it is nesting in the reserve is another matter.

A pertinent question is, should the population be culled to a manageable level?

Other postings on Sungei Buloh Wetland Reserve: 1, 2, 3, 4, and 5.

Input by KC Tsang and YC, images by KC (montage: top left, bottom right; Common Moorhen), Chan Yoke Meng (Little Grebe) and YC (the rest).

References:
1. http://www.cyclura.com/modules.php?op=modload&name=News&file=article&sid=104
2.http://animaldiversity.ummz.umich.edu/site/accounts/information/
Varanus_salvator.html

On 13th November 2007, the Little Heron (Butorides striatus) has been under care for 11 days. All this time it was fed pieces of fish fillet, later pieces of whole fish. The bird was offered the pieces at the end of a pair of tweezers. It lunged at the pieces and immediately swallowed them, taking two to three pieces one after the other, although sometimes it had difficulties getting them down its throat.

Then it was transferred to a large cage (left). The sides of the cage needed to be lined with newspapers as it kept on trying to squeeze through the wires. Here, its behaviour changed. Every time it was fed, it took the first piece offered, refusing subsequent pieces, until an interval of time.

On the 13th evening I tried a strategy suggested by Victor Lee: “…As to learning to forage, what I used to do at Jurong BirdPark was to put birds like these inside a paddock with a small pool, etc. Put in live fish, tadpole, frogs, etc. and get them to work it out themselves. When they are hungry enough, they will forage and learn to pick up the live food. Hope this helps.”

So I purchased a bag of mixed guppies and mollies sold by aquarium shops for feeding predatory fishes kept by hobbyists. Two dishes, each with nine fish were placed inside the cage. One was a shallow dish (right), the other deeper.

The bird, not fed for the last six hours, simply stared at the fish in one dish, not moving a step. When I dropped a piece of the usual fish inside the dish together with the swimming fish, it took the piece and swallowed it after about ten minutes.

One of the live fish jumped out of the dish and died. This dead fish was placed on a spoon and left inside the cage. It was subsequently eaten.

Three hours later when I looked inside the cage, the shallow dish was devoid of fish. The bird had eaten all the eight remaining fish, leaving the fish inside the deeper dish uneaten. Overnight, the nine live fish in the deeper dish were also eaten save for a dead one floating in the water. This was removed from the dish and offered to the bird who immediately took it.

The images above show the sequence of the bird taking the fish from the deeper dish the following day.

When the guppies and mollies were all eaten, I got small goldfishes that were slightly larger. When offered in a dish of water, the bird went straight for one but the fish slipped out of its grasp before its head could be positioned for swallowing (below). It had to try again a few times before it succeeded in swallowing it. Subsequent attempts also had to be repeated.

After eating more than 30 goldfishes, the bird became well versed in handling the fish. Just before posting, I fed the remaining five and it took every one of them head first and swallowed them on the first attempt.

So the experiment is a success, thanks to Victor Lee. The bird should have a reasonable chance of survival when released into the wild.

“Give the bird a fish and you feed it for a day. Teach the bird to fish and you feed it for a lifetime.”

Images by YC.

An image by Melinda Chan shows a male Brown-throated Sunbird (Anthreptes malacensis) robbing nectar from a hibiscus flower by probing his bill through the base of the flower (left).

Now why did the bird do that?

The natural pollinator of hibiscus has been reported to be the hummingbird. The sunbird is not adapted for hibiscus pollination, so to harvest the nectar in the flower, it has resorted to the unconventional method of probing the base of the flower. This is referred to as robbing, as by doing so the bird is not doing the flower a favour, i.e. assisting in its pollination.

Hibiscus or China rose (Hibiscus rosa-sinensis) is native to continental Asia, probably China. The species has been in cultivation in various forms for centuries and the species itself has never been found in the wild. In Singapore, the plant never produces any fruit or seeds.

The Little Heron (Butorides striatus) chick rescued from the Bukit Timah campus is now more than a week under my care: see 1 and 2.

The wings are now well developed but it is still unable to fly. But it can easily run off if left unattended. Soon, it would be time to set it free. The one big question is how to do it.

Many birders are of the opinion that newly fledged birdlings need to be taught how to forage for food and herons are no exception. It had been hand-fed until now and whether it can fend for itself, hunting for fish and insects, is foremost in my mind.

It can be released at the Eco-Lake in the Singapore Botanical Gardens, around where it was found. Hopefully it may be able to observe other Little Herons hunting. Or it can be handed over to the Jurong BirdPark, where there may be more of its kind around.

The image below was taken on 6th November, four days after taking it home. Will we be releasing the chick to meet its death in the wild?

A number of people very kindly sent in their views/experience/advice in response to our earlier post and we reproduce them below:

Lin Yangchen has this to say: “Afraid I have no sure-fire recommendations but I think the problem is not so much when to release it as whether it will survive after release. The problem is that it has no parent to demonstrate what kind of food it should look for and how it should catch the food. Just based on these deductions, I think that the best thing to do might be to find a place where there are adults of this particular species and release it, hoping that it would be ‘adopted’ by one of the adult birds. Although we know that many species usually ignore young that are not their own, I think there are occasional incidents of adoption in animals whether birds or not. Otherwise, the next best options might be either to let the bird loose in an appropriate habitat and let nature take care of itself through natural selection, or keep the bird as long as possible and take the opportunity to study aspects of its biology and behaviour.”

Charlene Yeong, Conservation and Research Officer, Singapore Zoological Gardens wrote: “I saw your message on the BESG blog a few days ago; apologies for the late reply. How is the little heron doing? I’m not sure if you’ve already received much advice from others who have experience with raising birds, but here is a message from one of our curators.

“I don’t believe the vet department has raised a heron before, although we recently raised a stork. It was hand-reared on fish (as mentioned in Doug’s email below) in the ward, and eventually mixed with our other adult storks. It was full-grown by that time. I think it may have been better if he had been raised in an area with visual/auditory/olfactory access to other storks. Having said that, though, he seems to be doing well with the other storks. If you’d like to get more details, you can get in touch with our head vet, Dr Serena Oh, whom I am copying this email to.

“I hope all is well, and the heron is well and not causing too much trouble!”

Charlene appended the notes from Douglas M Richardson, the Zoo’s Curator (Zoology): “If the chick was very young when found and/or reared in the absence of other birds, which it seems it was, it is likely that it may not recognize other herons as members of its own species. If the bird is at least old enough to feed itself (it should at least have some experience of catching fish in a small pond or similar area) it should be released in an area that is frequented by other herons. The bird may readapt quite quickly, as the hand-reared stork from the lab that was mixed with the others in the new holding cage did. Of course there is a good chance that it may be predated upon by a python, monitor or crocodile, depending on the release site, but it is worth the gamble and carnivorous animals need to eat as well. Prior to being released, which is when it no longer has downy feathers, it should be rung above the “knee” and not around the “ankle” so that it may be identified later.”

We appreciate the above feedback that will come in useful when the heron chick is ready to be released into the wild.

Image by YC.