Pong pong tree

posted in: Plants | 5

The pong pong (Cerbera odollam) is a medium sized tree that was once commonly planted along roads in Singapore. Its popularity then was because there was a plentiful supply of large fruits that collected on the ground below. These were collected and easily germinated to be used as wayside trees. With the maturity of the garden city and availability of a more varied selection of tree species, pong pong became less of a favourite. Its general shape is not all that attractive. Besides, the large, round fruits that litter the ground below became quite of a nuisance. However, there are still many areas where such matured trees can still be seen.

The tree has been called Singapore apple because of the large, round fruits. The green outer covering of the fruit encloses a thin pulp and a thick fibrous stone containing a single seed. This seed is reportedly poisonous, containing the poisonous substances cerebin and odollin. It has been used locally to poison rats.

For a long time now no animals have been observed to eat the fruits, or at least the outer pulp. Being a coastal tree, the fruits are adapted for water dispersal, not animal dispersal.

However, birders have recently observed seeing Tanimbar Corella (Cacatua goffini) feasting on these fruits. Johnny Wee sent an image of this bird eating through the outer part of a green fruit, apparently chewing through the tough fibrous layer covering the seed. The bird is seen perched on a branch with its right leg tightly clutching it while its left leg clutches the green fruit.

At Eng Neo area, certain mornings the pong pong trees will be swarmed with these corellas as they noisily fly from branch to branch and tree to tree, pecking on the fruits. Typically wasteful eaters, these birds end up littering the ground below with the partially eaten fruits.

According to our bird specialist R. Subaraj: “Tanimbar Cockatoo (now known as Tanimbar Corella) was first seen around 1970s when it was misidentified as Little Corella (Cacatua pastinator) from Australia. A visiting Aussie birder in the mid-1980s said it weren’t theirs and that finally lead to the accurate confirmation of the species.”

This is an introduced bird, now getting more common. It has obviously found a feeding niche that no other birds have occupied before. Besides feeding on pong pong fruits, it also goes for green starfruits (Averrhoa carambola) and fruits of sea almond (Terminalia catappa), fruits not popular with other species of birds.

Images by YC Wee except second from top by Johnny Wee and bottom by Chan Yoke Meng.

5 Responses

  1. Hai~Ren

    Interesting. I’m wondering which of the following scenarios is likely:

    i) Tanimbar corellas are unique in being biologically adapted to breaking down the poison
    ii) No other bird in Singapore has ever explored this niche
    iii) Tanimbar corellas will eat the poisonous fruit, but have found a way to neutralise the poison.

    Do cockatoos and corellas feed on clay, just like macaws and other Neotropical parrots do? (if they do, it then raises the question of whether Psittacula parakeets do so as well)

  2. YC

    The corella has not been observed eating the seed proper, which is surrounded by a tough, fibrous layer. It would appear that no other bird has so far explored this niche – unless someone has evidence to the contrary. Interesting points re poison and feeding on clay. Need to check on these.

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