Around the time when Angie was monitoring a House Crows’ nest (Corvus splendens) from her apartment window, Hung Bun Tang was doing the same from his apartment balcony. With the aid of a pair of binoculars, he could clearly see a crow sitting in the nest most of the time. However, to check the contents of the nest he had to walk to the next block and station himself at the fourth level. There, he patiently waited for a strong gust of wind to move the leaves blocking his view of the nest. That was how he managed to capture the excellent images included here.

He did just that on 5th December 2005 and again the next day. After a short holiday, he again checked on the nest and my, was he surprised!

In Tang’s very own words: “There is a crow’s nest near my place. I first noticed it on 5th Dec. and saw a naked chick and an egg in it. The next day when I checked it, the chick was gone and I saw only the egg. Then I went off to Taiwan for 2 weeks’ holiday and returned to Singapore on 21st Dec. When I checked the nest this morning, there were 3 eggs!!! I am really puzzled.”

The most probable scenario is that an Asian Koel (Eudynamys scolopacea) raided the nest and removed the crow’s nestling. Subsequently the koel probably laid one or even two of the three eggs he saw on 21st December. Exactly what happened, we will never know, but if he manage to keep close watch of the hatching of the three eggs, we may be able to know whether the above conjecture is true.

Contribution and images by Hung Bun Tang

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I was watching an Asian Glossy Starling (Aplonis panayensis) perched on the ripened fruiting bunch of my Alexandra palm (Archontophoenix alexandrae) one morning when I noticed it regurgitating a seed. This it did a few times before picking out one to swallow (left). The nearly rounded 10×12 mm fruit has a covering of pulp that is less than1 mm thick. This coral-red covering encloses a single seed.

Intrigued by this behaviour, I asked around but even seasoned birdwatchers could not give me an explanation. Then I stumbled upon a paper by Richard Corlett and his student on the Asian Koel (Eudynamys scolopacea).

Because frugivores generally have a reduced protein requirement, they can easily subsist on a fruit diet. Such birds also exhibit a high ingestion rate and a short gut retention time, as well as reduced loss of nitrogen through the faeces and urine. Some of these birds supplement their protein requirement with insects or the seeds in the fruits they ingest.

The study shows that Asian Koels swallow large fruits like those of Chinese fan palm (Livistona chinensis), Syzygium chumini and Arenga engleri whole. But they rapidly regurgitate the cleaned seeds, dropping them under the tree, rather than defecating them. This appears to be a common adaptation of specialist frugivores, presumably serving to reduce the weight and volume of material that must pass through the gut. On the other hand other birds peck the fruits and leave the seeds. When eating fruits like figs with small seeds, koels swallow them whole and defecate the seeds below the tree.

The intake of indigestible seeds results in extra load in the gut. The energy expenditure necessary for flight is thus increased. Additional energy may also be required to manipulate the seeds in the gut, separating them from the pulp and transporting them through the gut. Again, the presence of the indigestible seeds in the gut limits further food ingestion. This in turn reduces the rate at which food can be processed and nutrients assimilated.