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Tuesday, January 03, 2006

Tang’s nesting crows 1: Whose eggs are these?

Tang’s nesting crows 1: Whose eggs are these?

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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2 Comments:

At 10:36 am, Blogger KF said...

Looks to me like the mimicking is clever done by the koels. There are 2 egg-shapes in the nest; one egg is different from the other 2 rounder & shorter eggs. Together with the brown mottling & similar colouring on the egg shells, it becomes pretty difficult for the crow to tell the difference. Questions are: (1) are there really eggs of both species in the nest? (2) which egg/eggs belong to the crow? (3) is it always the cruel practice of all koels to eject the eggs & chicks of the crow or that some koels do not do so? Intriguing!

 
At 6:08 pm, Blogger Jun Ying said...

This is a follow through of KF's (3). Hmmm... Is it possible that Koels go for nests of other birds? There are similarities in egg shell colouration and also plumage of the male koel and the crows, but surely the koel has also tried other nests? And if so, have they failed due to being spotted during the "hijacking" process or recognition by bird with largely different eggs. Koels going for Crow nests, learned behaviour?

 

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