House Crows and juveniles of Asian Koel

The Asian Koel (Eudynamys scolopacea) is a cuckoo and brood parasite. In Singapore, it makes use of the House Crow as its host; laying eggs in its nest and leaving its young to be raised by the crows as foster parents.

“In mid April 2011, I came across a murder of House Crows (Corvus splendens). They were cawing loudly. Some were in the trees (left) and some circling around. Hearing some noise, I took peeps into the dense foliage of a tall tree. A juvenile Asian Koel was discovered hidden high in the canopy. The cawing crows must be protecting this juvenile, which may have fledged not too long ago. Although aware of the danger from the intimidating crows, which have strong parental instinct to protect their young, I decided to watch. It must be cautioned here that some nesting birds have high protective instinct and are known to dive-bomb much larger creatures; including humans. I have witnessed nesting crows and even small swallows dive-bombing at people who, inadvertently, went too near their nests. I will have to stay alert and keep an eye on the crows. One of the crows must be one of the foster parents as it came down low to guard against my intrusion.

“In the past I have seen crows cooperating with each other to protect their young. This time, however, not only did they chase after an adult koel that was around, two crows were spotted chasing after one of their own. I saw food being carried to the juvenile koel, but cannot see the actual feeding due to obstructive view. Later, I was surprised to discover yet another juvenile koel that was hidden in an adjacent tree next to the first. Hence, there could be a possibility of more than one nesting. This could explain why the crows were even chasing after their own kind.

“Now, how can I be certain that there were two juveniles when they were seen separately and not together? To be honest, I was not that certain in the field. I have to check through and examine the images in detail to be certain. I could conclude that there were two distinct juveniles as there were obvious differences in the eyes and plumage. Juvenile ‘A’ had brown eyes (above left) while Juvenile ‘B’ had grey eyes (above right). Another distinct difference was in the white markings that were along the gape. It was more prominent and longer in Juvenile ‘A’ than in Juvenile ‘B’.

“Two weeks later, a revisit to the site yielded only Juvenile ‘A’, which was still around. Its foster parent crows were still guarding the juvenile; but they were in a different tree. As for Juvenile ‘B’ , it was either very well hidden or was no longer around. A composite image of ‘Juvenile ‘A’ is enclosed for comparison of its plumage difference after 2 weeks (above).”

Kwong Wai Chong
Singapore
12th June 2011

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3 Responses

  1. The House Crow is noted as a brood host for Koels. In Ipoh we have hardly any House Crows but the Koel population has mushroomed over the past 20 years. Possibly using Mynas as hosts as well.
    Amar

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  2. Sun Chong Hong

    Few House Crows in Ipoh – does it imply Ipoh is a clean city? I know it is a big problem in Klang.

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  3. Sun Chong Hong

    There is a possibility that the two juveniles are in the same brood – from the same foster parents. The article “Less Crows…More Koels…” published on 13 Jan 2013 confirmes my believe that the Koel population is increasing. It becomes easier for Koels, which may outnumber the crows during the raid of the latter’s nests, to lay two or more eggs.

    http://postimage.org/image/fpgnyp2cj/ shows a pair of adult Asian Koels which I regularly saw together in the early parts of 2009.

    http://postimage.org/image/uwwnj1u77/ – this is a more recent picture taken on 20 Apr 2012 of two junveniles in a Trumpet tree (Tabebuia rosea).

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