Not crow also complain

Last Saturday, a Daniel Ng wrote to the Straits Times Forum complaining that the “distinct and piercing”, “loud and aggressive” calls of the Asian koel wake him and his family up at 5 am. He used the word “invaded” to describe the unwelcoming barge of these “large black birds” into of his lush Queenstown HDB estate.

To his chagrin, AVA told him that the bird is protected, and “offered to trim the trees to reduce their roosting areas”.

The man demands to know why the bird is protected and what AVA is going to do about it.

Yesterday, there were a flurry of letters published in response.

A Sia Beng Choo reports similar torture at the hands of the koels, claiming that they “screech loudly and incessantly… even as early as 4 am”.

Yet others spoke up on their behalf: be grateful that there is still some nature in this city, and if you want lush greenery, you have to put up with some quirks. As we say sarcastically in our lab, people want beautiful birds without anuses, and beautiful butterflies that magically appear without the caterpillar stage. Not happening.

Over the past decade, the koel population has indeed increased by almost an order of magnitude on average throughout Singapore. In fact, the first letter came coincidentally on a morning when I was also woken by a rather insistent koel at an unholy hour of 6 am. Three other friends (including one of the same name of the first letter writer) similarly mentioned first calls at times ranging from 4.30 am to 6.30 am.

But populations of quite a few other bird species have increased. We recently published a paper on this. A modified version will be going into my thesis.

What is interesting about the koels is that their preferred host for their eggs are the house crows. Yes, koels make a cuckoo out of another unwelcome big, black bird. You would have thought that it would be a redeeming factor.

The house crow is alien to Singapore, while koels are native (although they may have been more of open country species, not quite so common when Singapore was covered by dense forest). Koels may have originally parasitized nests of the large-billed crow before the house crows arrived, but the former are rarely found in urban areas, which Singapore consists most of, and the latter are fully urban species. Using house crow nests enable the koels to expand their usable space in our city.

When the population explosion of house crows became an acknowledged problem some decades back, the government had to do something about it. Research was conducted by Navjot‘s team and a level of culling was determined. The culling intensified in the early 2000s, and today house crow populations are not quite so crazy.

Curiously, you would expect the parasite to decline when host numbers go down, but the numbers of the koel have gone up instead. Why is that so?

In our paper, we suggested that host switching is an immediately obvious possibility. But the real reason may be a bit more esoteric. We found studies in India and Bangladesh that showed that success rates of nest parasitism by the koel increase when the density of house crow nests are lower.

When house crow numbers are high, they can nest gregariously, and this is suggested as a neighbourhood watch program to chase off unwelcome intruders.

Culling house crows to low numbers but not completely eradicating them means that they are still around, and they build rather solitary nests. Without neighbourly lookouts, they become more vulnerable to the tactics of the koel couple. The koel prospers instead of declining.

Or so we suspect.

The koel is also a frugivore, so it has no worries about going hungry given the kind of plants one can usually find in the urban area.

Regarding the “protected species” thingamajig, it’s an artifact of outdated, uninformed biodiversity laws in Singapore. Only a few bird species can be killed; all others are protected. Not so much a bad thing, actually, just that some species that don’t deserve to be are put on the hit list.

(This is actually the first time I’m blogging about ideas from a paper I’ve published, hmmm…)

Update on 11 November 2012:

An article on Thursday on the koel fuss by ST journalist David Ee.

A student from Chai Chee was quoted as being woken up at 5 am by the “sharp and irritating” calls, consequently getting headaches and was unable to study well…

I remember hearing the koel’s sounds when I lived in Chai Chee, although I never knew they were called koels. In the last few years when I became a bit more ornithologically literate, I found out that on those morning trudging out to school at 6.20 am, I not only heard koels but also the golden-bellied gerygone’s melody.

AVA continues to think that reducing (but not eradicating) house crow numbers is the way to go. I still think that reducing house crow nest densities but not below a threshold that is enough to affect the demographics of koels would perversely benefit their numbers.

By the way, it has already been documented that Asian koels are able to parasitize nests of the black-naped oriole, another bird whose population trends show that it has benefited from the urban landscape in Singapore.

Advertisements

3 Comments

  1. 13 January 2013 at 19:47

    […] Thanks to Chong Kwek Yan LINK who kindly sent me a PDF of the paper by Begun et al. […]

  2. Johnny said,

    28 February 2013 at 09:31

    Sir, I am having problems with the Asian Koels and have had futile communication with AVA regarding this. It is good to see an article like yours regarding this matter. Do you any resources I use to help me argue my case with AVA? Thanks.

  3. kwekings said,

    28 February 2013 at 13:39

    Hi Johnny, maybe you’d like to elaborate a little more about your issue? To be frank upfront, I’m not really an expert on birds, but would be happy to discuss.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: