Saturday, November 01, 2008

29th October 2008: Swiftlets

Lord Cranbrook came to give a talk on swiftlets and swiftlet-farming for MNS today. In preparation for the talk, Choo Eng and I went to look at a couple of swiftlet farms near Sungai Petani.

Getting into a swiftlet farm is a bit like getting into a diamond mine, and I was advised not to take pictures of anything except the birds themselves.

Faces only a mother could love! The nest is made from saliva secreted from under the swiftlet's tongue. The 'white-nest' group of swiftlets (comprising several species) makes the nest purely of saliva, whereas Black-nest Swiftlets (one species) mix in at least 50% of their own feathers to make the nest. The few feathers in this nest are there by accident, from the parent birds as they were building the nest. Another difference between Black-nest and 'white-nest' swiftlets is that the former lay only one egg, while the latter usually lay two.

This is the 'porcupine' nestling stage, when most of the feathers are still in pin. You can see the plain, unfeathered tarsus, which is another distinguishing feature of the 'white-nest' group. Unlike passerines in Malaysia, which have a very sort nestling stage (around 2 weeks), swiftlets spend an extremely long time maturing in the nest - 'white-nest' swiftlets on average spend 45 days at the nestling stage. In their natural habitat, swiftlet nests are much less vulnerable to predation than passerines, which means that they can afford to take longer maturing.

By this time it looks as though the nest isn't big enough for both birds, or maybe this one just prefers hangin' out! Swiftlets normally breed three times in a calendar year, making them extraordinarily productive. This is good news for the swiftlet farmer. After birds have finished nesting, a proportion of the nests in the 'farm' are harvested. A kilo (roughly 100 nests) can fetch around US$1,200 (or GBP700)! Birds are highly faithful to nest sites, so will come back to rebuild a new nest at the site of the old one.

Two almost full-grown nestlings. So what are these birds, other than being one of the 'white-nest' species? Lord Cranbrook told us that the situation is complex. For one thing, the birds that have begun seeking out nest sites in buildings appear to be different (darker-rumped) than the birds that breed in caves, even within the same geographical area. For another, there are incidences of swiftlet-farmers importing swiftlet eggs from geographically different areas to be fostered and reared by swiftlets in their own farms. No-one is really sure how widespread a practice this is, and the industry is a notoriously secretive one.

Here's an adult bird. The rump colour is difficult to judge in these lighting conditions. It seems to be pale, but not very pale! Could this be the darker-rumped 'amechana' subspecies of German's Swiftlet, which is supposed to occur naturally in this area?

These were taken over the swiftlet farm, so there's a reasonable chance that these are the adults from the colony.

This one is easier! Here's a Pantala flavescens. These dragonflies are one of the commonest around, often occurring in quite dense swarms over open areas. I've never seen one perched!

The talk on swiftlets took place on Penang Hill. Afterwards we were treated to amazing views of the city at night.

And a couple of resident Wagler's Pit Vipers - this juvenile ...

... and here's an adult. Looks mean!

1 comment:

jytou said...

Could your swiftlet in flight be a Himalayan due to a rather deep and obvious fork on the tail? I guess it would not be too surprising if these migrants decide to feed alongside with other swiftlets.