Thursday, January 27, 2011

Flying in the face

God in his wisdom made the fly
And then forgot to tell us why.

- Ogden Nash

Bengalia looking out for a victim
One of my favourite flies was a species of Bengalia found especially during the rainy season. You will find him or her beside ant columns, watching stealthily and then making a quick dash and stealing a pupa or snatching food out of the mandibles of a passing worker. It was actually years between my first observation and finding the identity of the fly. The identity incidentally was made possible thanks to the Internet, on an email group, at a time when the web was still in its infancy. I posted a description of the behaviour and was entirely surprised when it was identified to genus by Dr D P Wijesinghe. Apparently the food-stealing or kleptoparasitic behaviour has been documented from early times. I later learnt that hardly anything is known about the life-history of this fly, which got me wondering how could anyone find more information about something like this. Perhaps one should build a large glass case and use some kind of passive marker with some detection apparatus on it to see where it goes. For all the spy gizmos and nano-technology, there does not seem to be any way. The only way to find out seems to be look out for it and to be prepared for surprise.
Ochthera - probably males at a lek

Lots of times, it is so hard to see what's happening. During the last rains I noticed a swarm of tiny silvery flies that seemed to like sunbeams under shaded trees. They are so alert and swift that they cannot even be captured. And no they are not hoverflies (Syrphidae). I asked my entomologist friends but they too have not figured a way to capture a specimen ! 

Another time I found this large aggregation of flies on a leaf. They have their forelegs raised and it looks a bit like a hand holding a sword. The structure is actually even closer to a pen-knife with a groove and the flies are actually capable of grasping prey - midges and indeed, the scientific name means midge-hunter. Now what this large aggregation is about is hard to tell, I suspect they are mostly males.

There are a couple of spectacular Internet gatherings of entomologists and the two that stand out at the moment are and - one on flies and the other on hymenoptera. These sites gather information, photographs and reassemble them into very interesting nuggets.  They are the kind of system that brings together taxonomists, photographers and amateur entomologists. You can login, ask questions, obtain papers, identifications and so on. Today, I came across this entirely curious case of what can only be called "fly falconry" - check it out !


Monday, January 17, 2011


I am interested in a little mystery - the origin of the term "Jatinga bird mystery". It would be unpardonable if a scientist coined that term, for there is hardly any mystery in the entire matter nor is it specific to that location. It might of course have been a way of getting tourists or obtaining funds for misguided research.

The first time I heard the phrase was when still at school. One evening there was a documentary screening  at  the Indian Institute of Science Gymkhana and the question was asked by a student and posed to an old man named Salim Ali who had just woken up from a nap for the entire duration of the screening of  a documentary  (about Bharatpur - and remember that it was a time when TV penetration was low and Doordarshan was dull) and I do not remember hearing a cogent answer. One interpretation was that the birds were "committing suicide" in Jatinga (that was also a time when there were Disney films  with Lemmings committing suicide and neither Snopes nor Dawkinism existed) !  Fortunately the government website today seems to be slightly more enlightened and points out that the locals kill the birds after confusing them with lights on foggy nights. There is still some mystery mongering, perhaps aimed at tourists, as a last word on their page though.

Punch. January 11, 1879. p. 11

All this came to mind, strangely enough, while browsing through some ancient digitized versions of Punch Magazine (thanks as always to the Internet Archive). It is quite a challenge to imagine the conditions of that time and identify the humour  in those brilliant cartoons. Some of them can still be thought provoking, for instance - how does one evaluate the consequences of new technology. It is easy to dismiss cautions when  the predictions such as those of the early Luddites and technophobes are hyped. So exactly how did lights affect birds? It seems like very little is known in the Indian context. The numerous lighthouses around the country must be trapping a range of birds during their migration and numerous birds must be dying there. Perhaps some qualified organization will find a way to communicate with the  government bodies that control lighthouses and actually find out how many birds are disoriented or killed. Jones and Francis (2003) note deaths of up to 2000 birds in a night at a single lighthouse. There are a number of factors that contribute to increased mortality, including cloud cover, bad weather and phase of the moon. Apparently fewer mortalities occur towards the full moon. Birds are also attracted and killed at flares on offshore oil rigs. The use of green and blue coloured lights may reduce the number of bird mortalities. (More here )

Luminous fungal colonies (via Earth3D 1.0.5)
What could an excess of light at night do to humans? Probably hard to do controlled experiments but work on mice shows that they can become obese. Anyway the people who have been most affected by light are the astronomers. The only country in the world to apparently have an advanced light pollution law is Chile and this is led mainly by the large number of astronomical observatories in the region. Light pollution standards may also exist in Australia and the Czech Republic includes light pollution prevention in its law on protection of the air ! (Teikari 2007) The picture of the world by night makes it clear that many countries need better management of their lights. Like sound and noise, light pollution is probably a lot tougher to control as its effects are not obvious or readily visible. Worse still is that almost everyone is an offender.

So make sure you switch off those lights early tonight. Good night.

Further reading

Since writing this, I have found some rather old references to the use of lights in trapping birds.
Lanciatoia, an Italian hunting method
"In the south of Spain the practice of taking Larks and other little birds with bell and lantern supplies the markets with myriads of small fry. Mr Abel Chapman has referred me to his charming work, "Wild Spain", in which he says that the engines of the fowler are the "Cencerro" or cattle-bell and the dark lantern. "As most cattle carry the ' Cencerro' around their necks, the sound of the bells at close quarters by night causes no alarm to the ground birds. The bird-catcher, with his bright candle gleaming before its reflector and the cattle-bell jingling at his wrist, prowls nightly over the stubbles and wastes in search of the roosting birds. Any number of bewildered victims can thus be gathered, for Larks and such like birds fall into a helpless state of panic when once focussed in the bright rays of the lantern". There was a time in "Merrie England" when the right of catching Larks by such means was so highly valued as to be restricted in practice to the owners of land. The title of "Low-belling" was employed to distinguish this variety of fowling from other methods. (Macpherson HA (1897). A history of fowling. Edinburgh: David Douglas. p. 60)
Fowling at night from a book edited by A. Philippo Gallaeo with art by Jan Van der Straet [=Joannes Stradanus] (1596) Venationes   Ferarum,   Avium, Piscium. A copy of this treatise on hunting can be found on the wonderful French digital library

Post-postscript (20 February 2011)
While reading a book on the origins of phrases, I discovered that the phrase "beating about the bush" comes from the old practice of bat-fowling. The trappers who went at night were accompanied by those with long sticks who beat about the bushes to put the birds to flight.

19 September 2018 - larks were apparently also captured with mirrors!
Forty thousand larks are delivered in London every day for table purposes. Quite as many more are sacrificed for the sake of their feathers. And how are they caught? Smearing the branches of trees with lime, if slow, is an easy way of catching birds. A revolving mirror worked in the sunlight from behind a thick bush attracts all birds. They fly against it, are stunned, go to rest on neighbouring trees, the branches of which are limed; and the rest is easy. Another trick is to release a bird with a long limed rope attached to it. When others approach this birds (says the London Mail) they also become captives. This stuffed owl is thickly limed all over, and small birds that come to mock it cannot detach themselves from its feathers. - Dundee Evening Post 20 January 1903 p. 6