How do birds learn to fly? To catch fish? To fly on a specific migratory path? These and several such questions have been floating around in my head for a while. And I have not had enough time to research and figure them out. A few weeks back, while on a trip to Ladakh, I came across an interesting behaviour that made me dig a little deeper into one of these and I learnt a few things as I did.
We had checked out of where we were staying at Spangmik and the plan was to drive along the Pangong Tso, turn off to Chushul and then head onwards to Hanle. We must have been about 30 mins down the road along the edge of the Pangong when we spotted some activity and got off the road. We saw some Common Terns and Brown-headed Gulls flying along the edge of the lake and since they were against the light, we decided to walk around to align ourself better. While we were tracking the Common Terns we noticed one of the sub-adults doing something interesting.
Initially, we all thought that he had managed to snag a fish and were all straining to get some images of the bird with its catch. Looking through the viewfinder, I realised that it was not a fish in its beak but a stick (or maybe a reed). And he was doing something very interesting. He would fly with the reed in his beak, hover at a point, drop the stick into the water, wait for it to sink, dive in to pick the stick and then fly around in a circle to repeat this all over again. Maybe somewhere during this routine he would be looking for approval from the adults around (ok, ok, I just made that up).
He did repeat this a few times and we had enough chances to try and get the entire sequence. I have converted some of these into a slideshow which captures this entire sequence better than a series of images would.
I couldn’t really find any research that talks about this kind of behaviour but I managed to come across a few interesting articles that give me a clue to explaining what we saw.
Firstly, I reckon that the brains of birds are constantly-learning neural networks and they teach themselves to catch fish based on past successes or failures. There is no research that shows that these birds are trained to fish by their parents. Maybe, the instinct to fish is genetically hard-coded and they learn to become efficient at it through practise and learning – practise makes perfect probably applies here.
Secondly, birds that catch fish need to learn to account for refraction. And need to figure out the angle of attack and its correlation to the refraction compensation. This is also something that they learn by practise / experience. Which is probably why, there is enough data to show that the strike-rate (or kill-rate if you please) of Juvenile / sub-adult Eagles and Ospreys is much lower than adults. Check this link out for an interesting project around Ospreys. That (the lower strike-rate) is probably why the sub-adults are larger in many Eagles than the adults – their larger wings gives them a larger range to compensate for a lower kill-efficiency. This was an interesting link which has some behaviour research around eagles learning to hunt.
If you come across any other explanations to how birds learn, do send them over to me. Till then, I will stick with my ‘practice makes perfect’ theory.