Bird migration a mystery
We are very much attracted towards the world of birds which is full of fascination. We have always had the curiosity to know more and more about them. Travelling or migration is one of the greatest mysteries of bird life. Every year thousands of birds migrate from their native land to some warmer places. This can be seen in the northern regions of Asia, Europe and America from where they travel to the warmer southern lands. During spring, they come back to their homeland.
The birds are punctual. They may get delayed due to some reasons such as weather. The exact day of their returning may be calculated. When everything is normal, they come back as soon as the winter season ends.
Some species of birds also travel short distances mainly in search of food. Some birds also move from one place to another due to the hardships of living there. We can notice this type of migration in Northern India where there are great differences in seasons. But a certain amount of migration is one of the common characteristics of the birds which are confined local movement.
In India, it is a common phenomenon when during the summer some of the birds go to the higher regions of the mountains and return to the lower foothills or plains in winter, because the Himalayas and the Gangetic plains lie close to each other.
While travelling long distances, birds have to face various difficulties and hardships. As they have to pass through hills, forests, mountains and long stretches of water, at times they are caught in great storms. Sometimes they are driven out of their due courses and are drowned in the wild waves. At night they get confused due to bright city lights.
Migrating birds generally fly at their normal speed which is usually from 48 kmph to 64 kmph. It very rarely exceeds 80 kmph. Small birds seldom exceed 48 kmph. Most shorebirds fly between 64 kmph and 80 kmph while many ducks travel at 80-96 kmph. Migrating bids do not generally fly very high. They normally fly at the height of 900 meters, but some of the birds have been found at greater heights too.
Some of the birds fly long distances at a stretch even without taking a pause to rest and feed, while others cover distances in stages stopping to rest on the way. Some fly by the day only, some both by day night.
Birds usually like to move in flocks. We are very much attracted towards the V-shaped formation of flying of cranes in the sky. Some of the birds like swallow flycatchers, warblers, shorebirds and water birds first flocks of the birds like swallow, flycatchers the sky enjoying their company.
The detailed information about the birds is gained by ringing and observing the habits of the birds. Ringing is a method in which a young adult bird is capture and one puts on to its leg a light band of metal or plastic which a number, date identification mark and the address to which finder is requested to return the ring. The bird is then set free. The place where the ringed bird is shot, captured or found dead gives a clue to the direction and locality to which the bird has migrated.
It is proved by ringing that birds cover long distance during their migratory movement which is generally north to south in winter and vice –versa during spring. We have some evidence that the woodcock flies a distance of 2400 km from the Himalayas to the Nilgiris without a pause. The wild ducks come here from Central Asia and Siberia covering a distance of 3200 km to 4800 km over the Himalayas some storks come over from as far as West Germany.
Willow warbler, the smallest of all and half size of a sparrow flies a long distance of 3200 km too reach here every winter. The spring movement of the bird is due to the availability of nesting sites.
The migration of birds is really an interesting study and there is still much to be known, such as how a bird decides when to start. How does it know the locality? These are a few such questions which are to be solved.