Bar-headed geese that fly across the Himalaya in long-distance migrations every year have been the focus of attention for high altitude scientists who have wondered how come they can fly over the mountains with almost effortless ease with so little oxygen while humans are so completely exhausted while climbing.

The geese start their journey from Siberia and fly into Mongolia after which they wing their way to the Qinghai Province, in the northern part of the Tibetan plateau where large flocks can be seen in the high altitude lakes. From here they fly south over the Himalaya and reach Rajasthan, some flying d own as far as Tamil Nadu. Recently these birds have been known to carry the deadly H5N1 Avian influenza virus.

In 2000, scientists attached a radio collar on a bar-headed goose and tracked it via satellite as it flew from the Bharatpur Wildlife Reserve in north India, across western Nepal up to the Tibetan plateau, crossing three countries. The bird rode the jetstream, flying more than 500km from near New Delhi, overflew Dhangadi, Jumla, across the "hump" at above 7,000 m to lakes in Tibet: a non-stop night flight lasting 16 hours and 30 minutes.

What is known about the ability of the geese to fly at extremely high altitudes is that their haemoglobin (the protein that carries oxygen in the blood) is built more efficiently for oxygen carriage at very high altitudes. In addition their blood flow to the muscles is characterised by a dense network of capillaries that is conducive to better oxygen delivery to the tissues.

Much of their efficiency in flying over these extreme altitudes is shrouded in mystery. Besides efficient oxygen usage and energy expenditure, do they have a unique genetic advantage that explains it all? Correctly interpreting the physiological mechanisms that help these birds deal with low oxygen environments may in the long run help human beings in intensive care units who suffer from diseases like COPD ( chronic obstructive pulmonary disease) and ischemic heart disease that lead to similar hypoxic (low oxygen) conditions. Finally, understanding their efficiency at high altitude may also give us some important clues about better ways to utilize oxygen while climbing in the high Himalayas.

See also:
Bird country, ALOK TUMBAHANGPHEY
Feathered friends, PAAVAN MATHEMA