Flight of the Goose

by Anushree Bhattacharjee

Flying high, at speeds of over 150 kilometers per hour, crossing the Himalayas in one single tireless flight! Flapping strongly and honking over the highest mountain range in the world! No, this is not a story about Superman. This is about a “Superbird”, the Bar-headed Goose ( Anser indicus ), one of the highest flying birds in the world. In India, the Bar-headed Goose is found to breed near lakes in the cold desert region of Ladakh. In the rest of the country, the bird is a winter migrant, spreading as far south as Kanyakumari.

Not just a pretty face

A beautiful pale grey goose, easily distinguished from other species of geese by the characteristic black bars on its head that gives the species its name, the Bar-headed Goose hardly looks the part of a super-athlete. However, researchers found Bar-headed Geese tagged with GPS transmitters had completed migration journeys of up to 8000 kilometers in approximately two months, which involved crossing the world’s tallest mountain ranges, the Himalayas twice! Although the birds made frequent stops during their journey, they seemed to be crossing the Himalayas in one continuous stretch of approximately eight hours of flight. A similar physical exertion with no time for acclimatization would simply kill a human.

How do they do it?

Most birds make use of good tailwinds for take-offs and depend on thermal updrafts for soaring and gliding. The Bar-headed Goose is a rare exception relying only on vigorous flapping of its wings. It chooses to ignore the day-time tailwinds making its sharp ascents at night or during early morning hours when the air is relatively calm. Researchers believe the cooler and denser air may be allowing the birds to generate a stronger lift-off while also helping regulate body heat.

Expert adaptation

The Bar-headed Goose’s wing area is slightly larger than other geese of its size. It has a large heart that can beat extremely fast. The haemoglobin in its blood is able to accommodate higher amounts of oxygen, which allows it to breathe more efficiently as it flies over high altitudes. Bigger and stronger lungs and a dense network of blood capillaries which surround the flight muscles help the bird to sustain better oxygen flow throughout its body. The geese have more red blood cells and more capillaries in their body while their flight muscles have more mitochondria – energy producing structures present inside the cells.The Bar-headed Goose also has the ability to hyperventilate (breathe excessively hard and fast) without any physiological ramifications, thus increasing the amount of oxygen entering the blood stream. The strong flapping of wings generates body heat which is retained in the down feathers and helps prevent ice from building up on the wings.

 Look and learn

It is believed that a better understanding of the physiology of this species may help develop drugs for people with respiratory diseases.

Photo credit: Kalyan Varma