哪种鸟和喷气式客机飞得一样高(图)

飞的像大型喷气式客机一样高的鸟

　　What bird flies as high as a jumbo jet?

　　2008---2009学年 第1期

　　Jet streams are high-altitude rivers of freezing air that flow about 30,000 feet (48,280 km) above sea level. Moving at more than 200 miles per hour (322 kilometers per hour), the air in jet streams contains only two-thirds as much oxygen as air at sea level.

　　Bar-headed geese, the avian world's highest-flying migrants, regularly fly in jet streams, a place where normally only jumbo jets dare to venture. Powerful flappers, the bar-heads are well adapted for flying over the Himalayas when migrating from feeding grounds in India to breeding grounds in Mongolia.

　　Bar-heads have specialized hemoglobin that extracts oxygen from rarified air more quickly than that in other birds. Like all birds, they can pant for long periods without constricting blood vessels in the brain, which allows them to stay mentally focused during long commutes.

　　Capable of flying about 50 mph (80.5 km/hr) under normal conditions, bar-heads using jet-stream tailwinds can speed along at 100 mph (161 km/hr). Flapping wings generate body heat that helps keep the birds warm in the freezing air.