Whilst most birds fly below 4,900 feet (1,500 metres) above sea level, some species can fly much higher. On 29 November, 1973, over Abidjan (Ivory Coast), a bird was sruck by an airliner at more than 36,700 feet (11,200 metres). The bird in question was a Rüppell’s vulture, named after the Explorer and German zoologist, Eduard Rüppell (1794-1884). The incident is rare because this species of vulture does not habitually fly at such high altitudes. The most likely hypothesis is that it had been taken aloft by an ascending air current.
Nevertheless, there is another bird capable of flying at high altitudes of up to 33,000 feet (10,000 metres), called the Bar-headed goose, recognizable by its white head adorned with two black bars, hence its name (see photo). The species breeds in Central Asia, and during its migration between Mongolia and India, overflies the Himalayas (Everest rises to 29,000 ft / 8,8 metres). A feat that only the Demoiselle Crane can match according to David Bismuth, President of ornithomedia.
To fly at high altitude, where oxygen is scarce and atmospheric pressure low, Mother Nature has provided Bar-headed geese with unique physiological capabilities. They have, for example, greater lung capacity than other birds, and also a more extensive vascular system to transport the richer red blood cell containing blood. Bar-headed geese also hyperventilate, without side effects, which in turn increases the amount of oxygen in their blood. Finally, their muscles contain more mitochondria, the organelles or structures that provide cells with energy. All of which allows these birds to fly as high as they do. There are about 60,000 Bar-headed geese in the world.