Which birds can fly at great heights?

* Bar-headed goose (Anser indicus): Found in the Himalayas, this bird has been recorded flying over Mount Everest at altitudes of over 8,800 meters (29,000 feet).

* Great frigatebird (Fregata minor): This seabird can soar to altitudes of over 4,000 meters (13,000 feet) in search of food.

* Common crane (Grus grus): These birds migrate over the Himalayas and have been recorded flying at altitudes of over 6,000 meters (20,000 feet).

* White stork (Ciconia ciconia): These birds migrate long distances and have been recorded flying at altitudes of over 3,000 meters (10,000 feet).

* Trumpeter swan (Cygnus buccinator): These birds migrate over the Rocky Mountains and have been recorded flying at altitudes of over 2,000 meters (6,000 feet).