The Ruppell's vulture, the highest-flying bird, can fly as high as 37,000 feet. The common crane and bar-headed goose have been observed flying over the Himalayas at heights of 33,000 feet and 29,000 feet, respectively.
The whooper swan flies at 27,000 feet. An alpine chough was observed at Mount Everest flying at 26,500 feet. Mallards have been seen as high as 24,000 feet high; one mallard struck a commercial airline in Nevada at 21,000 feet. Although these observations are commonly made by mountain climbers, high-flying birds are increasingly spotted by radar or airplane pilots. Nocturnal migrating birds, such as shorebirds, fly at night over the ocean at 15,000 to 20,000 feet, according to the Northern Prairie Wildlife Research Center. When migrating, the bar-tailed godwit flies at 20,000 feet, and the white stork flies at 16,000 feet.