Historical account of bird migration

The earliest of this puzzlement dates back to the time of the Greek polymath Aristotle.

A flock of Black-headed gulls, a bird that breeds way up North, reached Kathmandu valley last week. Thousands of birds from over 150 species call Nepal home or use it as a stopover site during the winter migration season. The migration of Demoiselle crane and Bar-headed geese, which takes them above the mighty Himalayas, has puzzled many scientists and naturalists. Sir Edmund Hilary, in his book High Adventure , mentions observing birds above Mount Everest during the ascent towards the summit.