Complex sentence: This is especially true for the "Ancer indicus", whose migratory route, from Central Asia to India and back, causes it to fly over the Himalayas twice a year, a feat which makes it fly higher than any known bird.
Split into simpler sentences: This is especially true for the "Ancer indicus", whose migratory route from Central Asia to India and back, forces it to fly over the Himalayas twice a year. A feat which makes it fly higher than any known bird.