As winter sets in, millions of birds leave their nests in the northern hemisphere and head towards warmer lands in the south. During spring, they once again wing their way back to their original nesting grounds. This yearly ritual is known as migration.
While some birds are great travellers, flying from one country to another; others merely flap down from the high mountains to sheltered valleys for the winter. The Arctic tern (of North America) is the hardiest traveller of all. Each year, these birds fly as far south as Antarctica and back, covering a mind-boggling distance of 29,000 kms.
Most migratory birds travel along well-defined flight paths that often follow either the coastline or the sea currents. Research shows that birds who migrate by day judge direction by the angle of the sun, while night travellers steer by star patterns. But the actual manner by which the birds convert what they see, into navigational aids, remains a mystery.
Migratory birds often suffer drastic losses en route – while some fall prey to predators, others die of exhaustion. American wildlife experts are now attempting a unique experiment, which they hope will establish a safe (and easier) migration route for endangered whooping cranes.
A distinctive long-necked bird with a white body, black wing tips and a red crown, the whooping crane stands about 4.5 feet tall and has a 6.5-foot wingspan. It is the tallest North American bird.
It is estimated that there are barely 411 whooping cranes left (of which only one migratory flock exists, moving between the Northwest areas of Canada and USA). Experts say another migratory flock is needed to ensure the crane’s survival in the wild.
However, instead of risking experimentation with whooping cranes, scientists have chosen a species of cranes, called sandhill cranes, which are plentiful and have similar characteristics to whooping cranes.
These sandhill cranes are ordinary birds with a slight modification in their upbringing – they have been hatched and raised with aircraft noise constantly in the background. A pilot is leading a flock of sandhill cranes as they wing their way from the eastern US state of Wisconsin to the south-eastern state of Florida. (Believe it or not, but the pilot is dressed to look like a giant crane and bird puppets are attached to the aircraft).
Cranes fly in a V formation to conserve energy. Except for the bird right in front; each bird in the formation gets an added push from the air currents created by the bird ahead. With a plane leading the way, the cranes are still flying in a V-formation with the flock leader flapping close to the plane’s wingtip – close enough get a push from the air currents generated by the plane.
If the experiment succeeds, and the sandhill cranes cover the 1,500 km-long migration route, it could help establish a migratory flock of rare whooping cranes in the eastern United States too.