New Delhi, May 22 -- When wood thrushes arrive in northern Mississippi on their spring migration and begin to serenade my neighbourhood with their ethereal, harmonised song, it's one of the great joys of the season. It's also a minor miracle. These small creatures have just flown more than 1,850 miles (3,000 kilometres), all the way from Central America.

Other birds undertake even longer journeys - the Swainson's thrush, for example, nests as far north as the boreal forests of Alaska and spends the nonbreeding season in northern South America, travelling up to 5,600 miles (9,000 kilometres) each way.

These stunning feats of travel are awe-inspiring, making it that much more tragic when they are cut short by a deadly collision with a gl...