Researchers found that the bar-tailed godwit, one of the world's longest flying non-stop migratory birds, shrinks its digestive organs boosting endurance and optimising flying. Research published in 'Frontiers in Ecology and Evolution' said change in body boosts the capacity of the bird's exercise organs. Godwits fly around 12,000 to 13,000 km in September and October to Australia and New Zealand.