How Did Birds Learn to Fly?

Posted by
Rosemary Drisdelle
Jan 25, 2007

One explanation has it that the ancestors of today’s birds were theropods, carnivorous dinosaurs that chased their prey on two feet. These dinosaurs were apparently feathered but the feathers weren’t used for flight—they were probably to keep the animals warm in cold weather and cool when the temperature went up. Eventually, a combination of light weight (hollow bones), feathers, and running speed aided the evolution of flight.

Recent fossil evidence, however, supports a different theory—the theory that the first fliers were more like flying squirrels. Dinosaurs that climbed to heights in trees or on cliffs might have evolved an ability to glide to protect them if they fell. Fossils show that feathered dinosaurs had long feathers on their back legs as well as on their front limbs. Such an arrangement wouldn’t have worked well for an animal running on the ground.

Some birds, of course, have come full circle. Birds like the Dodo and the Kakapo migrated to islands where they had no predators and subsequently lost the ability to fly. For the Dodo it was a fatal loss; the fate of the Kakapo remains to be seen.