New examinations of modern bird flight suggests the "where" is not so important as the "how." Scientists closely measured the wing beats of a kind of quail-like bird called chukars. These birds take flight by stroking their wings at a precise angle. What's more, even hatchlings that can't fly with their short, undeveloped wings flap at this same angle.
The researchers conclude that flight mechanics—just how birds flap their wings and fly—was more important than whether they first learned to glide. Once the proper wing-stroke was learned, flight could have occurred from ground or tree.
Illustration by Robert Petty