Numerous lineages of paravians were experimenting with different modes of flight through the Late Jurassic and Early Cretaceous. ~ Michael Benton et al
While wings ultimately developed to afford being entirely airborne, even early gliders gained aerodynamic benefits. Most flying animals, whether insect or bird, are close to the ground or water when taking off. The surface acts as an aerodynamic mirror, increasing pressure underneath the wing, interrupting downwash, and suppressing wing tip vortices’ turbulence. This aerodynamic interaction lowers the energy required for lift by 29%. Early evolved birds flapping their wings would have been able to run and jump swifter even if they never left the ground.
The biodiversity of these small, bird-like dinosaurs was incredible. ~ Belgian paleontologist Pascal Godefroit