An interesting new study by V. B. Baliga, I. Szabo, D. L. Altshuler entitled Range of motion in the avian wing is strongly associated with flight behavior and body mass suggests that rather than the shape of a birds wing per se it is the range of motion in the elbow and wrist joints that determine how a bird swims though the air. Some birds glide smoothly like a bald eagle while other can hover like a hummingbird and this paper suggest range of motion in the joint is the key. A interesting read for those who are interested both in biomechanics and evolutionary biology.

You can find a short summary in Science Daily here.