Narrator: This is Science Today. A new theory on the evolution of bird flight suggests advanced parental skills led former ground-dwelling reptiles to the trees where they could better nurture their young. James Carey, an ecologist at the University of California, Davis, says until now, there have been two basic theories on the evolution of bird flight: the cursorial, or ground-to-tree theory and the arboreal, or tree-to-ground model.
Carey: My feeling was that neither one of these theories really rang true. I decided to look into the evolution of birds and when I got in this literature, it's basically contrasting what's the difference between reptiles and birds - and that is that the first impression would be that birds can fly and virtually no reptiles can.
Narrator: Carey proposes that the evolution of feathers was linked to parental care, as was the beak.
Carey: Out of all the literature, including the theories of the arborial and cursorial theory, the beak has been ignored. Basically, advanced parental care involves provisioning with a point source. The beak is basically a point source for provisioning food to the young.
Narrator: For Science Today, I'm Larissa Branin.