The first X-ray movies of birds in flight have revealed the function of the wishbone: It's a spring.
Scientists who made the discovery suspect that the flexible, V-shaped bone helps birds breathe while they fly. Bird experts had assumed that the bone was simply a strut between the shoulders.
Farish A. Jenkins Jr. of Harvard University and colleagues Kenneth P. Dial of Harvard and George E. Goslow Jr. of Northern Arizona University took X-ray films of starlings flying in place against 20-45 m.p.h. winds in a wind tunnel.
In a report in the journal Science, the team described the way the wishbone bends each time a bird flaps its wings. "The wishbone turns out to be a spring," Jenkins said in an interview. At rest, the upper ends of the starling's wishbone are 11 or 12 millimeters apart. But when the wings descend, that distance stretches to 18 to 20 millimeters.