Call them "qucks" and "duails."

With a little egg tinkering, scientists replaced a duck's flat bill with a quail's pointy beak, breeding some funny-looking birds.

But the experiment yielded more than an avian oddity. It uncovered some of the key cellular players in bird evolution and more importantly, may lead to a better understanding of what causes facial birth defects such as cleft palate.

Figuring out why birds have such an amazing variety of beak styles is integral to the study of evolution. One of Charles Darwin's most famous observations during his 1835 visit to the Galapagos Islands was that finches were subtly different including their beak size and type depending on where they lived on the chain of pristine, volcanic islands. His analysis of such differences later led to his theory of evolution through natural selection.

But just what genes and cells are behind those differences remained mysterious.

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