Cracking the mystery of egg shape

In addition to these theories, scientists also thought that precocial baby birds—those that are usually mobile and more mature at birth, like ducks—had asymmetrical eggs because the blunt ends have more pores, letting in more oxygen to help their brains develop faster. After crunching the numbers, the scientists found the links they’d been looking for: the length of an egg correlates with bird body size. And the stronger a bird’s flight, the more asymmetrical or elliptical its eggs will be.

Source: vis.sciencemag.org