Cracked! Riddle of egg shapes

A BIRD’S flying ability helps determine the shape of its eggs, say researchers.

The best fliers tend to lay eggs that are more ‘pointy’ or elliptical, rather than rounded, they found.

Various theories have been put forward to explain the huge variation in the shape of birds’ eggs. But after studying 49,175 eggs from 1,400 species, the scientists believe that egg shape and flying ability may have evolved together because of the need to keep an airborne body sleek and streamlined.

This reduced the size of the abdominal cavity, but to create enough room for healthy chick development, nature designed eggs that maximise internal volume without increasing their width.

One of the researchers, Dr Joseph Tobias, of Imperial College London, said: ‘Variation in the size and shape of eggs is not random but is related to differences in ecology, particularly the extent to which each species is designed for strong and streamlined flight.’