Cracking the mystery of avian egg shape

A team of international scientists - including an archaeologist from the University of Bristol - have cracked the mystery of why bird eggs are shaped the way they are. According to the new research published today , egg shape in birds is related to adaptations for efficient flight and a mechanistic model reveals how different egg shapes may be formed. The eggs laid by birds come in an astonishing variety of shapes: ellipses in hummingbirds, spheres in owls, pointy ovoids in shorebirds and almost everything in between. Avian egg shape has fascinated humans for millennia - even Aristotle wrote about it - but we still lack the answer to this simple question: Why did different egg shapes evolve, and how? The answer - that egg shape is related to flight ability, and that the egg membrane may play a critical role in determining shape - is the surprising finding of this new study. The study's lead author Dr Mary Caswell Stoddard of Princeton University, explains: "In contrast to classic hypotheses, we discovered that flight may influence egg shape. Birds that are good fliers tend to lay asymmetric or elliptical eggs. In addition, we propose that the stretchy egg membrane, not the hard shell, is responsible for generating the diversity of egg shapes we see in nature." To unravel the mystery of egg shape, an international team of researchers used a multi-step, multidisciplinary process, applying tools from computer science, comparative biology, mathematics and biophysics.