We know birds come in many sizes and shapes, so it’s no surprise that their eggs would too. It has been speculated in the past that egg shape could be linked to making incubation more efficient. Aristotle theorized that long, pointed eggs are female while more rounded eggs are male. Other theories were tied to environment such as cliff-dwelling birds lay conical eggs that roll in tight circles, so as to not drop out of the nest.
A new Study offers a Simpler Explanation
Evolutionary biologist Mary Caswell Stoddard of Princeton University and her team examined more than 49,000 eggs from 1,400 different bird species and classified them by shape. Stoddard and her colleagues wrote a computer program, Eggxtractor, that examines an egg in any picture and measures its length, width, and shape.
“We are able to look at the egg in many dimensions and crack the mystery,” Stoddard says/puns.
The answer surprised her. “Egg shape appears to be related to flight ability in birds,” she says.
It made sense though, she goes on to say. Birds that evolved for powerful or long-distance flight needed a body to match: sleeker, more streamlined.