Why Do Bird Eggs Have Different Shapes?
Look to the WingsIn the most comprehensive study of egg shapes to date, scientists say that the best predictor of long or pointy eggs is a bird’s flying ability.
By STEPH YIN JUNE 22, 2017
The New York Times
Owls’ are spherical, hummingbirds’ are elliptical and sandpipers’ are pointy.
All bird eggs have the same function — to protect and nourish a growing chick. But they come in a brilliant array of shapes. This variety has puzzled biologists for centuries. Now, in the most comprehensive study of egg shapes to date, published Thursday in Science, a team of scientists seems to have found an answer.
The researchers cataloged the natural variation of egg shapes across 1,400 bird species, created a mathematical model to explain that variation, and then looked for connections between egg shape and many key traits of birds. On a global scale, the authors found, one of the best predictors of egg shape is flight ability, with strong fliers tending to lay long or pointy eggs.
“This paper is remarkable because it creates a wonderfully unified theory for the variety of egg shapes we see in nature,” said Claire Spottiswoode, a bird ecologist at the University of Cambridge and the University of Cape Town who did not participate in the research.