Scientists believe they know birds' eggs are different . Some eggs are round; some are kind of potato-shaped; and others are and pointy. Two thousand years ago, the Greek philosopher Aristotle said eggs had female chicks inside them and rounder eggs contained chicks. But he was wrong. A new study from Princeton University in the USA suggests that the shape of the egg depends on well and how fast the female bird flies. Professor Mary Stoddard said: "It has gone unnoticed that birds have evolved to [lay eggs with] shapes that are quite in form - everything from a owl egg to a pointy sandpiper egg."
Professor Stoddard and her created a mathematical to map the shape of different eggs. They looked at almost 50,000 eggs from 1,400 different bird . The researchers put the shape, length and height of the eggs into a database. They also looked at how oval the eggs were. The researchers found that the birds that laid the -oval-shaped eggs were the best . Professor Stoddard said: "We were to see that one of the best for egg shape variation was flight ." The researchers found that hummingbirds and sandpipers laid the most-oval-shaped eggs; owls laid the eggs; and sea birds laid the pointiest eggs.