Scientists believe they know why birds' eggs are different shapes. Some eggs are quite round; some are kind of potato-shaped; and others are longer and pointy. Two thousand years ago, the Greek philosopher Aristotle said flatter eggs had female chicks inside them and rounder eggs contained male chicks. But he was wrong. A new study from Princeton University in the USA suggests that the shape of the egg depends on how well and how fast the female bird flies. Professor Mary Stoddard said: "It has not gone unnoticed that birds have evolved to lay eggs with shapes that are quite diverse in form - everything from a spherical owl egg to a pointy sandpiper egg."
Professor Stoddard and her colleagues created a mathematical formula to map the shape of different eggs. They looked at almost 50,000 eggs from 1,400 different bird species. The researchers put the shape, length and height of the eggs into a computer database. They also looked at how oval the eggs were. The researchers found that the birds that laid the most-oval-shaped eggs were the best fliers. Professor Stoddard said: "We were shocked to see that one of the best explanations for egg shape variation was flight ability." The researchers found that hummingbirds and sandpipers laid the most-oval-shaped eggs; owls laid the roundest eggs; and sea birds laid the pointiest eggs.
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科学家相信他们知道了为何鸟蛋形状各异。一些鸟蛋非常圆，一些鸟蛋像土豆，还有一些又长又尖 。2000年前，希腊哲学家亚里士多德表示，较扁平的鸟蛋里是雌性的小鸟，较圆的鸟蛋里是雄性的小鸟 。但是他错了 。来自美国普林斯顿大学的一项最新研究认为，鸟蛋的形状取决于雌鸟飞行的技能和速度 。Mary Stoddard教授表示：“人们一直都注意到，鸟下的蛋形状各异，从球形的猫头鹰蛋到尖尖的矶鹬蛋 。”
Stoddard教授和她的同事创建了一个数学模型来描绘不同的蛋。他们查看了1400种不同鸟类的近5万枚蛋 。研究人员把这些鸟蛋的形状，长度和高度存入电脑数据库 。他们还看了这些鸟蛋的椭圆度 。研究人员发现，最会飞行的鸟下的蛋最椭圆 。Stoddard教授表示：“我们很震惊地发现，鸟蛋形状不同的最好的解释就是飞行能力 。”研究人员发现，蜂鸟和矶鹬下的蛋形状是最椭圆的；鹰下的蛋形状是最圆的；海鸟下的蛋形状是最尖的 。