Why eggs are in different shapes?

Eggs come in different shapes. Some eggs, like those of hens and sea birds, are round at one end and pointy at the other- this is called an ovoid shape. Other birds like ostriches lay eggs that are perfectly round, while pigeons lay eggs that are pointy at both ends. The explanation for this difference in shape lies in the number of eggs that birds of different species lay at one time, and the type and place of their nests. Birds that nest on cliffs, such as many seabirds, tend to have eggs that are smaller at one end than at the other. This is to make them roll in a circle, and less likely to fall off the cliff. Birds with round eggs, usually build deep nests that keep them from rolling out. In addition, eggs take on a particular together for warmth during incubation. An egg with an ovoid shape is also a lot more comfortable for a bird to lay than, say, one that is a sphere or a cylinder. Whatever its shape, eggs are incredibly strong- try craking one by squeezing your fingers evenly over itm and you will realize how tough an egg is !