The egg

Robin's eggs

Which came first: the chicken or the egg? The first egg-laying reptiles, distant relatives of birds, showed up about 280 million years ago. The tough leathery eggshell was great—it kept water in and everything else out. The first real birds came along about 150 million years ago. So the answer is, the egg came first.

Eggs are strong. They have to be. They have to support the weight of an adult bird sitting on them. An ostrich egg, for instance, must support the weight of the male ostrich, who can weigh 350 pounds! 

The important thing about egg size is how big is the egg relative to the size of the mother. A mother ostrich weighs 50 times more than the egg. A mother hummingbird weighs 8 times more than her egg. Relatively speaking, hummingbirds have bigger eggs than ostriches! In these terms, the biggest egg of all belongs to the New Zealand Kiwi. The kiwi weighs only 4 times more than her egg. In people terms, that would be like a 60-pound child laying an egg as big as a watermelon!

Hummingbird's eggs

The last step in egg production is the addition of the color. Robins lay eggs with a distinctive blue color; the flightless emu lays dull green eggs that turn a shiny black in a few days. The Northern Flicker lays eggs covered with mysterious-looking brown scribble marks. Owls, woodpeckers and hummingbirds lay white eggs; blackbirds and gulls, speckled eggs. Blue and green colors come from bile pigments. Reds, blacks and browns come from the breakdown of red-blood cells. Speckled eggs are for camouflage. Owls lay white eggs that show up well in the dark; this may prevent the mother from trampling them accidentally. No one really knows why robins' eggs are blue.

Egg notes:

• Six-year-old Thomas Edison tried sitting on the eggs of the family goose. He thought he could get them to hatch faster. It didn't work.
• Here is an old superstition: "A person who finds an egg with two yolks should make a wish while eating it."
• Ancient Greeks used ash of eggshells mixed with wine as toothpaste.