Skip Navigation

Species Search:

Birding Focus: Interesting stories of our feathered friends.

American robin eggs are blue to blend with natural surrounds.
© George H. Harrison

The Incredible Egg

Ever wonder why birds lay eggs of different colors and shapes? There is a good reason for everything in nature and eggs are no exception. Birds’ eggs are colored for protective reasons. The parent birds that incubate them are not always on the nest covering them, and at those times, the eggs are exposed to predators. The color, speckles or spots on them are camouflage. That explains why birds that nest in cavities lay all white eggs. They can’t be seen even when the parent birds are not sitting on them.

Why are birds’ eggs shaped differently? Again, to protect them. Birds that nest on cliffs, like seabirds for example, have eggs that are smaller at one end than at the other. This is to make them roll in a circle and not fall off the cliff. Birds with round eggs, build deep nests that keep them from rolling out.

How do baby birds hatch? They have a so-called “egg tooth” on the top of their upper mandible, which cuts through the egg shell when it is time for them to come out. The egg tooth falls off soon after hatching. Why do the eggs in a nest all hatch at about the same time? Because most birds lay an egg a day, but do not begin incubating them until the last egg is laid. One exception are barn owls that begin incubation with the laying of the first egg. That’s why the youngsters in a brood range in size and age from the oldest to the youngest.

-- George H. Harrison