American robin eggs are blue to blend with natural surrounds.
© George Harrison
Gourmet jelly beans can come with the same speckled or mottled colors found on the eggs of some bird species.
© Brandon Dilbeck
This is the time of year when eggs are turning up everywhere— in Easter baskets for many, not too mention in bird nests across the country too.
With all these eggs around, it’s easy to take them for granted.
While we tend to not talk much about bird nests at eNature.com because we just don’t want to encourage folks to disturb nesting birds, eggs are actually very specialized objects and full of remarkable stories.
For instance, ever wonder why birds lay eggs of different colors and shapes?
There’s a good reason for just about everything we encounter in nature and, as you’d expect, eggs are no exception.
Why are do eggs come in colors? 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 colors, speckles or spots on them are camouflage. This also explains why birds that nest in cavities often lay all white eggs. They can’t be seen even when the parent birds are not sitting on them.
Why do the shapes of bird eggs vary? Again, to protect them. 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.
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 often 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 notable exception is the barn owl, which begins 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.
And as for jelly-beans and their shape… they too have evolved. According to at least one cultural historian, jelly beans appear to have become more egg-shaped and less bean-shaped over the years as the candy, thought to have first been created around the time of the Civil War, has become more associated with Easter and children’s Easter baskets.
Have a favorite fact or anecdote about nesting birds you’d like to share? Add it to our comments section below!