Eggs that are left out in the open tend to have colors and patterns that help them blend in with their surroundings, while eggs that are always covered are more likely to be white.

Some bird species hide their eggs in other species’ nests for free caretaking. Pigment patterns (both visible and ultraviolet) may help parents discern their own eggs from those of the parasitic invaders.  

Bird egg colors come primarily from two pigments. Brownish-red colors come from protoporphyrins, and blue-green colors come from a pigment called biliverdin. The amount and mixture of each pigment on an egg produces a rainbow of possible colors.

Color is the finishing touch: As the egg passes through the female’s oviduct, pigments are secreted and stain it. Streaks form if the egg moves while the pigment is flowing, and spots occur if the egg stays still.

“No two eggs look exactly alike, and sometimes there can be great variation in egg color and pattern even within a single species.”

“Birds that lay eggs in precarious places often have pointy eggs. This way, the egg rolls in circles—and not off a cliff. Cavity-laying birds often have rounder eggs that pack well; they’re not in danger of rolling away.”

These vivid stripes are even bolder through an ultraviolet lens. Their shells are striking and appealing to us, but to this land snail’s predators, the pattern may work as camouflage or warning.