Most people are familiar with the typically plain white or brown eggs of the domestic chicken, Gallus gallus domesticus. However, with over 10,000 species of birds in the world, the size, coloration, and shape of their eggs varies almost as dramatically as the birds themselves. This showcase explores the coloration and patterns of eggs.
The pigment and markings of the eggs are created by glands in the female bird’s uterus and oviduct and are applied onto the egg as it passes through the reproductive system.
Some species have eggs that are uniform in color and are often white or blue. These eggs are common amongst cavity nesters (examples include kingfishers and owls), species with covered nests (ducks), and bird species that rarely leave their nests during the incubation period (pigeons).
Other bird eggs are two-toned or multicolored, and are typically speckled or scrawled. The patterns on these eggs may provide camouflage from predators or distinguishing marks for a parent bird to distinguish between individual eggs. New research indicates that in some species, the speckling may strengthen fragile eggs by providing an adhesive or additional coating over thinner portions of the shell. Speckled or scrawled eggs are commonly found among songbirds (cardinals and mockingbirds) and ground nesting birds whose eggs are often exposed (killdeer).