The ovum produced by a bluebird sometimes displays a pale blue hue. This coloration is a defining attribute of the species’ reproductive output, distinguishing it from the eggs of many different avian species. Variations in shell pigmentation can happen, leading to eggs showing extra greenish-blue or, not often, even white.
This particular pigmentation performs a job in camouflage throughout the nest, probably providing safety from predators. Moreover, the consistency of this coloration throughout the species aids in identification and species recognition. Traditionally, the distinctive shade has been famous in ornithological research and subject guides as a key identifier of bluebird nests.
