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Ask a Redbird Scholar: Why are bird eggs different colors?

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Why are bird eggs different colors?

image of Angelo Capparella

Associate Professor Angelo Capparella

The adaptive significance of different egg colors has long been a subject of hypotheses in ornithology, and there are likely many reasons for different colors and patterns. One reason for the varying colors of eggs is obviously camouflage when they are in a nest potentially visible to predators. Most cavity nesting birds lay all white eggs, whereas most other birds lay pigmented eggs. Another reason for pigmented eggs is to recognize parasitism via egg dumping by other bird species that have laid eggs into their nest in hopes that the host will raise their young.

For colonially nesting birds, there are subtle differences in patterns that probably allow parents to recognize their own eggs among a plethora of nests. Additionally, it is likely that different pigments regulate light levels reaching the embryo and could have effects ranging from protection against ultraviolet light to providing cues for embryonic development.

There are still other hypotheses showing that this mystery needs more probing to attain full understanding. The mystery deepened last year as it was discovered that the eggs of those dinosaurs closely related to birds had a diversity of colors, meaning birds apparently inherited this ability from their dinosaur ancestors, thereby begging the question of the original functions of this adaptation.

Angelo Capparella, associate professor, School of Biological Sciences

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