Why Are Robin Eggs Blue?

Robin eggs are blue due to a fascinating evolutionary adaptation that may help protect them from sun exposure. The blue pigmentation of robin eggs is primarily due to a pigment called biliverdin. This pigment moves through the robin’s bloodstream and is deposited on the eggshell as the mother robin lays the egg.

One of the main theories behind the blue coloration is that it helps protect the eggs from the harmful effects of sunlight. The blue pigment may act as a filter, reducing the amount of ultraviolet (UV) radiation that penetrates the eggshell. This is particularly important for robins, as their nests are often built in open areas where the eggs are exposed to direct sunlight. Interestingly, it is only American robins that produce blue eggs; the European species’ eggs are white.