Jap Bluebird eggs are sometimes a pale sky blue, typically with a slight greenish tint. Often, they are often white, which is believed to be because of an absence of the pigment biliverdin. This attribute blue colour is a defining function of the species, readily distinguishing their nests from these of different birds.
The distinct coloration serves a number of functions. For ornithologists and birdwatchers, it aids in species identification and nest monitoring. The pale colour might also have evolutionary advantages, doubtlessly camouflaging the eggs towards the nest lining or reflecting daylight to stop overheating. Learning egg coloration contributes to a broader understanding of avian biology, together with genetics, evolution, and breeding habits. Traditionally, pure dyes mimicking this distinctive hue have been prized.
