Robin Eggs

While checking in on how spruce tips are developing, I stumbled upon a robin's nest filled with its beautiful blue eggs.

Have you ever wondered why robin's eggs are blue? I sure have.

One of the purposes of eggshell colour is protection from light. Darker colours prevent the penetration of harmful ultraviolet (UV) radiation, however it will also absorb heat from the sun (like the dark car effect), which can damage an undeveloped chick. Lighter colours will absorb less heat but have less protection from UV radiation.

Birds will evolve to produce their egg colour depending on their habitat. If they nest in more exposed locations, eggs will have a lighter colour, while those birds that nest in covered areas like robins in the forest, will have darker coloured eggs.

The blue tones are made by the bile pigment biliverdin, that is deposited in the shell as the egg is being formed. This pigment is also responsible for the blue-green colour seen in moths and butterflies.

In humans, biliverdin results from the breakdown of heme, a component of our red blood cells. It can be seen briefly as bruises in their initial stage when they are greenish, until biliverdin breaks down into bilirubin making a yellowish colour.

Dr. Cristina Allen ND