The blue colour in robin eggs is due to biliverdin, a pigment deposited on the eggshell when the female lays the eggs. There is some evidence that higher biliverdin levels indicate a healthier female and brighter blue eggs. Eggs laid by a healthier female seemed to encourage males to take more interest in their young.

What colour eggs do Robins lay?

Why are robins' eggs blue? American robins' eggs are blue due to a pigment called biliverdin, which is deposited on the eggshell when the eggs are laid. Biliverdin is a green bile pigment and is the same pigment that causes some bruises to initially look bluey-green.

What type of bird lays little blue eggs?

House Finches lay eggs that are bluish-green, and sometimes use a nestbox. See more photos. Starlings also lay blue eggs, but they are bigger than bluebird eggs. About 4-5% of bluebirds actually lay white eggs.