Scientists crack mystery of bird eggs' colour variation

Darker eggs may be at an advantage in colder regions as they are more heat-absorbent

Scientists have cracked the mystery of why bird eggs are different colours, with new research suggesting it boils down to temperature.

The appearance of bird eggs is rooted in two pigments, one of which is greenish and the other reddish-brown. Different concentrations of these pigments, together with the underlying white calcium carbonate of the shell, give rise to colours ranging from deep blue to greenish-white and rich brown.