Scientists crack mystery of bird eggs’ colour variation
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.
But what influences the appearance of the eggs that different birds lay has been a topic of hot debate, with theories including the need for camouflage from predators, mitigating the harmful effect of UV light on the embryo’s DNA, helping birds recognise which eggs are theirs – and even that different colours may have different antimicrobial properties.
Researchers say while these factors might still play a role – particularly at a local level – a key influence at a global scale is temperature.
“Eggs in these colder places are darker brown and then as you go towards the tropics and even the temperate zone there are just more competing selection pressures, so there is more variation in colours,” said Dr Daniel Hanley, a co-author of the study from Long Island University.