Bird eggs come in a range of curious markings and colours. Both the robin and song thrush lay stunningly vibrant blue eggs, the cormorant's are an understated mint green, chickens lay rusty, red-brown eggs and the emu produces one of the largest eggs, a rich green-black beauty. But do these colours serve a purpose? Some eggs shells are designed to help camouflage them from predators, while others signal their overall quality. Lately, scientists have determined that there may be another reason – heat.
After plotting data from 634 species of birds on a map of the world, researchers found that darker eggs trend towards colder climates. Much like dark shingles on the roof of a house, darker eggs absorb more heat from the sun, allowing the birds to adapt to the cold. “In the Arctic, parents have to go out to forage and get back to their eggs quickly,” says researcher Daniel Hanley of Long Island University. “If you can buy them five extra minutes, that can actually be really beneficial.” I can’t help but think about the number of people who wear dark coats during the winter here in Canada. Perhaps, inadvertently, humans are doing the very same thing.