Birds identify eggs by 'colour'

Avians are more intelligent than you ever thought -- they use colour to identify the eggs of 'parasite' birds, such as cuckoos, from their own and eject them from their nests, a new study has revealed.

Researchers in Australia have found that birds have the ability to recognise small changes, particularly in the ultraviolet wavelengths, which helps them in distinguishing between their own eggs and eggs of other birds.

According to lead researcher Dr Mark Hauber of the University of Auckland, "Birds have very different visual senses to humans, for example they can see ultraviolet wavelengths where we cannot.

"Those birds which parasitically introduce their eggs into the nest of other birds dramatically increase the amount of time and energy needed to provision the nest.

"Our research shows that the peculiar abilities of birds to perceive broad-spectrum colour is vital to recognise their own eggs, and can identify small differences as well as wavelengths that humans wouldn't be able to distinguish."

In their study, the researchers introduced eggs into the nests of song thrushes in Australia and New Zealand, painted in a range of colours close to the birds' own eggs.

They found that the birds ejected eggs of different colours from their nests, particularly those with differences in reflecting ultraviolet or short (blue) wavelength light, the 'Biology Letters' journal reported.

The research was conducted in collaboration with the University of Birmingham in Britain and Palacky University in the Czech Republic.