Birds identify ‘rogue’ eggs by their colour

July 4th, 2008 - 8:45 pm ICT by IANS  

Washington, July 4 (IANS) The cuckoo is notorious for fooling other birds into hatching its eggs, but there are birds that have the ability to catch them out. According to a new study, song thrushes have the ability to identify the eggs of “rogue” species like cuckoos in their own nests.

Auckland University researchers placed eggs in song thrushes’ nests, painted to resemble their own. But the birds ejected the “foreign” eggs, particularly those with differences in reflecting ultraviolet or short-wavelength light.

“Birds have very different visual senses. For example, they can see ultraviolet wavelengths where we cannot,” said Mark Hauber, who led the study.

“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 they can identify small differences and wavelengths that humans wouldn’t be able to distinguish.”

The findings of the study have been published in the online edition of the journal Biology Letters.

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