Washington, July 16 : Ever wondered how birds spot cuckoos' eggs in their nests. Well, Czech researcher Marcel Honza says that their ability to see UV wavelengths helps them with this task.
Researcher from the Academy of Sciences of the Czech Republic set out to determine what enables black caps, a kind of European warbler, to tell whether an egg in their nest is from another bird.
The researchers found that the pattern of reflected UV light, which humans can't see, underpins the bird's ability to distinguish impostor eggs from their own.
Instead of testing the birds' reaction to real cuckoo eggs, the researchers introduced some abandoned blackcap eggs as impostors.
Some of the impostor eggs were coated in UV blocker, while some in Vaseline so that their UV reflectivity would not change.
The nesting parents accepted 11 of the 16 eggs coated in Vaseline.
However, it was a different matter for the birds sitting on UV-block-coated impostors because 17 brooding parents evicted the strange looking egg, pecking at the shell until they had made a large enough hole to stick their beak in, and carry it away.
Only 11 blackcaps accepted the interloper with its altered appearance.
Based on their observations, the researchers came to the conclusion that the UV appearance of the eggs was very important in enabling the blackcaps to recognise the new eggs as impostors.
Reporting the new finding in The Journal of of Experimental Biology, Honza said that the next step in the research would be to see whether cuckoos try to outsmart their victims by choosing clutches that closely match their own eggs' UV reflectivity.