Washington: Just like a bank might insert watermarks on its currency to deter counterfeiters, many birds have evolved signature patterns on their eggs in order to distinguish them from those laid by a Cuckoo cheat, said a study.
Many birds are affected by the parasitic Common Cuckoo which lays its lethal offspring in other birds` nests.
"The ability of Common Cuckoos to mimic the appearance of many of their hosts` eggs has been known for centuries," said Mary Caswell Stoddard from Harvard University in the US.
"The astonishing finding here is that hosts can fight back against cuckoo mimicry by evolving highly recognisable patterns on their own eggs, just like a bank might insert watermarks on its currency to deter counterfeiters," Caswell added.
Using a new computer vision tool called NaturePatternMatch, researchers studied the pigmentation patterns on hundreds of eggs laid by eight different bird species (hosts) targeted by the Common Cuckoo.
They discovered that some hosts, like the Brambling, have evolved highly recognisable egg patterns characterised by distinctive blotches and markings.
Some host species have evolved egg patterns that are highly repeatable within a single clutch, while other species have evolved eggs with patterns that differ dramatically from female-to-female in a population.
Still other host species produce egg patterns with high visual complexity.
Each strategy is effective, increasing the likelihood that a given host will identify and reject a foreign egg.
"Some species use two of these strategies, but none uses all three," explained Rebecca Kilner, professor from University of Cambridge in Britain.
"A signature like this would be too complex to be easily recognised," Kilner added.