Unpredictable egg scramble throws off parasitic parents

Some birds shirk their parental duties by slipping their eggs into other birds’ nests. But the birds that host the shysters’ eggs have a trick of their own — scrambling the looks of their eggs so they have distinct signatures.

Warbler species whose nests are infiltrated by the cuckoo finch and weaver species whose nests are invaded by the diederik cuckoo lay eggs with colors and markings that are individualistic and hard to mimic. Researchers report the finding in the July 7 Proceedings of the Royal Society B. Eggs of warbler and weaver species whose nests don’t get infiltrated don’t have the same degree of unpredictable patterns, suggesting that defenses against parasitic parents have evolved in the host species.