Unpredictable egg scramble throws off parasitic parents

eggs with patterns

Eggs from Cisticolidae warblers reveal that those from species whose nests have been infiltrated by cuckoo finches have extremely complicated markings compared with those from species whose nests have not been invaded.

Caves et al/Proc. B 2015 (CC BY 4.0)

Some sneaky birds like to 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.

A look at warbler species, whose nests are infiltrated by the cuckoo finch, and weaver species, whose nests are invaded by the diederik cuckoo, shows that these host birds can lay eggs with colors and markings that are individualistic and hard for parasitic cuckoos to mimic, researchers report June 17 in the Proceedings of the Royal Society B. Eggs of similar bird 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 these host birds.

photo of Ashley Yeager

Ashley Yeager is the associate news editor at Science News. She has worked at The Scientist, the Simons Foundation, Duke University and the W.M. Keck Observatory, and was the web producer for Science News from 2013 to 2015. She has a bachelor’s degree in journalism from the University of Tennessee, Knoxville, and a master’s degree in science writing from MIT.

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