Sep 25, 2013 03:11 PM EDT By Russell Westerholm, UniversityHerald Reporter

New research suggests cuckoo finches will lay more than one egg in a victim's nest to trick the host parent into fostering their young for them, according to a press release.

Dr. Martin Stevens and Dr. Jolyon Troscianko, of the University of Exeter, and Dr. Claire Spottiswoode, of Cambridge University, co-authored the study, published online Tuesday in the journal Nature Communications.

The researchers found that the African cuckoo finch female will lay its eggs in the nest of an African tawny-flanked prinia host. When there are multiple eggs, the host parent cannot tell the fraudulent eggs apart from its own.

The research helped explain why female cuckoo finches often lay more than one egg in one host's nest. Female cuckoo finches likely do this because they can mimic nearly perfectly the eggs of its host parent. The bird probably developed this ability as host parents became more selective with the foreign eggs appearing in their nest and the rejection of those found to not be theirs.

The rejection of an egg, of course, depends on the parent's ability to determine their own egg from another's. The nest host must pick out various and small differences in its own egg and the imposter's. This is an excruciatingly important task because the risk of being wrong means they would be rejecting their own egg. It is a cognitive task that requires the parent to compare the eggs based on memory of what the egg looked like upon birthing.

The researchers determined the presence multiple fraudulent eggs causes enough doubt in the host parents' mind to make them not reject any eggs.

"Our work shows that by laying multiple eggs in each host nest, the cuckoo finch has evolved a novel strategy, in addition to egg mimicry, to defeat host defenses and increase its reproductive success," Stevens said. "Laying several eggs in a host nest causes confusion in host defenses, and when combined with effective mimicry, they can outwit the hosts and help more of their young to be reared."

Stevens speculated if maybe other animals had a similar strategy, or if host parents would develop a new way to combat the technique.

"In the future it would be great to know whether other brood parasites have similar strategies, and whether there is any way that hosts can fight back in the arms race against the cuckoo finch."

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