Zoologger: colour tricks help put a cuckoo in the nest

Species: Cuculus Canorus
Habitat: Summers in Northern Eurasia, confusing warblers

Let's face it, child rearing isn't for everyone. Midnight diaper changes, a seriously compromised social life, and trading in the two-seater coupe for a mid-size sedan can be too much for some of us to handle.

Readers who find themselves in this category might be reassured to know there's at least one other creature on the planet that is, in all likelihood, even more keen to shirk parental responsibility.

The common cuckoo is notorious for pawning off its young on other birds, like the Eurasian Reed Warbler (Acrocephalus scirpaceus). Unfortunately for these more willing caregivers, the cuckoo is a ruthless parasite. Upon hatching, young cuckoos push their surrogate brothers and sisters from the nest, leaving the unsuspecting host with a single cuckoo chick rather than a brood of its own.

For obvious reasons, reed warblers have never been happy with the arrangement. They will attack female cuckoos on sight, reducing the chance of their nest being targeted. However, the sly cuckoo has developed an innovative way to avoid hostilities. Female cuckoos have evolved two different guises to minimise the chance of being recognised and attacked by warblers.

True colours

It's unusual for female birds of a single species to come in different colours, but the phenomenon is surprisingly common for female cuckoos. Some are brownish-red, while others have grey, hawk-like plumage that deters other birds from attacking them.

Rose Thorogood of the University of Cambridge says researchers have long been puzzled by the colour difference, so her team designed an experiment to see if they could find a reason for the anomaly.

At their study site in the UK, they placed balsa wood models of female cuckoos, with either grey or brown feathers, next to a reed warbler nest. The warblers began to mob the model ? and their neighbours from nearby nests learned to join the attack to a lesser degree. When the researchers then moved the model cuckoo nearer to one of those neighbouring nests, the warblers at that nest ramped up their attacks on the model.

But this was not the case if, during the move, the researchers switched a grey cuckoo for a brown one, or vice versa. When Thorogood and her colleagues did this, the birds at the new nest continued to attack the model at the same low frequency as when the cuckoo model was closer to their neighbours' nest.

Tricky evolution

Thorogood says the study suggests a reason for the cuckoo's different colours. The warblers apparently learn from social experience within the nesting group to watch out for cuckoos of one particular colour ? but they are then less responsive to a cuckoo of a different colour.

"Lots of animals and insects have been shown to gather information from watching others," Thorogood says. "What we didn't know was that this was actually useful in defending oneself, but at the same time it can help your enemy to develop new tricks."

Journal reference: Science, DOI: 10.1126/science.1220759

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

Have your say

Only subscribers may leave comments on this article. Please log in.

Only personal subscribers may leave comments on this article

Subscribe now to comment.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

If you are having a technical problem posting a comment, please contact technical support.

Source: http://feeds.newscientist.com/c/749/f/10897/s/2206971d/l/0L0Snewscientist0N0Carticle0Cdn221380Ezoologger0Ecolour0Etricks0Ehelp0Eput0Ea0Ecuckoo0Ein0Ethe0Enest0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

bloom energy franklin graham jambalaya taylor swift and zac efron basketball wives manny ramirez easter 2012