Full of Deceit and Murder, Cuckoos Reveal New Disguise

May 2, 2005

Cuckoos live what seem to be lives full of deception and murder. As adults, they lay their eggs in the nests of other birds. (Why raise your own chick, when you can dupe others into doing the work for you?)

Female cuckoos typically lay a single egg. When these interlopers hatch, they promptly push the other eggs out of the nest, killing the host birds' true offspring.

For the newborn cuckoo, masquerading as multiple chicks can be difficult, especially when the lone, giant nestling replaces the usual clamoring brood.

Scientists say an East Asian cuckoo species appears to have an ingenious way to fool foster parents into thinking that their own offspring are still alive and tweeting. The method helps the cuckoo chick secure the food supply it needs to satisfy its voracious appetite.

The suspected ruse, discovered by Japanese scientists, involves yellow patches on the chick's wings that, when the chick quivers its wings, create the illusion that there many more mouths to feed in the nest.

Researchers who discovered this clever adaptation describe the behavior in the current issue of the research journal Science.

"The display of the wing patch might simulate extra gapes [open beaks] and so stimulate increased provisioning," write Keita Tanaka and Keisuke Ueda, biologists at Rikkyo University in Tokyo, Japan.

Cuckoo expert Rebecca Kilner, a behavioral ecologist at Cambridge University in England, said the finding was incredible. "The researchers have uncovered a novel bit of natural history that's really wonderful and exciting," she added.

When feeding their own young, parent birds respond to a combination of vocal and visual begging signals to decide how often to bring their nestlings food. "The cuckoo's task, having killed the hosts' young, is to tune in to this system of parent-offspring communication," Kilner explained.

Cuckoo Deception

For a single cuckoo chick, it can be difficult to look like a full brood of a host species' nestlings. The European cuckoo uses vocal deception, employing extremely intense begging calls to secure the same amount of food that the host bird's own brood would have consumed.

"What's exciting about this Asian species of cuckoo is that it exploits the visual mode [of deception]," Kilner added. Such behavior has never been described before.

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