How the Cuckoo Wages an 'Evolutionary Arms Race'

Clever birds figure out how to trick others into raising their kids

ByABC News
June 29, 2014, 10:11 AM
A common Cuckoo chick in Reed Wablers nest waits to be fed with its mouth wide open, in this undated file photo.
A common Cuckoo chick in Reed Wablers nest waits to be fed with its mouth wide open, in this undated file photo.
Getty Images

— -- There's nothing stupid about the cuckoo bird. It's a nasty cheat that sometimes leaves its eggs in another bird's nest so someone else can raise its chicks, and it is one of nature's best performers of trickery and deceit, but it's definitely not stupid.

Some members of this family of about 142 species are engaged in what scientists are calling an "evolutionary arms race" to see which birds can outwit the others.

Evolutionary biologist Mary Caswell Stoddard of Harvard University and colleagues Rebecca Kilner and Christopher Town of the University of Cambridge have found that some cuckoos have developed the ability to produce eggs that are a perfect match for the eggs produced by other members of the family. That's to convince the host that the foreign eggs really are hers so she won't toss them out of the nest.

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But meanwhile, some prospective hosts have figured out how to produce eggs that are distinctly different, even from eggs laid by other members of the family, so they will quickly recognize any uninvited guests.

"The ability of common cuckoos to mimic the appearance of many of their hosts' eggs has been known for centuries," Stoddard said in releasing the study, published in the journal Nature Communications. "The astonishing finding here is that hosts can fight back against cuckoo mimicry by evolving highly recognizable patterns on their own eggs, just like a bank might insert watermarks on its currency to deter counterfeiters."

Other researchers have found that cuckoos are more sensitive to incredibly subtle differences in colors, so the mimicry has to be right on target to work. You or I wouldn't be able to tell the difference between the host's eggs and those left behind by an interloper.

The scientists used the latest in recognition technology from computer science to find out how eggs can differ in ways so finely tuned that even a mother won't be sure which ones are hers.

The technology, which they call NaturePatternMatch, can detect differences in patterns that are far too subtle for us to see. It's based on the face recognition technology that allows a computer to determine if a person is really who he or she claims to be, which is useful in situations that demand the highest level of security.

The researchers are primarily interested in evolution as a whole, not just among cuckoos, and they found that these birds "have evolved effective signatures in diverse ways," so there are apparently many ways that an organism can master deceit.

But to be fair, not all cuckoos are cheats, and they aren't crazy. The name "cuckoo" comes from the sound it makes, not its IQ or quirky lifestyle.

Many old world species commonly engage in parasitic practices throughout Europe, Asia and Africa, but most species found in North America do what we tend to think all birds do, nurture and raise their own kids.

One of the best known cuckoos in the U.S. is the greater roadrunner, seen throughout the deserts of the Southwest. Like many cuckoos, it will sometimes enjoy a salad, but it loves meat and to some species it is the most feared predator on the planet. But despite its reputation as a killer, both the male and female parents share the responsibilities of caring for their brood.