Scientists expose true extent of cuckoo's cunning

September 4, 2017

Common cuckoo. Credit: Wikipedia/GFDL 1.2
The common cuckoo, notorious for evading parental duty by hiding her eggs in the nests of other brooding birds, is even more devious than previously thought, scientists revealed on Monday.

After laying an egg, the female distracts the owner of the nest—a reed in this case—essentially by frightening the poor bird out of its wits, they said.

The cuckoo gives a "chuckle" that mimmicks the call of the sparrowhawk—which loves to snack on warbler flesh—before abandoning her egg among the warbler's clutch and flying off to freedom.

"This hawk-like chuckle call increases the success of parasitism by diverting host parents' attention away from the clutch and towards their own safety," a duo of Cambridge University researchers wrote in the journal Nature Ecology & Evolution.

"As a result, the female cuckoo might have 'the last laugh' in this particular battle."

The bird whose behaviour gave us the word "cuckoldry", is an example of a "brood parasite"—birds, insects or fish that trick others into raising their young.

This is often at the expense of the foster parents' own offspring.

To avoid getting caught—which will lead to the imposter egg being kicked out of the nest—the cuckoo has developed some nifty tricks, including matching its egg colouring to that of its target, for camouflage.

The bird has also adopted "remarkable secrecy and speed" in depositing its egg, said the team.

For this reason, scientists have battled to understand why the cuckoo would risk exposure by "chuckling" so soon after committing its crime.


The Cambridge team theorised the purpose was to distract the warbler with fear.

To test this, they played the recorded calls of male and female cuckoos, a sparrowhawk, and a random, non-threatening bird—a collared dove, to reed warblers.

Only the male cuckoo makes the signature sound copied in pendulum clocks. The female utters a laughter-like "kwik-kwik-kwik" not dissimilar in frequency to the sparrowhawk's "kiii-kiii-kiii".

The warblers, they observed, reacted with the same vigilance to female cuckoo calls as to hawk calls, and diverted attention away from their clutch.

The warblers ignored male cuckoo and collared dove calls.

In a further test, the team played the female cuckoo call to tits— which are also eaten by sparrowhawks but are not targeted by cuckoos for fostering duties.

In tits, too, "cuckoo calls increased vigilance as much as hawk calls" even though cuckoos pose no threat, said the team.

This suggested that both tits and warblers mistook the female cuckoo call for that of a sparrowhawk, they concluded, even though the two sound quite different to the human ear.

"Our results show that the female enhances her success by manipulating a fundamental trade-off... between clutch- and self-protection," the authors concluded.

Explore further: Neighborhood watch and more: How reed warblers watch out when there's a cuckoo about

More information: Female cuckoo calls misdirect host defences towards the wrong enemy, Nature Ecology & Evolution (2017).

Related Stories

Cuckoo tricks to beat the neighborhood watch

August 2, 2012

To minimise the chance of being recognised and thus attacked by the birds they are trying to parasitize, female cuckoos have evolved different guises. The new research, funded by the Natural Environment Research Council, ...

Birds' strategic mobbing fends off parasitic invaders

January 29, 2009

Reed warblers use mobbing as a front line of nest defense against parasitic cuckoos, according to a new report published online on January 29th in Current Biology, a Cell Press publication. Cuckoos act as parasites by laying ...

Birds use social learning to enhance nest defense

June 4, 2009

Reed warblers live with the threat that a cuckoo bird will infiltrate their nest, remove one of their eggs, and replace it with the cuckoo's own. This 'parasitism' enables the cuckoo to have its young raised by unsuspecting ...

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.