Enlarge / This reed warbler hasn’t cottoned on yet. (credit: Per Harald Olsen / Wikimedia Commons)
Cuckoos are nest parasites.

That means they lay eggs in the nests of other birds, which then put the effort into raising the chicks.
So you’d think they’d be quiet about it. Yet female cuckoos have a tendency to make a bubbly, chuckling call while they’re laying their eggs.

That’s a strange thing for them to do, because host birds aren’t too fond of cuckoos.
That chuckle doesn’t sound at all like the male cuckoo call.

But it does have similarities to the call of the sparrowhawk, which led researchers Jenny York and Nicholas Davies to wonder whether the call might be a purposeful deceit—a ruse to distract the hapless host birds while their nest is being violated. York and Davies’ paper in Nature Ecology & Evolution this week provides evidence that the cuckoo chuckle does indeed seem to distract host birds by making them fear a sparrowhawk attack.
Faking it
Plenty of species have evolved to mimic predators, often for their own protection.

For instance, the wasp beetle mimics a stinging wasp, causing predators to steer away.

Cuckoos seem to be a fan of that tactic: some cuckoo species look quite a bit like hawks, and this seems to protect them from mobbing by other birds.
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