Cuckoos Don’t Sneak Into Other Birds’ Nests—They Barge Right In

Cuckoos don’t just make other bird’s raise their young, they lay their eggs while the other bird is in the nest

Great Spotted Cuckoo Marion Vollborn/ BIA/Minden Pictures/Corbis

Cuckoo birds aren’t just the inspiration for intricate clocks. They’re also shameless parasites. Brood parasites, that is. Many species of cuckoos have been known to leave their eggs in other birds’ nests, letting their young be raised by entirely different species. Scientists used to think that cuckoos would simply wait for the opportune moment (when the original parent was out of the nest or distracted) to lay their eggs, but it turns out that cuckoos are way more brazen than that. 

In a new study in the journal Ethology, researchers from the University of Granada found that the Great Spotted Cuckoo laid its eggs in the nests of magpies while the magpie was sitting on the nest. 

The scientists think that magpies, as a species, had just gotten sick of raising these ungrateful cuckoo birds and started sitting on their nests almost constantly while they were incubating their own eggs. This defensive measure isn’t working out well for them, though. In this particular game of Darwin-esque brinkmanship, the cuckoo basically decided to call the magpie’s bluff and go for the crazy (cuckoo, if you will) option, laying eggs in another bird’s nest while the bird was still sitting there. 

That’s not to say the magpies aren’t fighting back. In almost all cases that the scientists recorded, the magpies attacked the intruding cuckoo, with violent pecking, but it just wasn’t enough. In every single instance, the cuckoo accomplished her mission and laid her eggs. 

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