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There are two variants of female cuckoos: a gray morph that looks like a sparrowhawk, and a rufous morph.

If, for example, there are many sparrowhawk-like cuckoos or many sparrowhawks, the host birds learn over time to distinguish whether the bird in front of them is a sparrowhawk or a cuckoo.

“We found a similar relationship where we had black sparrowhawk nestlings in the more urbanized part of Cape Town actually having what we considered a more intense immune response,” says Nwaogu.

One theory is that the flutes were used attract the birds of prey - namely the Eurasian Sparrowhawk and the Common Kestrel - to frighten waterfowl, making them easier to catch.

According to the findings published in the Nature Science Report journal, one of the theories suggests hunters positioned near the waterfowl used the flutes to imitate the call of birds of prey, especially the Eurasian Sparrowhawk and the Common Kestrel.