Common cuckoo (Cuculus canorus) in flight. This is an adult male: Grey morph adult females have a pinkish-buff or buff background to the barring and the sides of the neck, and sometimes small rufous ...

Every cuckoo is an adopted child -- raised by foster parents, into whose nest the cuckoo mother smuggled her egg. The cuckoo mother is aided in this subterfuge by her resemblance to a bird of prey.