The Common Cuckoo breeds in a unique way: it is an obligate brood parasite and never raises its own young.
Host nests: the female lays her eggs in other birds' nests, one egg per nest, and lets the host family do the rearing.
Specialisation: each female is a specialist on one host species and lays eggs that mimic the host's in size and pattern.
Rapid hatching: the cuckoo's egg has a shorter incubation period (11–12 days) than the host's eggs, so the cuckoo chick hatches first and pushes the others out.
In this way the Common Cuckoo avoids both nest-building and parental care, which makes it one of Europe's most studied birds.