Which bird lays its eggs in the nests of other birds?

The cuckoo lays its eggs in the nests of other birds. This behavior is called brood parasitism: instead of building a nest and raising its own chicks, a female cuckoo places an egg in a host bird’s nest and leaves the host to incubate and feed it.

The best-known example is the common cuckoo of Europe and Asia. Its usual hosts include dunnocks, meadow pipits, and reed warblers. The cuckoo chick often hatches before the host’s young and may push their eggs or nestlings over the edge, allowing it to receive all the food brought by the foster parents.

Cuckoo parasitism is an evolutionary arms race. Some females lay eggs that closely resemble the host’s eggs, while host birds may recognize and eject suspicious eggs. Cuckoo eggs also tend to have unusually strong shells, which helps them survive being dropped into a nest.

Not every cuckoo species is parasitic; many build and care for their own nests. That is why “cuckoo” is the standard quiz answer, but the more precise statement is that several cuckoo species—not the entire family—use brood parasitism.