Those adorable little birds with a distinctive sound. Perhaps NOT. I recently learnt that some species of Cuckoo cannot relate to the film "One flew over the Cuckoo's nest" Why, because building nests is far too much trouble. In fact looking after chicks is a bit of a bind as well. So they don't bother.
For some Cuckoo's it is far easier to lay your egg in the nest of a different species of bird, perhaps a small Reed Warbler.Then fly off and leave the rest to your psychotic chick. Yes the newly born chick is born with the first instinct to kick the real eggs out of the nest and relax waiting for food. The little Reed Warbler doesn't catch on. Perhaps the small parent bird wonders why the chick ends up twice her size and not as easy to please as her friends chicks? This is the stuff that inspires horror stories and films, it's The Changeling story straight from nature. Truly science is stranger than fiction.