It is the female, however, that does the damage. Once mated she will lay 20 or more eggs, depositing them one at a time in the nests of unwitting hosts, and simultaneously stealing one of the host's own eggs, which she eats. To give her a clear run, her mate causes a disturbance, which lures the host away from base for a few vital seconds.
Depending on habitat, the female generally targets four species, all much smaller than herself: hedge sparrow, meadow pipit, pied wagtail and reed warbler. Her eggs vary from greyish-white to greeny-blue and brown, with a scattering of spots, and mimic the eggs of the host.
When the interloper chick hatches, after only 12 or 13 days, it grows so fast that it can soon push other chicks and unhatched eggs over the side of the nest. It then claims its foster-parents' full attention, and eats as much food as three or four of their own offspring would have put away, before it flies the nest when only three weeks old.Reuse content