The parasitism of the cuckoo, expressed in the tossing of eggs and even hatched chicks by this bird into other people's nests, is one of the unsolved mysteries of nature. Interestingly, in cuckoos, already a few hours after birth, the so-called "throwing away" reflex appears in a foreign nest. While still blind, the chick, spreading its naked wings, crawls under the egg or chick of the lawful mistress of the nest and, laying it in the hollow on its back, throws it away.
Another curious feature of the cuckoo breed is the almost complete absence of a "voice" in the female cuckoo. Few probably know that the crowing in our forests, to which we are so accustomed, is the business of the male cuckoo. The female can only utter a not very audible "Kli-Kli-Kli".