ИСТИНА

Cuckoos, Cuculus canorus and C. optatus, are a brood parasite which tricks other species of birds into caring for its eggs and chicks.During breeding season there is a change of two types of begging signals for both cuckoo species. After leaving a nest chicks started to produce calls of fledgling and trill, that were produced in chicks excitement moments. Modified begging signal remain with grown chicks as a greeting signal in a moment of feeder man arriving.