In this huge family, not only does each species have a different language, even cuckoos of the same species may sing different songs. Populations in different areas each have their own "mother tongue," so to solve this ancient mystery is not so easy.
這龐大的杜鵑科家族，不僅每一種有不同語言、單一種本身也有不同的叫聲，同一種杜鵑因為分佈地方不同，還有各自的「母語」，因此要解這千古懸案，想來也不太容易。