This video from Britain says about itself:
BTO Bird ID – Cuckoos
13 April 2016
Cuckoos are well-known birds, but their distinctive and eagerly awaited song can be confused with several other species. Despite their popularity, Cuckoos are rarely seen and, when they are, can easily be mistaken for a bird of prey. Let us help you pick out this iconic bird that was once believed to turn into a Sparrowhawk in the winter – neatly explaining its silence and disappearance outside the breeding season.