With which popular traditions, tales, and legends is the cuckoo related in your country’s folklore?

Cuckoo – Wikipedia

In Europe, the cuckoo is associated with spring, and with cuckoldry, for example in Shakespeare‘s Love’s Labours Lost.

In fact, cuckold is derived from cuckoo.

In Greek, the cuckoldry association has not captured people’s imagination: that’s all about horns (presumably via deer). The proverbial expressions about cuckoos are quite unlike the associations the bird has in English:

Κούκος – Βικιπαίδεια:

• solitariness—cuckoos don’t have their own nest, being parasitic, but they also don’t spent a lot of time in the host nest they take over; hence, various variants of “lonely as a cuckoo”. Also, Τρεις κι ο κούκος “three plus a cuckoo” = “almost noone”, the cuckoo being the Greek equivalent of tumbleweeds. (Apparently there is an anticipation of this in Aristophanes, Acharnians 598.)
• cheapness, low quality, compared to a nightingale: Θα σου κοστίσει ο κούκος αηδόνι “A cuckoo will cost you a nightingale” (i.e. you will be ripped off)
• harbinger of spring: Ένας κούκος δεν φέρνει την άνοιξη “one cuckoo doesn’t bring spring” (as opposed to the more common “one swallow doesn’t make a summer”, which dates from Aesop)
• going silent (in summer): Βουβάθηκε σαν ο κούκος τ’ αϊ-Γιαννιού “he’s gone dumb like a cuckoo on St John’s Day” (24 June)