(St.). April 14th. The cuckoo sings from St. Tiburtius's Day (April 14th) to St. John's Day (June 24th).
This most certainly is not correct, as I have heard the cuckoo even in August: but without doubt July is the month of its migration generally.
The proverb says:
“July, prepares to fly: August, go he must.”
It is said that he migrates to Egypt.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894