The poem as I know it:
The Cuckoo comes in April
She sings her song in May
She changes her tune
In the month of June
And July she flies away
Not unheard of to hear the Cuckoo in February, but more usually April as the poem. We were hearing Cuckoo's very late, into July, last year. The bird is very significant to country folk, the cider barrel's tapped when its first heard!