Sumer is icumen in,
Lhude sing cuccu!
Groweth sed, and bloweth med,
And springeth the wude nu -
Sing cuccu!

Awe bleteth after lomb,
Lhouth after calve cu;
Bulluc sterteth, bucke verteth,
Murie sing cuccu!

Cuccu, cuccu, well singes thu, cuccu!
Ne swike thu naver nu;
Sing cuccu, nu, sing cuccu,
Sing cuccu, sing cuccu, nu!

Anonymous Olde English

http://www.poemhunter.com/poem/cuckoo-song-4/