That's in the module.
Nightingale is a singing-bird, without sin. He has a voice given him in his throat, to phrase God and gladden the heart of man.
Sparrow is a bad, spiteful bird. He's like a pickpocket in his ways. He doesn't like man to be happy.
OR YOU'RE ASKING TO WHOM IT CAN COMPARE.. I can compare it to GOD - NIGHTINGALE and MEN - SPARROW