A crow will never be a dove.
More Bulgarian Proverbs:
The village feeds the town.Bulgarian
Dead horses can't kick.
Bulgarian
You are permitted in times of great danger to walk with the devil until you have crossed the bridge.
Bulgarian
God is not without sins: He created the world.
Bulgarian
He who breaks his word shall through his word be broken.
Bulgarian
Grapes do not grow in a willow tree.
Bulgarian