You made a series of very poor, and often times very strange, decisions while you attempted to care for a very vulnerable animal. The baby bird entered your life very swiftly. It also left your life very swiftly.
Perhaps it is not right to pass judgment on your poor judgment, but it seems it would be safe to say that you are, at the very least, somewhat responsible for killing a tiny creature. After all, you left a rock on it while you went outside.
Then you desecrated its corpse.
Maybe you had the best intentions.
Maybe you thought the dirt was magical and could revive the tiny being.
We might never know.