The Mystery of the Hanging Pigeon

There is a hanged pigeon outside my window. I take no joy in this. Evidence seems inconclusive to me as far as cause of death. Accidental? Maybe it got caught in this plastic bag and then hooked on the fence. Murder? A trap? Dinner?

UPDATE: I climbed up and freed the bird, also getting what I believe to be an answer to the primary question. Any guesses?