Fly The Coop Meaning

(of a bird) To escape from a pen or similar enclosure.

Example: 1910, William MacLeod Raine, A Texas Ranger, ch. 3:
  Not liking the accommodations, I took the first chance and flew the coop.
1961 Jan. 6, "Assisi Revisited," Time:
  Explained a Curtiz assistant: "We had three ravens in Assisi; one died of cold, and another flew the coop."