I had a similar experience once. Raven. Roof. Tap, tap, tapping. I spent 5 years in the military and, after a while, in dawned on me that the tapping sounded like Morse Code. I grabbed a pencil and piece of paper:
-.. --- / -.-- --- ..- / .... .- ...- . / .- -. -.-- / -- .- -.-- --- -. -. .- .. ... . ..--..
Do you know what that translates into?
"Do you have any mayonnaise?"
Alas, I did not. But I tapped back that I had some mustard. He never came back.