Pigeon (The Veil)

According to the records kept by the Veil, on the 83rd day of the 235th year the Veil and the Twelfth Doctor spent inside the confession dial, a pigeon somehow made its way into the castle; when the Doctor asked if "there [were] birds here", a commotion up in the rafters answered him. Neither inhabitant of the dial ever saw the pigeon again, nor figured out where it had come from. (PROSE: The Veil)