“One of the more unusual (but still fascinating) exhibitions at Bletchley Park is all about the role pigeons have played in the First and Second World Wars. Aircrews used them as rudimentary black boxes, writing their coordinates on a message and releasing the pigeon if they had to ditch or crash land.

There was also a cull of birds-of-prey all along the south coast during World War Two to ensure the pigeons could get back safely.”

- Garrett Coakley

(via Method of wrapping carrier pigeons for dropping from air-craft | How to be a Retronaut)