Some abilities that animals posses are truly amazing and astonishing. Pigeons are one of such animals which are surprisingly smart and most of us people who are living in the era of e-mails and mobile phones can't believe that one or two centuries ago pigeons were used as very reliable "postmen". They were used to send the letters to the most unreachable places but this vintage photos of pigeons reveal us that they were also used as tools for espionage activities.

This rare collection of pigeon photography contains some amazing photos which were taken from air by cameras that were attached to pigeons. [source]