The CIA has declassified a Cold War plan to train pigeons for spy missions inside the Soviet Union. Under the code name Tacana, the operation aimed to use pigeons to photograph sensitive sites behind the Iron Curtain, and tested whether tiny cameras could be strapped to the birds to automatically take photos. The pigeon has the unique ability to find its way hundreds of miles back home no matter where it was originally deposited. Because of this superpower, the humble pigeon has been used by humans for communications for thousands of years, and were first used for intelligence gathering during World War One. The newly declassified files also shows that the CIA tried to train ravens to drop bugging devices on window sills, and dolphins for aquatic surveillance. The CIA believed the animals could fulfill “unique” tasks for the agency.