The secret files are stored at the CIA’s headquarters in Langley, Virginia, is a museum, which is not open the general public.
The 1970s’ operation, codenamed Tacana, explored the use of pigeons with tiny cameras strapped to their bodies to automatically take photos, the newly released files show.
It took advantage of the fact that the humble pigeon can be dropped somewhere they have never been before andhave the amazing ability to find their way hundreds of miles back home.
The use of pigeons for communications dates back thousands of years but it was in World War One that they began to be used for intelligence gathering.
In World War Two a little known branch of British intelligence – MI14(d) – ran a Secret Pigeon Service which dropped birds in a container with a parachute over Occupied Europe.
A questionnaire was attached and more than 1,000 pigeons returned with messages including details of V1 rocket launch sites and German radar stations.