Nazi
Homing Pigeons
Homing pigeons were used by both the Axis and the Allies as vehicles for transporting messages back home in World War Two. No scholar is quite certain exactly how these pigeons, often called racing pigeons, are able to find their way back to their place of birth, but in a similar manner to how salmon spawn, pigeons always return to a certain spot. This has obvious wartime consequences, as both sides used the pigeons to relay information that the other side would not be able to intercept.
British youth may know the story of Paddy the Pigeon after a tour at Bletcheley Park, but what they may not know is that Nazi Germany had a pigeon program in place as well. Recently released documents from MI5 have shown that Hitler was very interested in the possibility of using pigeons as a wartime asset, and named SS henchman Heinrich Himmler (left) as President of the German National Pigeon Society, commissioning all German Pigeons to spy for the Nazis.
After numerous Britons noticed pigeons flying towards the general direction of France early in 1942, the Army Pigeon Special Service developed a program to end the exodus.
Realizing that fire must be met with fire, the British
Anti-Pigeon forces developed and trained Peregrine falcons (right) 
to
take down pigeons as they flew away from the British coast. The falcons were highly effective, as
they were fast (flying up to speeds of 200 mph) and efficient, able to survey much
more land than any human could.
While never shown for certain, it was speculated that German pigeons were dropped off on the British coastline via parachutes, U-boats, powerboats, and/or as personal baggage. The pigeons were then housed by spies, and sent back to Germany along with sensitive messages.
(images from http://news.bbc.co.uk/1/hi/special_report/1999/01/99/wartime_spies/263333.stm)