I wonder how they do that.
Do they raise a pigeon in one place, train it to return home, and then parachute it into resistance forces? Then those people have to keep the pigeon around until they want to send a message?
Wouldn't a pigeon attract attention? I suspect that if someone started keeping pigeons around the authorities would figure that out or someone would tell them. A pigeon isn't the most discreet critter to have around.
When I think about it using pigeons seems to be awkward.
Of course they could drop the one-time pad at the same time the deliver the pigeon, so that part would be practical.
Then they must have to send three or four pigeons to make sure one gets through.