But a pidgeon leaves a trail of metadata on the ground as it carries your message, so this communication channel is still vulnerable to bulk network analysis by some Advanced Persistent Threat.
Alternatively, you can just whitewash that threat vector away.
If it wasn't for the fact that it'd be tax funded I'd love to see them try bulk collection of that.
Trained Peregrine Falcon: Hold my beer.
Typical: we started with a technical problem, and started bikeshedding it, so now we have drunk falcons.
That'll give you a denial-of-pigeon attack, but does it really risk interception?
I guess The Man is why homing pigeons are extinct now.