Agreed on why they didn’t tag it and let it go. I assume the found the bird incidentally during a drug bust.

Pigeon roosts can be surprisingly discreet in prisons, where there are often natural pigeon roosts anyway. And prisons are also where small amounts of contraband are worth using various methods like this to move them.

Drones are also effective, but prisons have been getting better at detecting and preventing drone drops. Very difficult to figure out which bird you’re supposed to shoot down though. Predatory birds can be used, but they don’t always grab the right pigeon, since you can’t train a hawk to distinguish which pigeon it should grab.