Going by the letter of the law (and regulations), you can only use captive bred pigeons for training dogs.

The next question asked will be: "How can you tell if the pigeons are captive bred?" And the answer is.....I have no idea. Maybe feral pigeons are tougher than captive bred and they fight back?

And generally if pigeons are sitting on your roof, car or whatever leaving their calling cards they could be considered a nuisance. In Will's case on the family farm they can create problems with grain, cattle feed, etc. There's no shortage of them.