Interesting thread - for several reasons (discussion about pellet rifles, what will or won't perforate a tin roof, even hunting pigeons.
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But have you considered trapping the pigeons? From time to time I've read about doing that from survivalists, or exterminators. Use a recangular shaped (metal most likely) trap with hang-down "doors" or rods the birds can walk through, but not out. A baited trap would seem more efective, altho the walk in trap could be used in a roost the flock likes and is determiened to use. But could bait help the pigeons ignore things and make them more intent on getting trapped?
Also, once upon a time I heard that exterminators sometimes can use treated or "poisoned" feed that's not really "poisoned" that will kill the pigeons, but by eating that "treated" feed changes the sound of the pigeons and their calls ..... to those sounds similar to crows. Supposedly "drives away" the rest of the pigeon flock as they're
social creatures, while shunning/abandoning/ "austrsizing" to affected bird that ate the bait. Never actually experienced this myself, but maybe a "rumor" worth looking into if extreme solutions are called for?
Try the trap method, esp for total removal.
I have some experience in this regard. Trapping pigeons is easy but time consuming. It is best done with a quail trap.
The procedure is:
Place the trap in an area where pigeons are presently feeding, or on a flat surface near their roost. Tie the door open and place several pounds of corn near the back of the trap.
Pigeons are extremely neophobic. They will not go near the trap or touch the feed for several days. But by the end of the first week you will see some of the corn gone. Within a few more days, you will need to replenish the corn supply daily.
Once the birds have become comfortable feeding inside of the trap, ten days to two weeks, it is time to drop the gate on the baited trap.
When dealing with a flock of 150 birds or more, I would find the trap filled to bursting after 12 hrs set, 30 to 40 birds. I would usually catch about half that many the second day and perhaps 10 more on the third day.
Then it is time to tie the trap open and start the entire process over again.
I suspect that I may have caught a few pigeons multiple times. As I drove home from work with them about twenty miles, and then released them one at a time for practice with the 12 gauge. But I am not the best shot gunner in the world.
Avitrol is the "poison" spoken of. It is registered with the EPA as an alarm agent. But it is definitely a poison and will kill pigeons deader the heck. I have not used Avitrol in about fifteen years, but I once used it regularly.
The really interesting thing about Avitrol is that it is bird specific. I was worried about killing some person's pet if the pet consumed poisoned pigeons. I contacted the manufacturer before using Avitrol for the first time, and they assured me there was no risk of secondary poisoning.
I can attest to the veracity of their statement as I watched a stray momma cat raise a litter of four kittens on Avitrol killed pigeons. That was the fattest, happiest litter of feral cats you ever laid eyes on. They looked like they had free access to the "Little Friskies" warehouse.