I keep a lot of pigeons, and in general I don't let them fly free (no open loft). The comments about only flying your birds while you are supervising and then calling them in, varying times and days, all work. Never just leave your loft open all the time or you will become the local hawk fast food takeout place.
This next does not help much with pigeons, who are up flying and on top of coop roofs, but it will help a lot to protect birds on the ground like bantams. I put eye screws up on the tree trunks around my coops, and on my fence posts and buildings, then string cords, and suspend pieces of light black plastic netting used to protect cherries and other fruit from small birds. I'm not covering the entire area at all, just scattered around over my chicken pasture especially over the bantam area. The cords and nets interfere with the hawks getting a straight run at the poultry, the poultry have more warning and more time to run for cover. There are multiple entrances to my coops and runs that are all open when the poultry are out, so they have lots of places to run for shelter.
I have Cooper's Hawks (bird hunting specialists!) and I have not yet lost a bantam, although more than once I've seen a frustrated hawk sitting on the ground in my pasture while all the chickens have run into the coop or another shelter. In wide open areas of pasture I have also parked things like wheelbarrows, and propped long fallen branches and the occasional surplus 1 by 3 board on them, with big spaces in between. This gives the chickens more places to dash for shelter, and although the hawks could fit in there, they aren't going to walk or hop after their prey. Once they've missed the dive, they go back up in a tree to look for another chance.
The netting is black and not real visible. I have used white cords so the hawks can see and be deterred by the visual barrier. If your area or neighbors are such that you don't want the "unsightliness", you can use crisscrossing monofilament fish line, which is pretty hard to see. If a hawk hits it, he bounces off, strike deflected. You do have to keep an eye on this so you don't get broken pieces on the ground where your poultry might eat it--very bad thing. Best Wishes!
P.S. Not good to even talk about killing/shooting/harassing protected species on the internet, there are people who look for statements like that to report, and even if was just talk you might find a local game warden or federal employee knocking at your door.