I lean towards what new chick said too. Obviously you don't want to start a war with someone who has adjacent property, but then you might have a lot more to endure. I think people really do need to have some consequences for their actions or they just keep them up and/or escalate.
I completely understand your celebration of the wildlife you were privileged to see and the sadness at being powerless to stop the changes around you. It wasn't a stupid post! Have you talked to your other neighbors, the ones who were horrified along with you? Perhaps you could all approach him. Or all let the authorities know.
We have lots of predators too, but even if one managed to get a chicken I wouldn't want to kill it. Every time I see satellite pictures I'm shocked at how little land the animals have left. I root for our fox every year and love seeing the hawks. I just also make sure my chickens are very secure.
So sorry you're stuck in this situation.
First let me say thank you all for your responses... I've pulled myself together... had to go to work yesterday afternoon... life goes on. My neighbors and I have all discussed calling the wetland commission on this guy... but he actually is good natured and no one wants to put a negative spin on our little idyllic spot here... so we all just put up with him. He did move my chicken coop for me with his tractor. He is always the first out with a chain saw to clear the road if a tree falls. He seems quite conservative and I wonder how he justifies blatantly breaking the law which he has done twice now. He hunts, has a web camp on his property... is very knowledgeable about wildlife and yet seems very ignorant when it comes to the effects of his actions on the balance of nature. Unfortunately, the way our properties are situated everything he does is sort of right in my face. I'm up on a hill looking down on him and can see everything he does. It amuses me that after he clear cut the whole property he did manage to leave one shrub next to a tree... a barberry... which some of you may know is a nasty invasive weed and if you were to leave one shrub, why that one.
Red tails supposedly mate for life so I guess I will see what happens next... does the remaining bird stay ? Without a mate and young to feed it has become less aggressive... if it chooses to hang out but continues to attack the pigeons then its fate is certainly sealed... but it may just be content with small stuff now that it has no young to rear. I do not begrudge any of the losses I have had due to predation... with each new threat I have just added electric fencing or whatever is needed to protect my own... at this point my flock can only free range when I'm out and about in the yard. Half the fun for me is just seeing them out and about doing what chickens do.