I emphasize with your frustrations over the visiting chickens. I am getting my chickens under control, but it is expensive because I need to provide a large enough enclosed yard. I have free ranged my chickens since moving to the country, (no HOA or laws against ownership to deal with) and my closest neighbor is about a 1/4 mile from my house. I don't believe they go that far, she has never said anything. My immediate neighbors East and West are the one's land being visited by the girls and neither neighbor lives on the land. I tried electric wire to keep the chicken murdering dogs out of my yard and
it is working. Unfortunately the girls just scoot under the lowest wire and feast on his wooded land. I so hoped they would be discouraged.
I acknowledge I still need to enclose my chickens. So, I have the plans made for the "aviary" because that is what it will be. It will cost me nearly $1 per sq ft to raise the existing fence and put a shade cloth roof on the yard. Last year had a chain link fence put up to enclose their yard rather than electro-net fencing. Once I get a contractor and the supplies, I will be able to keep the girls comfortable even if they are still enclosed. The covered yard allows each bird 100 sq ft per bird based on a flock of 24 hens and 2 roosters. I will still be able to let out to free range part of the day, since I am home and work outside many afternoons.
I think you still have some options before you visit the realtor. First, based on my experiences in TX, livestock owners are responsible for their animals, and for keeping them from damaging their neighbors animals/property. Some issues are harder to deal with, such as dogs and chickens. Anyway it may be worth visiting a lawyer for a clear understanding of your rights as a property owner, what you may do to protect your property's value and how to seek recompense for damages. I think that once your neighbor realizes how much it will cost him to continue to free range the chickens and not restricting them to his property, he may decide to take the necessary steps to keep them home. Once you know what you can could do, I would then write a letter for the neighbor, since polite conversation proved fruitless. I would outline the issue (have photographs showing damage), steps taken up to this point to resolve the issue and what you will do if the chickens continue to damage your property. Send the letter certified mail, receipt requested and keep it as a foundation of your plan of action. I would approach the issue financially as that could prove the most effective. For example, if he continues to fail to contain his chickens you can present him with
bills from the pressure cleaning company that has to come weekly to remove the poop from your patio and drive, the cost to replace plants dug out and/or eaten from the landscaping, damage to any fruit or vegetable plantings or lawns and any damage to your automobiles paint finishes. We keep our car inside the garage to prevent mice from chewing on the wires, so the girls don't get to sit on the car. Other options would be to get a dog, though unless you
like dogs that wouldn't be responsible, and you would have to keep the dog fully restricted within your property boundaries. My experience with dogs is they will chase chickens treating them as squeak toys until the bird dies from shock. We tried a dog and had to return it. You could also catch the chickens based on the assumption the birds are being 'abandoned', and become a chicken owner of a few hens in an nice coop and run, or if there is a "soup kitchen" that could use them that would be a remote option. It is my opinion, that your neighbor has become the victim of chicken math; thus has far more birds than he did originally. Thus to return the birds to a coop and pen will be expensive, and he is trying to avoid the expense. No one who gets chickens plan on spending "big" money, just a few birds and some fresh eggs.
I never planned on spending $5000 to have chickens. but over the last 3+ years it started with replacing the flimsy, too small coops with a sturdy small steel building ($1200), then the following year, having their yard fenced in with chain link fencing ($1200 ), this winter we surrounded the house site of our land with electric wire to keep out the many neighboring dogs that wander freely in our community($600) and now to convert the fenced chicken yard into 6ft sided, fully covered run with shade cloth ($2500) to keep the girls home. They need that desperately before the hot weather hits so that they can find cool shelter somewhere other than my large shady porches (I can emphasize your feelings about poop on the porch). I wanted to do it, but not quite as soon as I need to do it so I can keep the girls home. Now ya'll may be questioning my sanity on spending so much $$$ on my birds, but once I had the girls for more than 4 years I wanted to keep them safe, and allow them to forage and live their lives naturally and decided it was time to invest in hard scape. So I guess that is what I need to do if I want to keep my girls laying the yummy free range eggs (the eggs from free ranged, GMO free chickens are really delicious. I sell them as fast as the girls lay them) I think the biggest benefit will be the reduction in the loss of the chickens to predators, I replace at least half my flock every year. Now to get your neighbor to feel the same way.