I Want Solid Proof

We live in a very quiet and safe neighborhood but even then I've always wanted to install surveillance cameras especially in our backyard. My neighbor has several chickens that he just allows to loiter around and they always end up in my backyard. I suspect that they're the ones raking out the dried leaves in the woods towards the yard which really makes me mad. It's hard work to rake all the dried leaves and wheeled them to the woods only to find them in the yard again. I already saw the chickens once or twice before making all the mess, but I just wanted proof if ever I may have to complain later. I don't want to make enemies, but some people need to be responsible pet owner or chicken raisers.