Next Door Neighbor Is Taking Pictures/videos Of My Backyard Over Fence While Standing On A Ladder. Is This Illegal?

I’m in CO. My insane neighbors, who I share a backyard fence with, have an aggressive Rottweiler that barks all day and night, and other people in the neighborhood have been complaining to them about it. They’ve decided, instead of just properly training their dog, that their dog is poorly behaved because stray cats occasionally cut through both of our backyards late at night. They’ve blamed this on me, because I throw bird feed in my backyard in the mornings (which is completely legal in my county, and I plan to continue to do) and the smell of the birds that come in the mornings are attracting cats at night.

The husband confronted me about all of this at our mailbox once in the beginning, but they refuse to talk to me ever since. Like, they won’t answer their doorbell and they’ll run back inside if I go out and they’re in their backyard. At night, however, I have multiple outdoor cameras, and I can clearly see him and his wife using a stepladder to climb up, lean over the fence, and take multiple pictures (with flash) of my backyard. This has been going on for about three days straight, every single night for ~5 minutes every hour from 6 p.m. to 2 a.m.

I haven’t been confronting them when they do it yet because I wasn’t sure if this “evidence” would be useful or not, and there’s nothing in my backyard that I’m worried about them seeing/reporting.

That’s why I don’t know what they’re trying to find/take pictures of, as there haven’t even been any stray cats coming around at night. All I know is that the obsessiveness & invasion of privacy is really starting to creep me out. I’ve seen that taking pictures within clear view is legal, but is it different when the person is on a ladder and is leaning into your property? Is there any legal action I can take that will make them back off a little bit? I rent my house, but I have no clue what their situation is. Thank you for any & all advice!