I haven't lost a chicken to a predator either, I have had chickens for 7 years and they do free range when I am not home. There are predators in the area and the rooster does his job well.we did the tractor because we got it free from a friend...and I thought I was going to let them prep my garden beds, but then we let them go, and they just looked all cooped up (Ha!) when they DO stay there all day for some rare reason. So I’m not attached to the tractor idea but a permanent solution seems like it would have a large start up cost and I’m not sure about the cleaning/stink factor and predator proofing or anything like that...so far we have not lost one even though they free range. One time we came home late, a chicken was not in the tractor. We thought we had lost her, but she was there the next day! So does that mean I don’t have to worry about predators generally?? I‘m just new at this and don’t really know much about it...
Even though you haven't had a predator problem yet, that doesn't mean you shouldn't prepare for it.