Roosters are a must, as they keep watch and will sound the alert to something coming overhead. My rooster used to alert when the motorized hang gliders would go over our land. If they see a shadow pass overhead, they notify everyone to duck and run!
You can also make your land unfriendly to other flying birds by hanging long streamers of the bird repellent mylar ribbon, those reflective 'eye' thingies, pinwheels, or anything else the moves and blows in the wind. I've 3 of those big plastic owls impaled on fiberglass garden stakes that [so far] have kept the crows and hawks out of the yard. Before the owls were in place a hawk got one of my Silkies, 3 feet from my door, so it wasn't the least concerned with coming in close to the house.
The coyotes are going to be your biggest problem as they have little fear, and are crazy persistent. They will come anytime during the day or night too. We've got folks in town who can't let their kids out to play as the coyotes are sleeping in their bushes during the day, and growl at them if they try to throw rocks to spook them away.
Try one or two of those cool motion sensor sprinkler heads. If water came on randomly and sprayed them it might be enough to spook them to stay back. Add lot of windchimes too, perhaps sound may work too.
A university site about coyotes said that Vick's Vaporub saturated strips of rags tied down low at nose height on shrubs or stakes would be an objectionable smell. Gotta love Vick's!
I attach large goat/cow bells to the latches of my chicken coop so if the raccoons try to get in at night I can flip on some lights to scare them off.
Rather than a heavy movable tractor, which honestly, is going to get old real fast, consider building one centrally located coop that is convenient for you, secure from predators, with a fenced outdoor run for vacations and rainy days. If the chickens become a lot of work, you aren't going to enjoy them. Remember, that just because you have the stomach flu, migraines, or threw your back out, someone will still have to go out to let them out, feed and water them, so do you really want to haul a tractor around your property too?
LOL, I know, I'm a buzz kill! Seriously consider that oramge perforated plastic fencing stuff that is temporary around building sites for erosion control. You can easily drive some fiberglass garden stakes in the ground and unroll it around the stakes so they have a large yard. Leave that in place until the greenery looks well mowed, then unroll the temporary fencing to enclose the next adjacent block of space and repeat. If you do it this way every other week or so, they won't eat down all the plants to bare dirt and then things will recover in time to cycle back to that area again. It also will train them to stay relatively close to their coop. The farther they wander, the more at risk they will be in your predator rich neighborhood.
