Critters .... the only effective deterrent (other than a totally electrified fence) I know of is a dog. My SIL has no ‘critter’, deer or crow problems because they have a dog. The previous dog, a Brittany Spaniel, would actually kill possums & skunks he found in the yard. The current dog, a mild-mannered Collie, ‘barks & bounces’ & chases other animals away. Since the dogs were & are not outside in the yard all the time, I think the smell of dog keeps critters away. No such luck with the chicken coop which was away from the yard & inside the wood line ... possums, coons & foxes all raided.
Super aggravating to put in a lot of work on plants, veggies, chickens, etc. & then find them chewed on, damaged or destroyed. :-(
No disagreement with any of that. A few years back we got “adopted” by a stray dog — a shepherd/”something a bit smaller” friendly mutt that was exceptionally well behaved (and particularly great around our sometimes free range chickens). “Lewis” (my daughter named him) didn’t do much chasing, but varmints wisely did not challenge that, and we had no problems with such. The chickens even seemed to understand that Lewis’ presence meant safety* and would tend to congregate somewhat near him.
*Or maybe they sensed that the humans the chickens associated with food also associated with Lewis frequently? Hahahaha!
Unfortunately, Lewis was old and eventually developed hip problems so severe that he’d walk or run around on just his front two feet, hind elevated... We took him to a vet, but hip reconstruction was way out of what we could afford, and would be a temporary solution anyway. We knew we’d have to have him put down soon, but... He did still “get around” on his front legs pretty well, so, we hesitated, and a few days later he just vanished, never to be seen again. Hopefully his “end” was quick. :-(
We’ve had other strays show up since, but all have been aggressive toward the birdies, and my daughter’s 2 cats, so, we had to give those dogs away. Someday if I have more time, we might try to raise and train a puppy...
The one cat will occasionally kill a squirrel - we get such “presents”, or smaller, voles in particular, on the back porch occasionally, but even a half-grown ‘possum? No way. The cat isn’t dumb, and can always come to the back porch for dry cat food after the chickens roost back in their henhouses.
You mention a chicken coop inside a wood/tree line? Yikes! That sounds like just asking for trouble. (Granted, ours are inside widely scattered shade trees, but it’s no wood line.)
Ah, well, if I trap a ‘possum, the chickens get a nice treat!