Thank you for your interest in keeping pigeons.
We don't suggest leaving birds outside unattended, as that is an open invitation for predators. Never leave any doors or windows open for access from the outside world.
We recommend using 1/4 inch hardware cloths on all and any openings to the coop. Any opening larger then 1/4 inch and predators can gain access easily. You never know what kind of predators pigeon keeping can attract, till you get them, and I have seen all kinds, from snakes to rats, raccoons, cats dogs, even mice.
The loft should be well ventilated yet keep out any drafts of air, wind and rain. It should be weather as well as, predator proofed. You can use a safe trap for birds to gain access to the coop that is safe from predators.
If you have a good size clearing the birds will do well, but any area with lots of trees can be homes for hawks and such birds of prey.