Mz. Predator Paranoid here.
Basically every predator, including some snakes, like chicken meat. Plug up all holes between fencing, walls, etc. Some predators can squeeze thru holes as small as 1". Snakes can come in and eat eggs through one inch chicken wire.
Lock up your birds at night in a secure coop or run.
Chicken wire keeps chickens in, but doesn't keep predators out. Put welded wire over your chicken wire if your birds will be in a run that a dog or coyote has access to. Raccoons can tear through chicken wire also. If your birds sleep in a secure run, place hardware cloth next to the roosts and around the bottom so raccoons can't reach in and pull your bird thru the wire piece by piece.
To prevent digging under your welded wire enforced run or into your coop, attach welded wire "aprons" to the outside and fold them outward so that any predators wil be digging into wire at the base of your run or coop. (If you need a picture, let me know.)
If your birds are locked in a coop at night, but in a run during the day, put chicken wire or netting over the top to keep out raptors.
Secure all gates, doors and windows with locks that cannot be manipulated by varmints. Raccoons can easily use a slide bolt, twist lock, etc. (I have padlocks with keys on mine.)
If you intend to let your birds free roam, expect to lose a few (or more).
Did I leave anything out ?