When I am asked what the most difficult aspect of raising backyard chickens is, without hesitation, I respond, "Keeping them safe from predators." If you keep chickens long enough, eventually you'll have a run-in with a predator. Learn more about protecting your chickens.
Unfortunately, chickens are very low on the food chain and pretty much everything wants to eat them. No matter where you live, you have to worry about predators. They exist in urban, suburban, and of course rural areas, and are always on the lookout for an easy meal. But realistically, it's not a losing proposition to raise chickens. It's just a matter of being smarter and more vigilant than the predators.
Fortunately, most of the common predators are predominantly nocturnal and hunt mainly under the cover of darkness. It's rare to see a raccoon, opossum, weasel, coyote, fisher cat or wolf out and about during daylight hours, although a hungry or sick animal can become desperate and emerge from hiding. Locking your chickens up in a coop with latches on the doors that even a wily raccoon can't open is your best line of defense against a night attack. Windows and vents should be covered with 1/2" welded wire to prevent even the smallest of weasels from gaining access. (Chicken wire is useless as window covering since a raccoon or other animal can easily chew through it.)
Solar-powered blinking lights installed around the perimeter of the coop can help to keep wild animals at bay, since they believe the red lights are the eyes of another predator. If you can't be home until later in the evening, an automatic coop door is helpful since it shuts as dusk approaches once the chickens have all gone to roost.
While a coop should keep your chickens safe at night, there are still predators that hunt by day. Although dusk and dawn are the preferred hours to hunt for predators such as fox and coyotes, it's not uncommon to see them in broad daylight. Dogs are also a danger to backyard flocks. Snakes and rats will come around looking for eggs or baby chicks to eat.
Chickens are safest when they are kept penned up during the day in a large enclosed run. Run fencing should also be welded wire—1" will usually be sufficient—because chicken wire, as mentioned earlier, won't keep a dog or fox out of the pen. Chain link is effective against larger predator such as bobcat or bear, but will allow access to smaller predators like weasels, snakes and rats and the occasional raccoon who tries to reach through the fencing to grab a chicken.
Run fencing should be sunk into the ground at least 8-12 inches and then angled outward so if a predator tries to dig, they will be thwarted by the fencing. Digging a trench around the run and filling it with rocks or metals scraps can also make digging underneath the fencing to gain access more difficult.
The top of your run or pen should be covered as well. Not only can fox and raccoon climb very well and could easily climb over, there are aerial predators to consider. Hawks, eagles and owls will all make a try for your chickens if given the chance. While owls generally hunt by night, and hawks and eagles tend to be out in greater numbers early in the day, they all can be a threat to your chickens while they are outside.
Simple bird netting or plastic poultry netting will suffice over the top to keep the raptors out and also work to keep any wayward chickens in. Although they technically can't fly, chickens do a pretty good job at getting over low fences. If you aren't worried about your chickens getting out or anything climbing over, simply stringing fishing line across the top of your run in a diamond pattern no more than four feet wide or so will deter most hawks and larger raptors from flying into your chicken pen.
Free ranging your chickens will likely never end well. They are just too vulnerable to predators and there are too many predators to successfully guard against them all. However, you can mitigate your risk though by doing a few things. Supervising your chickens while they are outside is a good idea. If that isn't viable, then having a rooster in your flock will at least serve to give your hens a better chance at being warned and given time to head to safety.
Having a LGD (livestock guard dog) or other guard animal such as a donkey, goose or alpaca will help to keep your flock safe. Limiting your free ranging to only certain times of the day (such as early afternoon) or certain times of the year (summer and winter) when predators seem to be less apt to pay a visit can help also, as can varying your schedule to keep any potential predators on their toes and unable to count on a routine.
Bird migration seasons in the spring and fall seem to carry with them larger numbers of predator attacks, as does the spring when most animals have extra mouths to feed or are out teaching their offspring how to hunt and the fall when food sources start to grow scarce.
Installing a trail cam trained on your coop can help you to determine which predators might be lurking and possibly attempting to gain access, as can looking for paw prints in the snow or mud around your coop and run. Remember to check your state laws before you attempt to trap or kill any predator. Most aerial raptors are protected by federal law and the states have laws governing your rights to shoot or trap various predators, although many states to allow the shooting of any animal that is "running livestock". In most cases, though, learning to live with the predators and keeping your chickens safe day and night ends up being a far more equitable solution.