You really need the right breeds/birds, the right rooster or dominant hen, the right place, the right dog, the right perimeter fencing(if in town), the right hide outs/duck and cover places and the right attitude.
Right breeds/birds~birds that are docile, slow moving, overly fat, used to being picked up in the daytime hours and have no quick reactions to alarm calls and aerial danger flying overhead are just sitting ducks for hawks.
Silkies, overfed BOs, Polish (they can't see overhead as well) or any other birds with a slow, friendly, docile manner that are used to shadows overhead(humans) stooping over them and picking them up. All they will do is duck down and freeze, instead of run for cover as they should be doing. You'll want flighty birds that instinctively move away from any and all potential predators..including you.
Breeds that are naturally good at free ranging are most of the heritage lines of birds such as Black Australorps, New Hampshires, Plymouth Rocks of all variations, Rhode Island Reds, Buckeyes, Delawares, Wellies, Doms, Leghorns, etc. These old timey breeds make good free range breeds, even when derived from hatchery sources. There are many breeds out there that still have good foraging and free range tendencies.
Contrary to popular lore and belief, white chicken breeds do not specifically attract aerial predation. Any and all birds I have lost to hawks have been those that were grey with a barred pattern feathers~those birds more close in appearance to the hawk's natural prey. And those birds were ranging and living side by side with many white chickens...I've never lost a white chicken to an aerial predator~I range mostly that color and have done so since the age of 10.
Right age~ The younger you can get them out on free range, the better, particularly if you have older flock members to show them the ropes. Chicks kept in brooders and houses until they are 4 weeks old and older have grown used to sounds and sights in the house and no longer startle as easily, nor are they conditioned to outside sounds and sights. While they are still little chicks they instinctively react to danger signals of shadows overhead, the call of a hawk, fast moving animals, etc. The older, house kept chicks can still learn to adapt but they are 4 wks behind on the learning curve and just the right size for a hawk to snatch and run. I turn out my chicks at 2 wks of age to learn about free ranging with the older flock and am always amazed at how quickly they react to alarm calls and how quickly they find cover. Try an experiment with your new chicks in the brooder...give them an alarm call as if from a rooster and watch them run for cover! They come out of that shell equipped, so make good use of it before they are big enough to attract aerial preds.
**********Don't hatch out chicks in the fall and then try to free range them~this I have found out from personal experience. The leaves are gone from the underbrush and trees, hawks are migrating through and are hungry, and juvenile chicks are the perfect size for hawk predation. Keep the chick hatching and subsequent free ranging to the time when most animals have young on the ground, cover is plentiful, and the hawks are not traveling through but have specific territory and young of their own to protect and feed. This is also the time crows have their young and are way more vigilant than we ever could be...and there's nothing a crow pack hates more than a hawk. They will chase them, pecking them and harassing them until they flee, screaming and going as fast as they can.******
Right rooster or flock master(can be a hen)~ A good rooster will sound the alarm before you even see the threat and will have trained his flock to listen and act on it. He's worth his weight in gold when it comes to free range. Most will not fight a dog or other 4 legged predator, but the rare few will stand off a hawk, challenge a hawk or sacrifice himself for the flock. Mostly they will get the flock to shelter when a pred is in the area. A dominant hen can take over this role if she's the right sort.
Right place~ Areas that have plenty of trees, fence rows, shelters, shrubs, etc. where a bird can run and duck under to avoid the stoop of a hawk. If there is a lack of natural shelters or hides, creating them at convenient distances throughout the range can mean life or death for your chickens. Some use pallets up on blocks, some even use pup tents, trampolines, and tarps over range shelters made from cattle panel hoops.
Right dog~ A dog that lives outdoors all the time, is safe around the birds and sees them as living in his territory, so they are automatically protected from predator threats..even those from the sky. He is watchful all day and night and his constant vigilance lets area preds know this is a risky place for a meal. He doesn't have to cost a lot nor need some high dollar training or have to even be a LGD breed...mine have all been lab mixes that were unwanted by someone else~read FREE~and served years of unfailing, loyal service to the flocks and to the family. Loved companions, good dogs, fierce flock protection and have saved my flocks over and over. I'd never try to even have chickens~be they penned or free range~without a good dog to watch over them when I am gone all day and sleeping at night. They are indispensable to having livestock on your land....and that's just what chickens are.
Right fence~ The right fence can and will slow down most canine preds from doing a quick grab and snatch of your birds and also keep your birds contained. They don't usually fly over a fence, they fly to the top of a fence and drop down on the other side, so removing any surface that makes for good landing at the top of your fence is imperative~even if you have a 6 ft. high fence. You can string light wire there above the hard top of the fence/gait to discourage the hop up or extend the fencing materials above the posts and gates by 6-8 in. Chickens, even adult ones, can regularly roost in trees and barn rafters, so a 6 ft. fence does not mean it is going to stop this behavior. Even clipping wing or wings can sometimes not deter a determined escapee.
If you have a good fence and keep your birds contained and you still get a neighbor's dog breaching those defenses, you have a leg to stand on when it comes to the legal aspects. A good looking, cheap and effective way to protect suburban birds from 4 legged preds is a simple electronet poultry fence on a solar charger...you can move it to different areas, you can put it away and use it another day, it lasts up to 10 years with good care, you can place it around your coop and not worry about coons, foxes, possums, etc at night and it will shock the vinegar out of even a black bear...and it will definitely keep the chickens in if you leave it energized.
Right attitude~ To free range, one has to accept the risk of possible loss. If done correctly, those losses are very few...I've lost 4 to aerial preds in the last 10 years or more. Three of those were just this past fall(2014) due to me hatching chicks in the fall, right when the hawks are migrating...bad mistake, never to be repeated. I've lost 1 bird at night because she roosted in the barn loft where the dogs could not defend her and got picked off by an owl. All of these were barred rock pattern birds, 3 were due to human error and poor judgement and one was due to poor judgement by the pullet, which is an acceptable loss to me. Don't need stupid birds out on range. In other words, she was too dumb to live and so didn't get to do so. All in all, these few losses over many years and many birds free ranged tell me that free ranging can be done with minimal loss if done properly.
Another important attitude to have is that you are going to do everything possible to avoid predation, not just turn out your chickens to the grass with a kiss for luck~ then cry to all and sundry when it goes wrong, telling anyone who free ranges they are putting their birds at risk and are negligent. (This happens more than you could possibly know...people try it once, the wrong way, and then announce it can't be done safely.)
Free ranging can be done and done well for many years if you have the right system in place that insures your birds are just as safe as they are in a coop and run...and many, many stories of predation start right there~in a coop and run~so these are not fail proof places to keep chickens.
There really is no such thing as a Ft. Knox coop unless it is, indeed, in the middle of a Ft. Knox gold vault. A black bear or a determined pack of dogs can show you in about 5 min. how safe your coop and runs really are. Chickens in a coop and run are like fish in a barrel to predators and there is no possible escape there...at least out on free range they have a chance to run, fly, duck and cover and you may not lose all your birds in one devastating attack .
Feel free to ask questions for clarification.