I won't worry as much about keeping your chickens in as I would keeping, dogs, cats, hawks and kids out. Chickens won't leave if they have a good gig going on. But EVERYTHING else will be trying to get in!
Go at least as high as you are willing to stoop and cover with chicken wire.
I watched two of my barred rocks (21 week old) fly about 8-10 feet through the air and almost over a section of 8 foot high fence I have. I was quite surprised! Most of my fence is 4 foot and if they are content they stay put. But if something startles them I know they can get over the 4 foot fence, which isn't so bad as they may be able to flee from danger.
So, I would say to be sure at least 8 feet or cover their area with netting.
It really depends on the size and age of the chicken. The smaller and lighter the chicken, the easier it is for them to fly. I have all DP chickens and they get out of their 6' pen all the time (I know I am bad, no netting over the run) They don't fly from the ground to over the fence but use the exterior nest box as a "stepping stone" to get out. I really don't mind them getting out much since they can't get to my patio but I do worry about predators getting them.
How high CAN they fly and how high WILL they fly are two separate issues. Heavier breeds, once grown (because young pullets are lighter and fly better), can generally be contained within a 4 ft. fence. Lighter breeds can go quite a bit higher. Many say that with wire fence with no visible top or ledge appears to be much higher to a chicken, because they can't really judge how tall it actually is - there's no "goal" to fly to (or over). All of our fence is 4 ft, and none of my chicken have ever flown over it. Now, my EE flew on top of our (covered) run with no problem, and it's 6 ft. high. But she was trying to get away from a harrassing rooster. She never flew over our 4 ft. fence. Basically, as long as there is plenty on their side of the fence to keep them happy, they usually will stay there. You can also clip wing feathers to help, if they end thinking the grass is greener on the other side....
Yeah I have to agree with the others, depends on the size and age of the birds. I've had hens and a rooster that could jump what seemed like 7-8 feet almost straight up just so they could roost in a tree. One rooster a friend and I caught could fly level about 4 feet off the ground for almost 100 feet.
I'm wondering though if clipping their wings could be an option for you, might through them off balance when they take to the air to possibly hurtle a fence.
Yeah, agree with the rest. The only chickens I have that are relatively easy to keep in are the bantam cochins. I've seen my BC fly up to 3 ft...I'm sure they could go higher if they wanted, but they don't.
Thanks all. We have a pretty big yard but the area where we dine al fresco and BBQ I'd like them not to frequent. Sounds like if I put up a 4 foot fence that they should, for the most part, stay out of the fenced area. Appreciate all the responses!
I think it depends on your chickens. I have a flock of 13, and a six foot fence contains all but six. These six fly out religiously. We cannot put a top on the run because of the trees in there. One of barred rocks and rhode island reds occasionally roost in the tree. The lowest branch is ten foot high. I've tried using fishing line around the edges of the run to keep them in, but it didn't work. I garden, so I have to find a solution soon.