At first, they tried, in a panic, to get back in with their sisters. But the sisters decided that freedom looked like fun, and quickly, five more flew over the fence. While I stood there with, I am sure, my mouth hanging open in shock, the first seven explored the woods. The other two remaining chickens wanted freedom too, and, as I admitted defeat, I let down part of the fence so they could get out and the others could get back in.
There is nothing I can do to catch them in the daylight, and as this happened at 7:30 AM, they have a long day of free-ranging ahead. They will probably return to the pen because it is, after all, where their food and water is located. In the meantime, I imagine my plants will have chicken-pecked holes in them again, and my patio will be covered with chicken poo. I believe a wing-trimming is in the works.