judging from my past experiences with pet parakeets and parrots, I would say Yes, for awhile anyway. Chickens are not as much of flyers as parakeets and parrots but I've seen parrots and parakeets flying around jsut a couple weeks after getting their wings clipped. They just have to build up more strength and they can't fly as far but they could still fly. Now as I mentioned they are better flyers than chickens so you may not have a problem with your fence. here's a thought, try to figure out a way to build an inward facing lip of fencing or mesh from the top of your fence. Think baseball backstop, the way the top portion of the fence leans in toward the homeplate. I'm thinking that your birds will try to "hop" the fence more than fly over it, so if there is an inward angled lip they will start at the fence and hop up only to hit the lip which stops them. This lip would not need to be as secure as the lower fencing you could probably get away with bird netting on some poles.
