While they (and turkeys) may be smart enough (and agile enough) to fly over a six foot fence to get out of the pen they do not seem to be smart enough to fly BACK over the fence to get inside, no matter how desperately they may want to. And of course you may not want to clip their wings in case they still manage to get out so they retain accurate flight as a means to escape danger. Also, no matter what kind of symbiotically friendly relationship you have with them at all other times you may very well be seen as a DANGEROUS entity when you open the gate they have been whining beside all afternoon to get back in. On a positive note, this means you can get some exercise while attempting to corral them to get them locked up before dark. And, to agree with other posters, you can do as much as you can and take all the precautions you can think of only to have them get eaten, commit suicide, or die for no apparent reason no matter how hard you worked to ensure their safety. Despite all this, just enjoy them and be glad you have the opportunity to have them.