Some pen-raised birds make it.  Maybe encounters with wild birds helps.  However, I worry about the long-term impacts of the mixture of pen-raised DNA with wild.  "Wild" mallards on the east coast are virtually all hybrids of wild and surviving pen-raised.  The genes of these surviving pen-raised mallards are producing observable changes in wild populations that might be impacting survival.  I don't think this has been studied much in pheasants, but there are sure a lot of them released.