well it depends, if they're wings aren't that large you should be fine, if they are fatter older birds then you should be fine, if they have a big enough place they shouldn't like fly away, muscovies have a homing range and as long as they know where the food is they should stay in the general area, now if they are a lean male with wings that are big enough, like to where the wingtips make an X at the end of them then they can fly. can i see some pics?