They should have 5 I've read, though I have 9 ducks and 4 drakes in my flock and don't have too many problems. BUT they are all free range so they have plenty of room to stay out of each other's way. It's really cute how they pick 'mates'....everyone says ducks don't do that but they do. I have a pekin that has 2 pekin ladies, a runner that has 2 pekin ladies, and a rouen and another pekin that have 3 rouen ladies, 1 pekin lady, and 1 runner lady. If any of the other drakes go after a girl that's not 'his' she will fluff up and make all sorts of racket until her boy comes to rescue her