how to introduce a new duck to my flock

[Crazy Maizie]

i already put the new ducks in a new cage and put it next to the old ones cage, my top drake wanted to just come out of the cage to attack them and keep bumping into the walls towards them. he stopped after 2 of 3 days now he doesnt try that and its been 14 days i think.
however whenever i let them out together the drake still attacks them and i have to stop them

Separate the aggresive one to see how the rest get along. I know it's been stated many times, but having too many drakes can lead to aggression even if the drake is being aggressive to the female. Its kind of like they need to show off and prove themselves.