We took on 8 drake ducklings two and a half years ago. We wanted to use them for herding practice for the dogs and thought that it would be better not to worry about eggs - also drakes were easily available since anyone in her right mind would prefer females :)
Life was great until the next spring when testosterone hit and fighting began. We had to isolate one, rehab him, and then eventually split the flock into 2 groups. This spring we had some more scuffles, and had to isolate one more, do some rehab, found him a buddy from the other group, and then reintegrate so we were back at 2 groups.
Fast forward to now. Some rainy weather, ducks inside their coop longer than they should have been and all hell breaks loose. I hear thumping and when I open the door out crawl the wounded. One totally beat up, two bloodied and two untouched.
Beat up boy gets put into isolation. Group of three banish one of the untouched, so I thought maybe he was a pacifist and put him in with beat up boy. Beat up boy drags himself across the yard to fight handsome boy. Sigh. I put handsome boy back in with the other three and he just keeps his distance but remains untouched. The other three have most of their feathers and I am not sure if it is their blood or beat-up boy's.
Fights seem to come and. It isn't always the same drake, and they do heal nicely, but really. I am sick of the posturing and fighting. On the other hand, we can't add females with this many males, and unless we want to eat them they are here to stay.
So, when people ask about keeping just drakes - I would say sure as long as you have the space and coops to separate them out during high testosterone periods or whenever the weather sets them off.