Oh those hormones, if you'd feel better separating him then by all means do. Drakes are so aggressive when mating some worse than others. and seems first 1-3 yrs they are at their worst. Here mating season is over in the fall. How about your geese do they try and intervene? my geese will pile around the offensive drake and can sometimes run him off, they don't like any hanky panky going on in their yard. If he is injuring them then he dif needs to have some time out.
I wish the geese would intervene! Sometimes they stand around squawking, but mostly they just act like big babies. They're even scared of the tiny disabled chicken that lives in our yard.
Today I put the drake on his own for a few hours, and within five minutes of letting him out he was attacking one of the girls again. He seriously does not stop unless he is napping, it takes up the great majority of his day and the ducks have bald spots on their necks where he holds them down. One of them is very unhappy about it, too. I will feel bad locking him up for the next month, but I have seriously reached my limit of how much abuse I can stand to see him give my girls.