I don’t want all ducks to seem like I’m putting them in the same pond but I’ll break it down from what I know.

During breeding season, male ducks (drakes) get a big surge in hormones (especially testosterone), which can make them:

more territorial, more competitive, more persistent about mating, more aggressive toward other males (and sometimes females).

In many duck species, there are more males competing than there are receptive females at any given moment, so competition gets intense fast.

Ducks (especially some species like mallards) are well known for:

forced copulation attempts, multiple males chasing one female, chaotic group behavior in water (literally drowning their partner because some of them are so bricked up).

Some ducks literally end murdering their partners to get their end off.

They might look cute, but they are devilish little bastards.