Ducks are notorious for having very aggressive sex. There are plenty of species which are well documented to have monogamous, long-term sexual relationships. Off the top of my head, seabirds have monogamous sexual behaviors: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Seabird_breeding_behavior" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Seabird_breeding_behavior</a>