English: Male mallard ducks, Nature reserve Moenchbruch, Hesse, Germany.
At the photo location, there was a group of four male Mallards loosely hanging around together and this male couple. While the ducks in the loose group kept some distance among each other and occasionally separated, the couple shown on this photo behaved like a heterosexual Mallard duck couple in a way that they always kept very close together and remained separated from the other group. When they moved, one duck of the couple was always very closely following the other one and when they didn't move they frequently established body contact as shown on the set of photos above and below.