An interesting bird ... does this apply to any of you here?
While many Dunnocks adopt a monogamous relationship with a would-be partner, others engage in more complicated arrangements. It is quite common for one female to engage in a relationship with two males (something that is given the rather grand title of 'polyandry'). Somewhat less commonly, a single male may establish bonds with two or more females (known as 'polygyny') and there are even cases of groups of two or three males consorting with three or four females ('polygynandry')!
http://www.birdguides.com/webzine/article.asp?a=1047