monogamous

So birds are monogamous but they cheat as well, within limits.

所以鸟类是一夫一妻制，但它们也背叛，有限度地。

Unlike most other fish, they are monogamous and mate for life.

不像其他的鱼类，它们是一夫一妻制并终生厮守。

Many birds are socially monogamous, which is to say that the male and female form an exclusive bond and spend a great deal of their time together.

许多种鸟类都实行社会化的一夫一妻制：雄性与雌性组成独占性的结合，一起度过生命中的大部分时间。