This is probably because, before brood parasitism appeared, responding would have likely had no adaptive value.

这可能是因为，在巢寄生现象出现之前，反应可能没有适应性价值。

Most birds build nests, but several different families of birds evolved what is called brood parasitism, where females lay eggs in another individual's nest.

大多数鸟类筑巢，但几个不同的鸟类科进化出所谓的育雏寄生，雌性在另一个单独的巢中下蛋。

Whichever way you swing it, brood parasitism is yet another example of the fascinating turns evolution has taken.

无论你如何摆弄它，育雏寄生都是进化所发生的令人着迷的转变的又一个例子。

But in the most egregious cases of brood parasitism, why don't host parents take a stand?

但在最恶劣的寄生虫案例中，为什么寄宿父母不表态呢？

This is but one example of brood parasitism, an evolutionary strategy in which one animal tricks another into rearing its young.

这只是育雏寄生的一个例子，这是一种进化策略，其中一种动物欺骗另一种动物抚养它的幼崽。

This seems to partially be a result of how long brood parasitism has been in their environment, and thus how much time they've had to evolve suitable adaptations.

这似乎部分是由于寄生在它们的环境中的时间有多长，因此它们必须花多少时间来进化出合适的适应性。