Now let us suppose that the ancient progenitor of our European cuckoo had the habits of the American cuckoo, and that she occasionally laid an egg in another bird's nest.

现在让我们假设我们欧洲杜鹃的远古祖先具有美洲杜鹃的习性， 并且她偶尔会在另一个鸟巢中产卵。