But they do not (as, for example, lice do) live on their hosts continually. Once a bird fledges, therefore, it leaves its parasites behind.

但是它们不会一直寄生在它们的宿主身上(虱子才会)，当鸟儿羽翼丰满时，鸡蚤就会离开。

youdao

Is the first bird or egg, you do not know, I do not know, only the birds know.

是先有鸟还是先有蛋，你不知道，我不知道，只有鸟知道。

youdao

I hope you will become like that little bird, and dare to do things other birds won't do.

我希望你也象那只鸟一样，敢做其它鸟不敢做的事。

youdao

Last time I checked, bird-watching didn't do much to improve one's fitness.

FORBES: The Incredibly Uneven Recovery

Now that translates rather amusingly, Richard III is rhyming slang for bird, bird is prison slang for length of sentence - what it means is don't do your sentence twice over.

BBC: Breakfast with Frost