Many, many bird species are spreading bacteria from one place to another, from one rodent to another, by carrying fleas,

As the forest went, so went the bird. It's an indicator species, representative of what we did to the forests. Having it return is perhaps a sign that the forests and habitat are coming back as well.

So, naturalists observe, a flea Has smaller fleas that on him prey; And these have smaller still to bite 'em, And so proceed ad infinitum. Thus every poet in his kind Is bit by him that comes behind.

Panurge had a flea in his ear. [Fr., Panurge auoyt la pulee en l' oreille.]

Then mimick'd my voice with satyrical sneer, And sent me away with a Flea in my ear.

I do honour the very flea of his dog.