The Nightingale-writings after a poem

From a letter from STC to Wordsworth after writing The Nightingale:

In stale blank verse a subject stale
I send per post my Nightingale;
And like an honest bard, dear Wordsworth,
You'll tell me what you think, my Bird's worth.
My own opinion's briefly this--
His bill he opens not amiss;
And when he has sung a stave or so,
His breast, & some small space below,
So throbs & swells, that you might swear
No vulgar music's working there.
So far, so good; but then, 'od rot him!
There's something falls off at his bottom.
Yet, sure, no wonder it should breed,
That my Bird's Tail's a tail indeed
And makes its own inglorious harmony
Æolio crepitû, non carmine.

(from about.com/classical poetry)