THE NIGHTINGALE:  DT entry. No tune given or source specified. There is a midi linked to, though, and in spite of doubts expressed (and no indication being given as to where it came from) it is the right tune; or at least the tune most commonly heard nowadays. Noted by Baring-Gould in Cornwall, where, according to him, it was the usual tune: date(s) unspecified but end of 19th/ beginning of 20th century. He considered the tune to be of the second half of the 18th century. He further pointed out that the words were written by Isaac Bickerstaff for the opera ("dramatic pastoral") Thomas and Sally, or the Soldier's Return (Covent Garden, 1760) with music by Thomas Arne; and that Bell's guess at a date was way out. Arne's tune seems not to have made it into tradition. Baring-Gould published the tune, with words from Bell, in Songs of the West, English Folk-Songs for Schools, and so on.

All the subsidiary links in the DT file are to other, unrelated Nightingale songs; mostly versions of The Grenadier and the Lady (and many other titles). This brief earlier discussion does relate to it, though:

To hear the birds whistle and sing...lyr