From the Thomas Jefferson Encyclopedia:
The mockingbirds Jefferson purchased in the 1770s came with only a stock of songs from the woods and fields of Charles City County. He must have provided additional musical instruction himself. If he in fact carried a bird to France in 1784, it may have added to its repertoire some sounds common to mockingbirds imported from America. After their month-long transatlantic voyage they interspersed their first European performances with long imitations of the creaking of the ship's timbers.
At least two of the birds in the President's House, however, had already received singing lessons when Jefferson purchased them in 1803 - for ten and fifteen dollars, the usual price of a "singing" mockinbird. Jefferson's butler, Etienne Lemaire, was apparently proud of their serenades, which included popular American, Scottish, and french tunes, as well as imiations of all the birds of the woods.