I think there's little doubt that serinettes were indeed used to
teach song birds to sing, as demonstrated by a superb automaton,
'La leçon de chant', to be found in the Gelis collection at the
Musee Paul Dupuy, Toulouse.
Made by Robert-Houdin and dating from 1844, it was acquired by
Gelis from the widow of Robert-Houdin's son which may explain why
it is in such good condition. Being at the museum a couple of
years ago, I made a video of sorts which can be seen here:
Mark Singleton's 'Colibri' may well be unique, although about
thirty years ago I restored something similar but which was larger
and rather more conventional. It had an automaton bird but no
'sifflets' and with a mandoline arrangement, the combs having the
normal range of tuning with no pretence at imitating birdsong,
although there were quite a few trills I seem to remember. One
tune which it played was of course 'The mocking bird'.
One suspects the 'Colibri' was a special order from Dawkins/Rivenc,
who did make some strange things. I have seen at least two of their
music boxes which had the comb and cylinder accompanied solely by
a very large drum / tambourine centred behind the movement.