Bonjour Francoise,  The Journal of the Musical Box Society of Great
Britain, "The Music Box", Vol. 19 No. 2 Summer 1999, page 41-43, has
an article "Simple Automaton Mechanisms" by Mr. A.J.L. Wright.

Mr. Alan Pratt, the editor of the Music Box, said that the Journal
"provides the would-be constructor of an automaton with just about
everything you need to know about the making of a singing bird.
It is not often that we get the chance to publish such detailed
drawings and description of this, or any other type, of mechanical
music."

The article shows exploded view of the mechanism of a singing bird in
cage, shapes of cam wheels and the diagram of the bellows.  The price
of the magazine is UK pounds 6.00-.

Back numbers of the Journal are obtainable from:

  Mr. Roy Ison
  5 East Bight,
  Lincoln, LN2 1QH,
  United Kingdom

Good luck!

Kazuo Murakami from Japan