Before anyone contemplates building a singing bird mechanism they
should read Geoff Mayson's book, "Mechanical Singing-Bird Tabatieres",
published by Robert Hale, London, 2000, ISBN 0-7090-6303-2.  This
excellent book shows, in great detail and with fantastic colour photos,
the inner workings of the vast majority of different manufacturers of
singing birds.  It also has a very comprehensive section on restoration.

John Hutchinson's question is answered by reference to Figures 11.6,
11.7 and 11.12.  These show the relationship between the whistle, valves,
mounting plate and operating wires.  As with a conventional organ pipe
chest, the operating wire (push rod) comes through the top board directly
above the pallet valve to ensure there is no leakage when the valve is
closed.  Any leakage around the wire when it is holding the pallet open
is negligible due to the very small diameter of the wire.

Good luck to John.

Nicholas Simons, GB