Reverse engineered circuit diagram of a commercial Electronic Bird. This one was built into a plastic christmas ornament and runs off a 9V battery. Note that L1 is actually just an audio transformer with an unused secondary winding.
Here is another commercial circuit of the same type as shown above, but this one operates on 3VDC supplied by two AA cells. It is therefore able to use fewer parts but is not as loud. These ones run off a single AA cell and there are three slightly differ