The Parrot is a reproduction of a “bird chirp” circuit I found referenced in background research materials for Kelly Heaton’s amazing bird that was one of the Hackaday Circuit Sculpture contest winners.
This circuit is an interesting combination of two LC elements - one modulating the other - around a single transistor.
As always, all notes, schematics and code are in the Little Electronics & Arduino Projects repo on GitHub
Here’s a clip from the workbench, demonstrating some of the sounds that can be produced: