From the eBay listing:
"Domed brass cage on a circular drum base with original gold finish. The bird, with real feathers of yellow and black, on a T-shaped perch, is posed in a bocage of leaves made of fabric complete with the traditional miniature Black Forest red toadstool. The bird's head swivels, its tail flutters up and down and its beak opens and closes in time to the song which is a complex and long sequence of warbles and trills and whistles like a nightingale."
Here is the eBay listing for the Karl Griesbaum Singing Bird Cage Automaton.