From the eBay listing:
...one of a kind singing bird box in combination with a cigarette case. This sterling silver case has 4 sides that fold open in and give acces to the cigarettes. In the centre of the case behind glass panels is a Griesbaum singing bird movement. By pushing the stop start knob this lid will jump open and a little bird will appear. It will turn from left to right moving its beak and wings and sing a song with a loud and strong voice After it is finished it will return into the box and the lid will automatically close again. The mechanism is spring wound. The complete case is machine worked in combination with unbelievable highly decorative engravings.
The eBay listing features many more photographs and a video clip of the bird in action. Here's the link for this singing bird music box automaton.