Extra mechanized wooden whistles and bellows create the call of a cuckoo bird and a tiny quail. When the clock strikes the hour or half-hour the door opens, a cuckoo appears and calls along with the clock's gong strike.
This clock is hand made in the Black Forest in Germany. The mechanical brass movement is driven by two weights and time escapes with the tick of a traditional pendulum. The cuckoo call sound is made by two wooden whistles with bellows inside the clock case.