A cuckoo clock is among the most unusual type of clock there is. While there are many different types of cuckoo clocks, the vast majority of cuckoo clocks are pendulum clocks that give the time by striking the hour using whistles that often sound exactly like the call of the cuckoo bird. Most cuckoo clocks are made in either the shape of a birdhouse or chalet. Also, most cuckoo clocks now have a small mechanical cuckoo bird pop out of a door on the hour to accompany the chirping noises of the .