The term 'Bird in a Clock' is often used to refer to the CUCKOO, a small bird that is known for its distinctive call. The CUCKOO is often associated with clocks, as it is featured in many traditional clock designs. The CUCKOO's call is used to indicate the time, and it is also used as a symbol of time passing. The CUCKOO is a common bird found in many parts of the world, and its call is often heard in the early morning hours.