Bird calls are the vocalizations of birds that are used to communicate with one another. The term 'bird call' can refer to a variety of sounds, including the COO (3 letters) which is a low-pitched sound made by doves and pigeons, the TRILL (5 letters) which is a series of notes repeated rapidly, the CHIRP (5 letters) which is a short, high-pitched sound, the SONG (4 letters) which is a longer, more complex vocalization, the TWEET (5 letters) which is a short, high-pitched sound, and the CAW (3 letters) which is a loud, harsh sound. Finally, the NOTE (4 letters) is a single, distinct sound. All of these sounds are used by birds to communicate with one another and are collectively referred to as bird calls.