Avian sound is a term used to describe the vocalizations of birds. The two crossword solutions for this term are 'BIRDCALL' and 'COO'. BIRDCALL is an 8 letter word that refers to the loud, often complex calls made by birds to communicate with each other. COO is a 3 letter word that refers to the soft, low-pitched sounds made by some birds, such as doves and pigeons, as part of courtship or to express contentment.