Many cats "chirp," creating a chattering sort of sound, especially when watching birds or squirrels outside their windows. Behaviourists believe that these sounds are driven by cats’ unquenchable hunting drive. The sound is generated through the contraction of jaws and teeth and may be accompanied by a small meow. Experts are not precisely sure of the function of the chirping sound, but some theorize that it is meant to reassure prey whilst preparing for a killing bite. Others think that the cat is expressing frustration at being unable to catch that tempting songbird. Remember that your sweet housecat is in actuality a hunting machine; be sure to have a rotation of toys to help satisfy the need to hunt.