Have you noticed that when your cats discover a bird or a small rodent like animal through the windows, they start clicking their mouth, making a strange stuttering sound as their jaws vibrate in a frantic manner? This could also happen, when you are playing a laser pointer with your cat.
This behavior is an exaggerated reaction by cats to show that they have spotted prey and are ready to bite.
Cats are hunters by nature:
Once a cat locates his prey, he will start prowling from behind the prey, quietly making its way to the target. Once it gets close enough, the cat will pounce on the prey with its strong front claws in a fast, lightening-like motion, giving the prey no chance to escape, then it comes the killer bite which strikes right into the nape of the neck. Cat's canine teeth is designed to lock the prey in the mouth then snap it with its jaws.
Using a rapid juddering movement of the jaws, it slips them between the vertebrae to sever the spinal cord, thus incapacitating the prey...The killing-bite!
Studies have shown that it is this unusual jaw movement that brings about almost instantaneous death, as it is vital for the cat to reduce any risk of injury to itself . So unable to control itself at the site of a tasty bird outside, the cat will sometimes involuntarily enact this special jaw movement.