LOL LOL the cat chatter sounds so funny! Mine do it at just about anything that moves. Birds, bugs, other cats......whatever is outside that they can't get at!
We have little exterminators too! It's like a game of fun for them, as they pounce on the moving bugs/spiders and play with them to death. Back in Indiana, they never had a problem after eating the bugs...YUK! I would find legs of dismembered unfortunate bugs that met up with the force of Marius's big mouth!
But here in CA, I don't like it when he eats the bugs, because most of them make him puke. Weird, huh??!! So, now I have to watch carefully when he starts going after stuff (and it's not a red laser beam), because I don't want him eating anything weird.