I think most of my cats have chattered at birds, etc. My male now is the loudest I've seen. He loves to watch birds or sqirrels and chatters his teeth at them. If I go to the window and make the chattering/clicking noise, he's THERE and looking for the prey, chattering along with me.
I read in a cat behavior book that it's the "death bite" a cat WANTS to make, but is frustrated since he can't get the prey. And I was always told the cats were "talking" to the birds and trying to call them down. The death bite theory makes more sense to me, but all I DO know is that my cat means there is something he wants to kill out there.
