I noticed today that when my kitty is looking at the birds chirping outside the window, she meows in quiet a weiiird manner. As in its a vibrating meow, where her whole mouth is shaking. I really dont know how to describe it I guess you just have to see her doing it, but whenever she is observing the birds this weird thing happens. More than the sound its the way she does...its just WEIRD!!! Is this common? What is it? I