This is weird!!

I have 6 kittens/cats and 4 foster kittens. Right now most of them are enjoying the morning fresh air. I have huge living room windows and they are all open(screened in of course). So they love to sit in them..anyway..I hear this weird noise...
It sounds like a bird chirping..but not exactly...its not outside its inside..so i investigate. Its my 8 month old semi-ferral cat (orange and white tabby)
He is behind my couch (he never meows) making this funny noise that sounds like a bird chirping, but a cat faking it. Is he trying to lure birds to the window? It was so funny. I asked Tyler what in the world he was doing, he had this funny look on his face and his tail was wagging. He is a peculiar cat. ..never heard a any of my cats do that before.

My cats would always do that when they would see a bird. I always called it their bird noise. I noticed that my one kitten is starting to find his bird noise. I'm not sure why they do this, but it's common that cats will make this noise when they see birds.

That sounds adorable! My cats love sitting in the windows and watching the birds too. I've got some cute pics of them doing that.

Sometimes Amadeus will make this snorting type noise... but it seems like when he wants to play... I don't know!

I think you're describing what's usually called "chattering." Here's an article that describes all the sounds cats can make:

http://www.messybeast.com/cat_talk.htm

My youngest cat does it too when he wants something that he cant reach (like the laser I point on the wall, a bird, mouse, squirrel, etc)... totally normal. really cute..

Our Annabelle screams, Gracie chirps and Elliott makes a sort of barking noise.
The first time he did it, I thought someone was walking their dog in the ally but it was Elliott "Barking" at the birds.