Yes very much so. I read a marvellous book by Desmond Morris about cats and their behaviour.
Cats use their tails as sign of contement as well as a warning to back off. (unlike my old boy, who when cheesed off by other 2, wont warn with tail, he just strikes out.)
Here is 1 of many links i found for you.
Dogs do the same, so when a dog is wagging its tails, does not mean its happy, they have several way of wagging their tails, but not as much as cat does, E.G. whn a dogs tail is rigid and wagging, it does not mean its happy, its being cautious when either meeting another dog/human etc.

http://www.geocities.com/catwhiskasplace/tails.html

My oldest boy with my love bird chick.