why did the wistle in out the mouth when see the gays girl,s?

Answer 1

It's a universal expression of appreciation and interest by guys. Most girls don't seem to particularly like it (at least publicly), although everyone likes to be appreciated and admired. I guess it depends who does the admiring, and how they do it.

Answer 2

It is a non word way of saying "You are gorgeous, Doll!" all in one brief sound. Most women are embarrassed on the outside, but on the inside, they are say, "Well, that felt very flattering."