Almost every time a chick has a noticable comb it's a boy. Girls generally small narrow combs with no color until they are almost ready to lay, about 20 weeks. Here is a picture as an example http://i17.photobucket.com/albums/b83/Kyeaideh/Photos/DSCN1065.jpg Just looking at your pictures you have a few obvious looking boys Pic 1, Little black chick facing the camera (australorp?) Pic 2, Barred rock chick in the bottom left corner. Brown chick all the way on the right standing on the perch. (partridge?) For me I've found that most single comb chicks can be sexed even at birth by comb size, it's easier to see if you have same age same breeds to compare to, fairly accurately.