Will a rooster be picky about who to mate with?

[Chicky-bock-bock-mamma]

I have a Black Copper Marans rooster who is about 8 months old. He seems to only take a liking to my Welsummer hen, and by that I mean she is the only one allowed to be all up in his personal bubble 24/7. The flock follows him but he seems to ignore the rest of the ladies. I am trying to get some fertile eggs but I don't know if he is giving his "time" to his other ladies.

 

[Egghead_Jr]

I'm sure the other eggs are fertile. Crack a few open and check.