Roosters do NOT care what breed of ladyfriend they tread. Trust me. They do develop favorites, which they will mount and tread more often than the others.
I have two randy little Sebright roos and a similar bantam Buff Brahma roo which are sneakily trying to mount pullets when the Head Rooster, Carl, is in another part of the yard. They can't get to the young Sebright pullets which are behind a temporary fence while they grow up a bit more. So they sneak up on an experienced large fowl pullet and try their luck there.
Matilda, a Black Australorp, has a body too long for a Sebright to hang on to the back of her neck AND reach the business end. She keeps walking and then eventually flaps and jumps and he falls off. Nobody would dare to try Buffy, she's got that single chick she's raising. All the other pullets and hens hang around with Carl too closely for the Sebrights to snag.
Carl treads as many of the girls as he can in a row as they come out of the coop, every morning. There are 7 of them, and he gets to about four of 'em before they've all scattered. He'll go at it again 3 or 4 times in the afternoon, too.
