Ok i imported some brahams and cochins.
Whoa, sounds expensive! Where are you located?
They arrived in early November 2014 and were about 6.5 to 7 months old. Now Cochins started breeding after a months time and i got few chicks. Brahmas on the other hand started laying later. So far all of there eggs till now are not fertile. i investigated the problem a bit and found out that one of the hen has some feathers removed from her back meaning the rooster is supposedly doing his job.
Feather removal isn't part of the job. Sometimes dominant hens remove feathers from subordinates as they pass them, sometimes you'll get an obsessive feather picker that regularly removes feathers from a chosen victim. So I wouldn't consider it a likely sign of the male mating with that hen, myself, but that does depend on your rooster, if he's rough with the hens it may be the case that he is regularly ripping at her feathers, in which case it may indeed be a sign she is his favorite. Or maybe she's just the one that dislikes him the most and therefore tries to pull away rather than mate when he tries to initiate it. In my experience if the hens do not like the rooster there's a very good reason why and he shouldn't be bred.
A clumsy male also tends to defeather females but damaging feathering is not actually a natural part of mating at all. Still, it's accepted as 'normal' by many, as are extremely abusive roosters. So it is normal because many don't cull against it. My males don't ruin my hens' feathering though.
Ok one thing i did not mentioned before is that the male is quite large in size and females are not behind either. You can say that they are giant size. Ok yesterday evening i went to the coop to collect eggs, when i saw something which i wanted to share with you and seek guidance from any experienced member who might have faced this kind of problem.
What i saw was that the rooster got on top of one of the hens to do the "deed", then i noticed that the hen sat down and male after a while climbed down unsuccessfully. What i think the problem might be that as the rooster is quite tall and when he mounts the hen and the hen sitting down creates a problem for him to reach down and make contact.
The hen sitting is quite normal, some will mate standing but others don't. A lot depends on how interested she is and how heavy he is. Most of my hens don't mate sitting.
If he is at all able to sit down normally, such as you would see on the perch at night, there's no reason his height should stop him from mating.
Nothing wrong with what she did, unless he got into mating position and she didn't move her rump feathers and cooperate in the cloacal kiss, which some hens do when being pressured by a rooster they don't like.... But it doesn't sound like that's what happened, because that still looks like a successful mating even if it's not.
What did he do while standing on her?
Some roosters just can't do it, they're impotent, especially purebreds of show or rare breeds, due to inbreeding. I've had 'sitters' before that would get on a hen and then do absolutely nothing despite her waiting and cooperating. Maybe they'd attack her, just sit and maul her and not attempt to mate. Some had to be forced to get off of her or they would sit there all day doing nothing.
They're either deficient in instinct or reproductive capacity --- or both --- and I culled them out. I'm not breeding for show so I won't practice artificial assistance of males that have low to no fertility or capacity to mate naturally. The same cannot be said for a lot of show breeders unfortunately. But, not to tar all show breeders with the same brush, some also value hardiness, fertility etc. But those are big problems in some breeds and it often can't all be reversed in one generation.
Can you ask the breeder of these birds some questions about whether the parents had mating or fertility issues, or whether they were bred via artificial insemination? Some breeds need their fluffy butts trimmed, but externally it would still look like a viable mating. Sounds like it did not at all look viable to you though.
This is what i think of the problem. Any one else had such kind of problem or any remedy to fix it?
If you can tell us what he's actually doing, it will give us a clearer idea, but a male that isn't following through with mating is likely a dud and while you can resort to some extreme measures to help breed him, it's unadvisable because it is breeding on a detrimental trait. Given that you have imported him I am guessing you would rather try everything possible though.
I agree with Ridgerunner on a few points there, being that they're slow maturing and the vents may need trimming, however I've never had a rooster enforce dominance on a hen by mounting, I don't believe mating has anything to do with dominance despite the common notion that it does, and I've had plenty of roosters mate without sitting down or the rooster holding on to her head or neck feathers. What's 'normal' isn't necessarily the same thing as 'natural'.
Best wishes.