While I'd never put one in my pen (I don't need extra protection, because I use my dog as a guardian), I would believe an Asil rooster (also spelled Aseel) would be a good guardian for your hens. You can only get one, and he should probably be your only rooster, but they should be able to kill/maim just about anything (excluding things like dogs/bears) that tries to get into your coop. Asils are fighting birds, and even the hens are horribly aggressive, and, in my experience, rather intelligent. I've got an Asil hen that has managed to draw blood, and she's broody at the moment. I tried to use a piece of straw to distract her so I could grab her and put some eggs under her, but she ended up pecking my hand instead of the straw. With our Asil, as long as you don't try to mess with her, she ignores you, so you shouldn't have to worry about her attacking you just for going in the coop...
In all honesty, if you want a good attack bird, I'd go with an Asil hen, as they know how to fight, but shouldn't hurt your other hens (unless they try to move in on the Asil's nest.) Asils were bred to fight, so they are very good at protection, but that also means that you need to be able to deal with their aggressiveness.
In my experience, the Rhode Island Red roosters tend to survive best (after the Asils). I can't say that my RIR was a good guardian, but he survived every attack we had on our coop. The one unfortunate thing with our RIR though, was he was a bit too harsh on my hens, especially when there was another rooster in the coop. We had multiple hens end up with dislocated legs, and ended up having to put the rooster down to avoid having him hurt any more of my hens.
In the end, if you want to put a bird in with your chickens to keep your hens safe, I'd get an Asil hen. She won't attack your other hens (as long as they stay away from her nest when she's broody), and she's aggressive enough that, should something like a weasel or a raccoon get in, she'd probably attack the intruder, especially if there is a light in the coop so she can see the attacker.
the older rooster watched over his 3 hens, the younger rooster kept to his 7 hens. My question is, since the older, alpha rooster is no longer, will the young rooster (6 months) take over protecting the other 3 hens? Or should we look into getting another rooster that is older & knows what he is doing? Would really appreciate any advice. Our chickens are our kids! We don't like leaving them unattended by us or one of the dogs since this happened.
