Adding New Chickens

[Awestruck]

Last year, someone dumped a rooster off at the neighbor's house, and it ended up in our yard. It stayed there and adjusted well. We had him for 3 months and he was killed by a predator. (We had not gotten the chance to build him a place of protection yet).
Last month, a hen came in our yard. Not sure whose it was, but it never left our yard. I would take care of it and hoped that someone who owned it would be looking for it, but nothing. We fed her, etc. but one morning she was no longer here. No trace of her either, except a couple of feathers.
(I ordered a coop just for these stray chickens when they come in and decide to live here).
Now, the big questions. Another hen has now decided she wants to live here. It could be the neighbor's. I don't know. They let their animals roam everywhere and I never see them out to ask them. Anyway, I want to take care of this hen and if the owners come by, I will have taken care of her while she was missing. But if we never find out whose it is, I will keep her.
Here's the problem: She found her way into the chicken yard, even though we have it blocked off. The chickens are ok with her, but, I don't trust them, especially the bullies (the barred rocks). Now this hen has gotten inside the coop. I don't know what to do with her. The rooster is going nuts in the coop for some reason, perhaps because I have the back door of the coop open?
When I go out, I want to put the chickens in the pen/coop. But now that this hen is in there, I don't know what to do with her. I was going to leave her out and open the gate so she could leave the chicken yard if she wanted to. If she belongs to the neighbors, she can get back into their yard through an opening in the fence. Not sure why she wants to be part of the gang and I want her to be protected in the mean time from predators.
Can she go in the coop/pen with the other chickens or will she get destroyed and how will I know (I don't want to find out the hard way)? I don't want to make a mistake I will be sorry for later on.
(She is an Americauana and almost looks identical to one of my hens. She is gentle and probably on the bottom of the pecking order, like mine are).

 

[BY Bob]

You should always worry about any new chickens bringing disease with them. It's a good idea to quarantine them. However it seems like this one has already joined your flock of her own free will. I'm not sure from your post, is she mingling with the others? If she is, the deed is done. Pecking order issues usually work themselves ot with no one getting hurt badly as long as there is space for them to escape and not be cornered. Is there room for the newby to get away?

 

[Awestruck]

The new hen was inside the coop today, but she could get out. Some of the girls snapped at her occassionally but there was enough space for her to run away. I was glad she got out of the pen/coop and I don't know if its time to let her stay in there overnight yet. She didn't join them when I put them all in tonight, but she is in danger because she insists on staying in our yard, and I don't have any way to protect her during the night.

 

[BY Bob]

Have you approached your neighbor and asked if she is theirs? I don't think she will go back on her own. She has decided your house is a better place to hang out at. If you remain half way committed I am afraid something bad is going to happen to her. Can you put her in your run but not your coop and would that provide any protection at night? You could let her out before you open the coop for everyone. I don't know your setup but with mine I can segment sections of my run from the coop and my run is pretty fortified.

if you can't do that, I think you either need to adopt her or find out who she belongs to and return her. Where you are now will not be healthy for her long term.

I wish I had a better answer for you. Please keep me posted. Can you snap a photo of her? I'd love to see what she looks like.

 

[aart]

It could be the neighbor's. I don't know. They let their animals roam everywhere and I never see them out to ask them.

Knock on their door and ask.
I'd be ticked off if neighbors animals were regularly in my yard, possible infecting my flock.
I've had a few strays, I catch and crate them and give them away.

 

[BY Bob]

Knock on their door and ask.

You are just a little more blunt than I am. I was trying to lead them there. Thanks for adding your thoughts. I always appreciate your point of view.