I posted this as a response in Snakesmum blog. I am moving it to its own by  request.

Your post reminds me of a little hen we use to have.
Now mind you I am a cat and dog person but the
neighbors had penned up chicken and one day let them go
Naturally they came to my house.

I like you enjoyed these cute entertaining little critters.
I like you also have a cat door.
We have many cats, and dogs as well. Our cats can come and
go as they please through the cat door. We often get strangers
that manage to come in and some never leave. But that is another story.

When you have cats you must have litter boxes. The 5 I have located
through out the house all have covers on them. One is in my bedroom.
This particular little box is very rarely used. It is off in a dark corner.
So imagine my surprise when I lifted the cover to scoop I find a beautiful
blue egg. My little aracana found this perfect spot to lay her eggs.
Now mind you, this little girl would have had to navigate the cat door.
AND... gotten by the dogs. So the fact that she got in, looked around
and found this spot is simply fascinating to me.
What harm could she do?

Everyday she added to her clutch. After about 20 eggs were laid it was
time to sit. In the middle of the night you could hear the litter gently being
moved, she was a good mother stirring the eggs ever so often. Once a day
she would sneak out of the house to eat, drink and poop, then sneak back in.
Never did she make a mess. Weeks later in the middle of the night the babies
started hatching I could hear the little darling peeping. I waited a day to make sure
that all had hatched and then picked up the entire litter box and moved it outside
to a waiting pen.

So about those chickens in the house...
I have been there and done that, and I enjoyed it.