Hello.  Hope you all can just give me some advice.  I'm the mother of a
former stray someone here was nice enough to call a "grand old cat."
She definitely is.

But she is old.  We live in the mountains, and since she's a former
feral, just TRY to keep this cat in during the summers.  No way.
(She's at least 13 and probably more like 15.)

Well, since the spring, two specific cats--gorgeous--one white with tan
ears, one unusual black-and-white (like a cow!)--have been appearing
from time to time on our land.  At first I thought they were strays,
and since I'm older, with a handicapped old family member, I set a trap
from our non-kill shelter, 'cause I don't want any strays to suffer.

Now that it's real hot, these two cats (I notice a pure black kitten
with them, but only this one kitten) are actually coming into our house
and fighting with my old buddy.  This morning I almost had a heart
attack, 'cause it seemed as if they were going to bring the fight up
into our actual house.

If these poor animals are strays or ferals, I have to catch them before
the weather starts getting cold.  We have fantastic non-kill cat
shelters where I live (and I support them).  They are very thin but do
not look neglected at all.  In fact, I saw them both on the porch of a
very wealthy neighbor's porch accidentally, back in May.  I concluded
from this that they are just not "collared."  Neither is my cat (who is
microchipped).

So what do I do?  I can't have my old buddy living in fear of them, and
maybe they just want to play, but she is old and obviously doesn't take
kindly to them.  I do not know the name of the neighbor whose porch I
saw them on, or even these people's names.  (We live in one of those
woodsy developments where people guard their privacy, and I *mean* it.)
I suppose I could mail a letter to their Post Office box to see if the
cats are theirs.

Anyway, if cats 1) look good (but thin), 2) have not acted
aggressively, but 3) roam a neighborhood so much that other people
notice them, how do you tell if they are strays?  If these neighbors
ignore my letter (believe me, I have called lots of people in the
neighborhood trying to find out if they're homeless), should I catch
them and just hope they're chipped?

I'm at a loss and want to do the right thing, and unfortunately, the
right thing just can't include taking them in.  Thank you and God Bless.