This evening I tried again to trap one of the several black cats on the base. I was successful, although not the way I’d hoped.
First I trapped the same cat that I trapped a couple of weeks ago. I had her spayed the first time, of course, and didn’t need to trap her again. And despite her terror the first time she found herself with no way out, she went right in that trap again. “Not the sharpest knife in the drawer, are you?” I asked her. She didn’t respond. Too ashamed of her inability to resist tuna, I suppose.
Next the elusive cat that I was trying to trap the last time I posted sauntered coolly into the trap, gobbled up the tuna, and exited without setting it off. Again. Which is all for the best, I suppose, as I am pretty sure she is no longer pregnant. Her nursing babies are going to need her for the next few weeks. I did finally get a good look at her and she is magnificent. Long charcoal fur with a full mane. 
Finally the third and fourth cats appeared. One is clearly a Tom, with the telltale fat cheeks containing all those pheromones. The other is a fairly small, smooth coated, and of course, black cat. She couldn’t resist the tuna either, but she is not so wily as the other. As soon as the trap closed, I rushed her to the vet, and he helped me confirm what I suspected: she is nursing. I took her right back and released her.
It looks like in five or six weeks I will have at least two adult females, an adult male m, and who knows how many kittens to TNR or socialize. Until then, I leave them in peace. I, on the other hand, will be diligently seeking an elusive peace, knowing that all those little souls are struggling to stay alive in a hard world. Say a prayer.