We've been keeping chickens too for several years. We had a great chicken massacre earlier this summer, by uncertain predator, that killed off the whole bunch except one. (We only had 7 or 8 at the time.) I'm not one for naming chickens, but we call this one Lucky. I guess it could have been raccoons - that's our usual problem - but they usually just take one each night until you fix the fence problem or get better about shutting the door at night. Whatever it was left a big ugly mess of dead and mortally wounded birds, which is decidedly un-raccoonlike. It looked more like coyote damage, but no tracks, no evidence of digging in, feathers on the top of the fence. We do have cougars, bear, and now wolves (thanks a lot Dept. of Wildlife) here, but I would think a larger animal like that would tear the coop and/or fence apart. I don't know much about bobcats, but I don't think they hunt in packs and it seems like an ambitious project for a solitary cat. Very strange.
My current dilemma. It was too late in the year to get chicks. I now have one chicken. Do I want to run extension cords out to the coop, run a heat lamp all winter, heat water all winter, snow blow across the yard to the coop all winter, for one chicken? Me thinks not. Would one chicken even stay warm enough all by itself? I think I'll give her away and regroup in the spring.