I had a strange experience and was wondering if I actually understand. I had lost an entire flock to a bobcat a couple of years back. My new flock has had no problems, so far. Yesterday I saw the silhouette of a cats head at the top of my chicken's playpen (2 acres ) My 4 ISA Browns also spotted it. I could not tell if it was a stray cat, wildcat, or a bobcat, the ISA Browns all stretched up their necks looking at the animal, started an odd honking, then all gathered and began advancing towards the critter. I called them and they ignored me, very unusual since they ALWAYS come running when I call (took me 2 years of daily work to get them trained) the animal ran away as I moved towards it so I never got to see what it was. As soon as it left the 4 ISA browns came back and headed to their coop. So do some chicken breeds mob predators? Or were my birds just dumb.