That looks like coyote. I think I see the nail marks. Next time put a ruler next to the track before photographing since size helps with identification. It is hard to get clear tracks when the soil is rocky. I have the Peterson Field Guide to Animal Tracks. It is fun trying to figure out what makes the tracks. Not so fun having it take your birds, though.It probably was a red-tailed hawk. They are the biggest around here, I'm pretty sure. They are beautiful, and I would hate to kill one. Wildlife is too important to keep around! We have a Cooper's Hawk that tries to catch wild quail in our yard. He doesn't seem interested in the big chickens. I just put the littles out in a new coop (super deal on craigslist!!!), but they are covered, and I bring them in the shed at night in their box. While I was collecting them at dusk the other day there was a massive great horned owl sitting in the Palo Verde tree above the coop. Same night a pack of coyotes started whooping (don't know what else to call it) either in our yard or the neighbors. I ran out in my tank and undies and bare feet to run them off. Glad it was 3:30 AM so the neighbors couldn't see me! I didn't see how many there were as they ran off before my eyes had a chance to adjust to darkness. From last week, here is a paw print of the predator that took away one chicken (Crannie, my fave.) and Pepito, the duck:
Another view:
