All five of those were killed this morning between 8:00 and 10:30? Or was it six? Or were some of those killed over the past several days? I feel like I don’t understand your timeline.
Practically any animal will hunt during the day, even though they may mostly hunt at night. Right around dusk and dawn seems to be really high risk areas but I’ve seen plenty of foxes, skunks, bobcats, and coyotes hunting during the middle of the day.
Wirth just the head missing, I immediately think of owl, hawk, bobcat, mink, or other members of the weasel family. Raccoons are also a possibility. Where you are an eagle may be possible. An owl, hawk, or bobcat is not likely to kill more than one at a time, two at the most. They often eat some at the spot but can certainly carry a body away, especially if they have young to feed back at the nest or den. Bobcats normally bury the remains to save for a later meal. If those roosters' bodies had stuff scratched over them like something was trying to bury it, suspect a bobcat.
My experience with a fox is that it takes one chicken from ambush and carries it off, leaving only a few feathers, though some people on here have had a flock practically wiped out in one fox attack. Predators don’t always do what they are supposed to. That’s part of what makes it hard sometimes to be sure what is causing the problem.
Coyotes don’t feel right for what you describe, but maybe. Just taking the heads doesn’t sound right.
I don’t think it was a skunk. They are not likely to get a free ranging bird, certainly not several at once. They normally maul the carcass pretty badly.
Did you see any poop around that might help identify the predator? If you can find poop, there are charts online you can use to help narrow it down a lot.
Did you examine the carcasses left for punctures or claw marks? If you can find scratches from the claws or punctures form talons of a bird of prey, you can narrow it down a bunch.
Sometimes when several birds are gone at one time, it’s not a normal predator but instead a mother teaching her cubs to hunt. I’m not sure what that might be this time of year in Idaho. Maybe a bobcat?
Obviously I don’t know what that was. With just the heads missing on some and others with the entire body gone, and it n=being several at one time, nothing really sounds just right.