Most owls eat only field mice, shrews, voles and other similar fairly small vermin they can swallow whole. The only owl that is actually big enough to kill a chicken, let alone a turkey is a Great Horned Owl. They ARE however located all over North America year round, and they ARE very good hunters and wouldn't hesitate to go for a turkey... though they have quite a wingspan (3 to 5 feet across!) so a pen or run could interfere with them quite a bit.
As someone said, any of the critters the OP listed could get them though I agree that I thought muskrats were mainly vegetarians too, but I read they ate frogs and mussels etc. I don't think they hunt or would kill chickens. Mink or weasels on the other hand WOULD! We live right on a river and there used to be a mink farm in the area... that released some when they went out of business, gee THANKS for THAT!!! Yes, I've lost some over the years to mink. No I don't have a coat now!
Here's a list I made for another site I belong to, maybe it'll help a little. Some I've put in from personal experience, some from the experience of people I know and trust, some from reading though I'm pretty sure of the sources too.
Dogs, Domestic Cats, Coyotes, Mink/Weasel/Martin, Raccoon, Raptors (Hawks/Eagles /Owls), People, Fox, Opossum, Skunk, Bear, Lynx, Mountain Lion, Cougar. I haven't said much about the lynx etc below because I don't have much real experience with them (I lived for 7 years where they were seen but they're very shy).
Dog > By FAR!!!!! The Number one danger for most backyard flocks! Many birds in a flock will be mauled, killed, injured, dogs will chase and kill chickens for no good reason, to them its mostly fun. Theyll rarely eat any. Poorly kept dogs are a menace.
Coyote > Somewhat like dogs, but theyll come in pairs usually and scatter a flock, kill several because they get in a bit of a frenzy over all the wings and squawking etc, but then take away a couple out to the bush to eat. Once these guys find a likely source of food, theyll return the next evening and the next and again and again.
Domestic Cats > A feral cat could possibly kill a chicken, especially in an enclosed area, but its not easy and not common. Most people blame cats because they dont realize how many raccoons, opossum, coyotes and fox are actually active in and very near cities and towns. Most well fed house-cats are pretty lame at trying to catch a chicken let alone kill one. Its not impossible though.
Various wild Cat species > I have limited experience with cats, I lived where Lynx were occasionally seen but they are very shy so never bothered us. Mountain Lions, Lynx, Bobcat, Puma etc will all take chickens if or when they can. They will carry their prey off to a safe spot to eat it where they feel safe. Once they find a source of easy food they tend to visit again periodical for another try.
Mink/weasel/martin > Several killed, a lot of small bites, some portions eaten, especially heads and bellies. Mink do kill animals much larger than themselves and are incredibly fierce for their size. I have these since I live on a river
they're tricky to protect against, smart, agile, sneaky and hunt all hours of the day and night.
Raccoon > Several birds may be killed or just one. Raccoons will often just eat the heads and crops. Because of their very dexterous paws, if a raccoon can't cant get into a coop or enclosure but can reach a chicken through a fence or opening, it will grab a chicken and hold onto it while it dismembers it. (yeah, gross I know)
Hawk > One bird gone, a pile of feathers in an open area. Other parts nearby, sometimes only head eaten, depends on time of year (feeding young etc). Not all hawks will kill chickens, so dont get worried about every sighting. The most likely ones are of the group called, Broadwing Hawks which is a larger type of hawk that includes: Red-tailed Hawks, Red-shouldered Hawk, Swainsons Hawk, Rough-legged hawk, Ferruginous hawk and also, the Goshawk which is mostly in the very northern tier of the US and up into Canada.
Owl > a lot like hawks, but owls usually (most say exclusively) hunt at night. IMO they also hunt in the very early dawn, and at dusk too. Most owls eat only field mice, shrews, voles and other similar fairly small vermin they can swallow whole. The only owl that is actually big enough to kill a chicken is a Great Horned Owl. Keep your chickens in a coop at night, theyll be safe from these guys.
People > Several birds gone, no sign of predator
yeah, it happens.
Fox > Several birds killed, usually by a broken neck, only one taken away. You may find part of a corpse and/or feathers nearby, they do take away and dont like to eat in the coop.
Opossum > One or two birds dead, mauled. Mostly bellies eaten.
Skunk > Much like an Opossum, and they love eggs. Biggest clue is the smell of course, even if they don't spray, they'll leave scent.
Bear > door gone off of coop, fence destroyed, etc. you all knew that right?
