IMO I say owl only because most other predators in my area I can shoot them and they will not come back (including the 2 legged kind) But not the owl or hawk. I have heard Weasels are pretty bad also.
In California I lost a few to possums. We've since moved to Maryland and lost a flock to a fox. We also had a hawk get one. I'm fighting mites right now and it's turning in to prime predator season, so I'm getting nervous. I hate to keep them locked up when they love to free range.
We have all / most of those predators here in Northern NH . I lost a cat last yr & just a few wks ago. Not sure what got them. I have seen a chicken hawk around last fall & last wk. Fingers crossed no chickens. I can't put a top over the yard it's way to big 200' of electric mess fencing.
a few yrs ago something got my neighbors hens. took their heads off. Now they have a very small pen with under ground fence & a top. to small for as many birds as they have & 2 ducks.
We have had our chicks outside since August 6th. They are now just a little over 3 months old. The only encounters we have had with a predator so far has been with red tailed hawks. The 1st time, a juvenile that was unsuccessful ( we now have a Silver Laced Wyandotte named "Lucky Chicken"
) and just this past week, with a very large adult, who ate our poor buff laced polish rooster. We also have foxes, coyotes, skunks, racoons, owls, weasles and fishers that I know of, but I suspect our dog's scent keeps them away? Or have we been lucky?
When I put mine in I didn't think I would have a problem with predators. Little did I know that skunks and raccoons could be a problem at the time. The skunks were easily beaten - but that raccoon caused me all kinds of problems. I live in town so I couldn't shoot the thing.
Finally I visited a nearby farm for some advice and got one of his dogs off him that was raised with farm animals. Shepherd doesn't bother the chickens at all - he's really used to other animals and is actually very protective over the animals and people living at my house.
The raccoon has moved on to other & safer hunting grounds. I haven't had a problem since.
i lost an entire flock of 15 plus a massive roo all in one night with only a very tiny lil openning in the pen to a weasle. he sliced the throats, drank blood of every one of em. then left the bodies for us to find in the morning
it was pretty sad. the next time, we openned the door to find a fox standing about 10 bodies, growling at us. Mangy as sin, he got shot and buried 3 feet under in the middle of nowhere.
That was a rough year. and the end of that flock.