Depending on where you live, you will have different things to worry about.
I free range my ducks and chickens. When I was in Kodiak, somebody down the street free ranged her chickens. Way too many loose dogs walking about, bears and eagles everywhere - not an option I'd have wanted to consider if I had them then.
Here I have to worry about hawks. Haven't had an issue until last month when I lost my polish hen to a hawk
Our yard is fenced and we've not had the neighbor's loose dogs in the yard, so hopefully we don't need to worry about them, but if she ever gets one that likes to hop fences for feathered snacks, we'll have an issue (well, I'll have an issue and she'll have a much bigger issue as a result).
Night we have raccoon - I've not seen one, but we did see evidence of one once on the duck house roof. Also have foxes, coyotes, owls and who knows what else.
Mnie are locked up tight at night, but not always locked up until later. Chickens are sitting in their house when I go out and I have to herd the ducks out of their pond to go to their house.
We have plenty of places for the ducks/chickens to hide during the day, but the area of the yard they hang out in is kind of open - not far from good shrubs to hide under, but still open.