This last year was hard on my flock, we started with 18 hens, 4 ducklings, and one rooster... currently we have 3 hens, 2 ducks, and the same rooster, plus about 20 peeps and 2 guinea cheaps. We've fenced in a quarter acre with 6' 2"x3" fencing with 2.5' chicken wire ground skirting. For over a year this seemed to have fixed all predator problems; except for the aerial kind, but our vigilant rooster keeps them safe from everything but the occasional falcon.
Unfortunately, from mid-May through July something (we think raccoons) took out the flock. We added a security came with an ability to hit an alarm at will and does real time viewing, and motion activated flood lights.
However, we think the two decades old boom box that's serenading the flock 24x7 is really keeping everything away. The station we set it to has a talk show for about 3hrs a day and music plays the rest of the time.
Our four oldest nest high in the trees so I can't lock them up in the coop for safe keeping... we're hoping this will change again come winter.