I lost 24 chickens (21 hens and 3 roosters) last year to foxes. I managed to shoot one of the foxes in the act but that didn't stop the other foxes from helping themselves. They got so bold that they'd snag my chickens in broad daylight. This was all within a month.
The rabbit hunting has been crappy the past year or so too so it's just the natural cycle of things. Lots of food for predators = lots of predators. Once the population of their prey goes down the number of predators drops again.
I keep my chickens in a shelter at night and let them roam free range during the day.
Hopefully the foxes won't be so bad this summer.