I get at least one fox call a summer, sometimes 3 or 4. Not many. It's usually around June, when adult fox are feeding pups and they have kind of cleaned up a lot of available wild food, and the pups are getting both bigger and hungrier, so the fox get more desperate. They then will get bolder and come right into a yardand nab one, esp. if the chickens or ducks are free ranged and not behind screen. They'll sometimes do this in plain sight of the owner.
I make two dirt holes near the approach area, one baited with Rob Erickson (On Target) Golden Maze paste bait, a great summertime sweet corn bait as it's heat and rain resistant and also takes a week or more to dry out. Everything likes this stuff, esp. fox, skunks and coon. The next set is baited with On target's Honey Gland. One hole will have just a touch of red fox gland lure, the other a touch of red fox urine. Usually have one or both fox the first night.
Fox usually sneak through thick vegetation for cover, then charge out into the open and grab a bird, and take off with it. If they're successful and not disturbed they tend to use the same ambush spot so after a couple hits they leave a slight but discenible trail through the thick weeds and grasses. Hang a 5/64 or 1/16 snare, loop about 6 inches wide, with the bottom 5-6 inches off the ground, depending on how thick the vegetation, and if they use the approach again you have them. Snares are deadly. Don't do this if the customer has cats roaming around, might snag one.
Sometimes poultry eating fox get really habituated to people and can be fairly bold, letting themselves be seen standing in plain sight 20 yards or so away. Through the years I've shot about a dozen or so of these fearless fox by using a game call, dying rabbit or fawn bleat. They run out in the open and stare at you, and a 12 gauge with copperplated #4s or copper BBs will dump them.
If its July and the pups are big enough to be out running around, but still hanging around the dn, the whole litter can be caught in a night or two, with footholds and dirt holes around the den, baited again with Golden Maze or Honey Gland. No lure or urine needed, the pups are always hungry and easy to catch. I'm sure other commercial summer ADC paste baits will work too. I use the smaller #11 double longspring on pups, no foot damage. I've had landowners request the pups be taken to a rehabilitator.
Adult fox feeding pups will kill poultry up to a mile away from a den, and lug it back. A couple times, in late may or early June, when pups are still very small, I've found the den within a couple hundred yards of the chicken yard. I got on my knees and rubbed my hands all around and in the dirt around and in the entrance, to stink it up, then peed down the hole. The den was abandoned next day. Don't know how far they moved, but the killing stopped, which was all that mattered anyway. Don't know if this would work every time.
Most poultry predation by fox is done by mid to late July because the pups are mobile enough to feed themselves a lot. Fox are leery of people and usually only prey on poultry when desperate. Raccoons, though, will do it all year, right up to hibernation. They're not feeding pups - they're feeding themselves. In my experience here, well over 75% of my poultry predation calls prove to be coon. Fox get blamed for a lot of coon suppers. - Bob