How to raise Backyard Chickens: [CHICKENS-101] Its official, we have foxes...

Ugh... in the last week we lost a 16wk old Americauna AND on another day our Rooster got into a scrap with something ( we didnt see it, but heard the ruckus, Roo came stumbling out of the cornfield. He was beat up but fine. This happened at 5pm broad day light)
We did a count when they were all in the coop for the night ( they free-range) and realized we were missing a hen. ( so two birds within a week)

Went back to the "scene of the crime" poking thru the corn field carefully and there as a load of feathers that indicate that our RIR hen is gone forever...

Well.. we have certainly been lucky, its been almost exactly a year before we had any problems.

At this point we didnt know what we were dealing with. We have never seen a loose dog or coyote but I had seen a fox about a mile down the road in the last few weeks.

This morning after we got up and were drinking coffee we could hear the distinctive cries of a fox. And its close, perhaps in the grove of trees behind our house.

Hubby went and got a trap, and everything he will need to disquise it. He thinks there may be a den in that grove of trees ( the same ones they take refuge from hawks in, sigh)

Mind you they only free range when we are home ( so after work on weekdays and on weekends when we are home) But that enough for them to do their evil worst.

I did say to hubby that IF after we trap/remove a few we are still getting losses we will have to consider putting up a "day run" behind the coop to extend their area and have more room. Right now they have a 8x8 coop and an 8x16 run (extremely well built) But if they are going to have to stay cooped up more I would like to add another 16x16
We have 1 Roo, 8 1yr old hens and 13 babies (about half of the babies will be culled in the next 5 weeks or so) so in the end that will leave us with 14 chickens

the reason I am posting this is to ask... once we trap a few foxes, what is the prognosis for more to show up? is there something we can do to prevent more? or once it starts our only option is to pen?

Thanks for all your input and advice.
Lisa SCentral WI