Responses need to be tailored to your situation.what bait should i use to trap it
If you can, then pen up remaining birds. If you have a firearm and it is appropriate for your location and you have the time, then setup to shoot the fox when it comes back. In my experience the Red Fox is consistent and punctual with its visits so being ready may not be all that difficult unless you are at work when fox visits. Look into building a coop with run for these situations and consider putting up an electrified perimeter of some sort.
Resources you have are not known to most so that can greatly impact your options for preventing subsequent losses.