I had a live bird as bait, she was put in so if the fox did go in the trap it wouldn't be able to get her but it never went in but tried to dig under the trap.
I put a camouflage tarp over a live trap and some branches on it too. The fox and a coyote walked all around it but wouldn't go in. I had a live bird in a cage inside so the predators couldn't get it and they still didn't go in. After a kill I put the dead bird in and nope, they wouldn't go into the trap.