Foxes: Why are they visiting?

We have at least two visiting foxes that trip the Trail Camera at least a couple of times a night. The question that I have started asking myself is why are they visiting? .

Fox checking out grassy area at 2:20 am, February 22nd

The foxes often snuffle round the grassy area shown in the image. Are they trying to smell out food, or checking to see if another fox has visited recently? I've had the camera out a number of nights but yet to capture any encounters between the foxes. This doesn't mean much as I think that they are most likely to meet at the entrance to the garden. One or twice they have moved very quickly across the screen but whether they are running towards or away from something, I don't know. I

They could be searching for food. According the the Collins Field Guide to Mammals, foxes are opportunistic feeders.  It says that their diet includes: rodents, birds, insects (especially beetles), eggs and earthworms. We have found odd holes in the ground after visits and they are likely to be digging for worms. The guide explains that they also scavenge at bird tables and compost heaps. We have both. So there is a certain amount of food they can find while in our garden.

I'm not sure why the foxes visit. I think that, at this time of year, they might be finding a small amount of food and that is the most likely reason. Maybe they have a regular route and we happen to be on it.