Sorry it’s taken so long for someone to reply. I think many of us first discovered that we had hedgehogs around when they were seen finishing off the remains of the bird food.
It’s difficult to give any suggestions without knowing quite how much bird food falls to the ground. I would try to ensure that it is kept to a minimum so that the hogs don’t eat too much of the not good stuff such as mealworms. Not sure about a little fence, that could cause problems too, depending on the construction. I think as long as there is not too much left it might be o.k. But if you use feeder saucers, etc. and there are ground feeding birds clearing up the dropped stuff there might not be too much. But, maybe you could clear up any excess that is left before the evening.
Then the hogs might welcome some hog food or cat/dog food, which would better for them.
Don’t forget to leave water sources out for the hogs 24 hours a day. I use shallow but wide plant saucers, so that the hogs are less likely to tip them over. Make sure they are not so deep that a hoglet could get trapped. The birds make good use of mine as well!