You know that is so interesting you say that. At my old house I had lot of bumblefoot occurances and I had a huge gravel driveway. Now at my new place this year I only had 1 case and they don't have access to a gravel driveway and I have 2x the birds and I had wondered if that was why.
My vet told me to keep them off the gravel. I suspected the blackberry bushes were the culprit because they often hang out there. But then read where people plant them for their birds. It will be very difficult to get them to stay off the gravel. It goes up to the door and that's where the snack come from. Also, their favorite foul weather shelters are off the gravel.