Add leaves to the run and that will attract worms, bugs, spiders, and a bunch of other little treats. It also makes good composting so you don't have to clean the run so often. The chickens will even dig and stir it up for you! Plus, like many other people on here said, foraging is a lot healthier for the chickens. Adding leaves to the run will let all the little bugs and stuff get in there, without the predators.