We normally throw scratch grains to our feral chickens near the house but in a rocky/muddy area. But when it is raining hard the area can get flooded temporarily and the chickens often shelter under the eves of the house. We sometimes through the scratch grains on the concrete driveway under the eves. The chickens don't seem to mind but I wonder if pecking at food on concrete hurts their beak or causes other damage. Note, we only do this when it is raining hard enough that the chickens are sheltering and would otherwise not eat. Any comments?