Insect and Spider Identification: Rocks? excreted Seed Pods? Or what?, 0 by BeverlyGarden

BeverlyGarden wrote:
I have just noticed the outer layer of my mature lilac bushes have been stripped at their bases. Even more unusual are what's been left behind. These are hard as pebbles, a 1/4" in size and each has a small bore hole. They are very distinctly piled only around the base of the lilac stems that have been eaten. Can you help me identify what's getting at my beautiful lilacs, and what I need to do to protect them from further damage? I don't want to lead anyone to conclusions, but I do have a few wild rabbits in the area.