It don't think it hurts them. I have 19 gigantic water oaks encircling my house. (One reason I bought this property although I may regret that if I outlive the oaks) Chickens try to eat these little acorns, then spit them out. Noticed they ate crushed ones on drive, so ground some in an old blender to give for a snack. Many farmers in the US fed their chickens largely on acorns during the depression. Research online says you can use acorns for a large percentage of chickens' protein needs, although when I read of some possibility of toxicity of the shells, I started just blending them enough to barely crack the shells and let them pick out the "meat"One of my roosters was particularly wild about these, and all partook but none ate huge amounts although they could. I only did this off and on for a month or so, when the acorns were freshly fallen. The great thing about the water oaks are that they attract jays, who dearly love the acorns. The jays chase off hawks and imitate the cries of hawks in order to scare them away from their babies.