Yes, in fact it is sometimes recommended that you give a pet bird ground eggshells when they are in egg-laying mode. it helps rebuild their calcium levels.
Is Egg Shell Edible?
They are eddible, as in you will not die from eating them. The shells can run the risk of ecolli and other bacteria if not clean properly. The egg shell is approxamentaly 95% calcium carbonate which is commonly used in medicine purpose like acids and calcium supplements.