Send a birthday message to the camper you just sponsored - it doesn't need to be long, just a note that says someone cares! Sometimes this is the only birthday card they receive all year.
E.g. "Happy Birthday! You are special to God! Enjoy your time at Camp David. I'll be praying for you! From, (Your Name Here)"
They will receive your greeting in a card with their birthday present during the Birthday Party event at camp.