Chocolate is ok - in very small doses.
You are correct that very small amounts of chocolate will not kill your bird. It takes approximately 1 pound of chocolate to kill 7 pounds of dog, cat, bird, human, ferret, etc. However, MOST of the chocolate we eat is not pure chocolate, or cocoa, so there is some leeway. Coke, Pepsi, Mountain Dew, tea, coffee, etc. should also not be given to birds for the same reason.