How do you clean makeup off white feathers?

A product such as Citra-Solv is a natural degreaser, and perfectly safe to use on a birds feathers. A few drops of this rubbed into the stain using your thumb and index finger should clean it well, then wipe it with a clean towel or wash cloth in the direction of the feathers.

You may also try 1/4 cup of baking soda to 1 quart water, applied with a clean towel or cloth in the direction of the feathers, or by rubbing with your thumb and index finger. Use clean towel or cloth to wipe dry.