Chile de Árbol Chili Pepper. 15,000 - 30,000 Scoville Units. Capsicum annuum. The Chile de árbol, Spanish for tree chili, is a small and potent Mexican chili pepper which is also known as bird's beak chile and rat's tail chile. In cooking substitutions, the Chile de árbol pepper can be traded with Cayenne pepper. The peppers are a bright red color when mature. Chile de árbol peppers can be found fresh, dried, or powdered.