Generally, pinyons, mesquites and oaks factor into this usage. The base of pinyons are occasionally used. It was carried mostly by white firs, pinyons, junipers, and sagebrushes. Nest failure is "high" during years when pinyons do not produce seeds. Biome classification recognizes that pinyons require twelve inches of precipitation annually. Occasional two-needled pinyons in northern Baja California are hybrids between single-leaf pinyon and Parry pinyon.