The Western Palearctic is the region composed of Europe, the Middle East, and North Africa. Its exact boundaries differ depending on the authority in question: traditionally the definition as per "BWP" (Handbook of the Birds of Europe, the Middle East, and North Africa: The Birds of the Western Palearctic) is used, and this is followed by the most popular Western Palearctic checklist, i.e. the Association of European Rarities Committees (AERC) list.
BUBO Listing supports the AERC list plus some alternate Western Palearctic checklists, and official country lists for most individual countries within the region. (It is intended to support all countries in the future.)