This article is a parent page for a series of articles providing information about endemism among birds in the World's various zoogeographic zones.
The term endemic, in the context of bird endemism, refers to any species found only in a specific area. There is no upper size limit for the geographical area. It would not be incorrect to refer to all bird species as endemic to Earth; in practice, however, the largest areas for which the term is in common use are countries (e.g. New Zealand endemics) or zoogeographical regions and subregions (West Indies endemics).
Birdlife International has defined the term restricted-range endemic as any species whose historical range is less than 50,000km².
Endemism is particularly notable when not just a particular species is confined to given areas, but a whole higher-level taxon (e.g. genus, family or even order).
Birdlife International has defined the concept of an Endemic Bird Area (EBA). This is a region of the world which contains two or more restricted range species.
To support this, they have also introduced the Secondary Area concept, for areas which contain one or more restricted-range species.