An Endemic Bird Area (EBA) is defined as an area which encompasses the overlapping breeding ranges of restricted-range species, such that the complete ranges of two or more restricted-range species are entirely included within the boundary of the EBA. This does not necessarily mean that the complete ranges of all of an EBA's restricted-range species are entirely included within the boundary of that single EBA, as some species may be shared between EBAs.
Restricted-range species are defined as all landbirds that have had, throughout historical times (since ornithological recording began after 1800), a total global breeding range estimated at below 50,000km2. Species with historical ranges estimated to be above this threshold, but which have been reduced to below 50,000km2 by habitat loss or other pressures, are not covered as EBAs should represent natural areas of endemism for birds. In the identification of the current list of EBAs, restricted-range landbirds that have become extinct since 1800 were included to help identify areas of high concentrations of endemic species.
For full details of the methodologies used, please see:
Stattersfield, A.J., Crosby, M.J., Long, A.J. and Wege, D.C. (1998) Endemic Bird Areas of the World. Priorities for biodiversity conservation. BirdLife Conservation Series 7. Cambridge: BirdLife International.
New information on bird range expansion and contraction becomes available regularly, and the 1998 EBA inventory will be updated in the near future.