Click on any of the following for some background and an explanation of the technical terms used in the species factsheets and additional data tables:

• IUCN Red List Categories
• IUCN Red List Criteria
• Range and country distribution
• Habitats, altitude and migratory status
• Threats and impact
• Data quality and derivation
• Extinct species 
• Red List Index
• Generation length

Range and country distribution

In the species factsheets, territories in which a species occurs regularly are highlighted in bold, whereas territories where a species is a vagrant or occurs irregularly are not emboldened. However, all country distributions are held in IUCN's Species Information System (SIS) and are listed in the factsheet additional data tables. For seabirds, at-sea ranges are also included where these overlap with a territory's 200 nautical mile Economic Exclusion Zone (EEZ). The SIS also holds additional range data so that they can be tested against the IUCN Red List criteria. Some of these are also listed in the factsheet additional data tables, including the Extent of Occurrence, Area of Occupancy (where known), and the number of locations and degree of fragmentation (see IUCN Red List Criteria for definitions).

Occurrence status

A species occurrence status is coded into one of the following categories:

• Native (N) = The species is/was native to the area.
• Reintroduced (R) = The species is/was reintroduced through either direct or indirect human activity.
• Introduced (I)    = The species is/was introduced outside of its historical distribution range through either direct or indirect human activity.
• Vagrant (V) = The species is/was recorded sporadically, but it is known not to be native to the area.
• Origin Uncertain (U) = The species’ provenance in an area is not known (it may be native, reintroduced or introduced).

For each country a species is coded as native to, its occurrence is coded as one or more of:

• Resident/breeding = known or thought to be resident to the country, or to visit regularly during the breeding season and breed.
• Non-breeding = known or thought to visit regularly during the non-breeding season in the country. In the Eurasian and North American contexts, this encompasses 'winter'.
• Passage = known or thought to occur regularly in the country during a relatively short period of the year on migration between breeding and non-breeding ranges.

Country name - The names of states and territories are based on the names used by the International Standards Organisation. Political dependency is shown in some cases. These geographical designations do not imply the expression of any opinion on behalf of BirdLife International concerning the legal status of any country, territory or area, or concerning the delimitation of its frontiers or boundaries.

Maps - Maps indicate a species’s breeding/resident Extent of Occurrence (EOO) in red, and non-breeding EOO in green. At-sea ranges for seabirds are also indicated in green. Arrows highlight small EOOs where they may be missed at the scale shown. Individual locations are indicated by a black dot. Passage range is generally not shown, but for some species arrows indicate the general direction of migratory movement. Occasionally, important stop-over sites are included. Question marks have been used for very poorly known species to indicate areas where the species may occur or used to occur for Possibly Extinct species.