Categories of extinct and threatened bird species

Virtually all bird species included in this ZMA catalogue of threatened and extinct birds were among those listed in the recent book on Threatened Birds of the World published by BirdLife International (2000). The categories of threat used in the ZMA catalogue are largely based on this book and are defined as follows:

Extinct The species has not been observed for the last 50 years.

Critically Endangered or Extinct The species has not been observed for 10-50 years and is presumed to be extinct or very rare.

Critically Endangered The species shows an extremely rapid decline (of over 80% in 3 of its generations or in 10 years), and/or the breeding range of the entire species is extremely small (less than 99 km2), and/or the available suitable habitat for the species is less than 10 km2, and/or the population of the entire species is either tiny (less than 50 individuals) but stable or extremely small (50-249 individuals) and known to be declining, and/or the range is heavily fragmented with virtual absence of gene-flow between the 2-5 subpopulations left and all subpopulations are below 50 individuals each.

Endangered The species shows a very rapid decline (51-80% in 3 of its generations or in 10 years), and/or the breeding range of the entire species is very small (100-4999 km2), and/or the available habitat is 10-499 km2, and/or the population of the entire species is either extremely small (50-249 individuals) but stable or very small (250-2499 individuals) but known to be declining, and/or the range is heavily fragmented with virtual absence of gene-flow between the 2-5 subpopulations left and all subpopulations are below 250 individuals each.

Vulnerable The species shows a rapid decline (21-50% in 3 of its generations or in 10 years), and/or the breeding range of the entire species is small (5000-19,999 km2), and/or the available habitat is 500-1999 km2, and/or the population of the entire species is either very small (250-2499 individuals) but stable or small (2500-10,000 individuals) but known to be declining, and/or the range is heavily fragmented with virtual absence of gene-flow between the 6-10 populations left and all subpopulations are below 1000 individuals each

Data-Deficient Suspected to be threatened (thus, in the categories Critically Endangered, Endangered, or Vulnerable as defined above), e.g., the species shows strong declines on at least a local scale, and/or the breeding range is estimated to be less than 20,000 m2, and/or the habitat is assumed to have decreased strongly to less than 2000 km2, and/or the population of the entire species is thought to be below 2500 individuals, but no exact data on the species could be obtained.

Near-Threatened Declining, but with less than 20% in 3 of its generations or in 10 years, and/or the total breeding range has markedly contracted but is still over 20,000 km2, and/or the habitat is known to have decreased strongly but is assumed to be still over 2000 km2, and/or the population of the entire species is either small (2500-10,000 individuals) but stable, or the population is large (over 10,000 individuals) but known to be declining, and/or the range is heavily fragmented with virtual absence of gene-flow between the populations left but at least some subpopulations are still over 1000 individuals.

Conservation-Dependent The species has strongly declined in the past, but is considered to be at low risk at present because virtually the entire population(s) are living in well-managed reserves. The more or less stable numbers and the area inhabited are sufficiently large to avoid inclusion in any of the Threat categories. However, political unrest or economic pressure in the country in which the reserve(s) lay may alter the protection regime, leading to sudden marked declines.

In all the threat categories, the decline is not only the one observed or estimated, but also the one expected in the near future based on knowledge about expected habitat destruction, expected effects of introduced predators, competitors, or diseases, etc.