'Endangered' in relation to a particular migratory species means that the migratory species is in danger of extinction throughout all or a significant portion of its range (Source: CMS Art. 1e) and clarified in Res. 5.3. as meaning “facing a very high risk of extinction in the wild in the near future” (in order to achieve maximum compability with IUCN Categories of threat)

A taxon is Critically Endangered when the best available evidence indicates that it meets any of the criteria [A to E] for Critically Endangered, and it is therefore considered to be facing an extremely high risk of extinction in the wild. A taxon is Endangered when the best available evidence indicates that it meets any of the criteria [A to E] for Endangered, and it is therefore considered to be facing a very high risk of extinction in the wild.(Source: IUCN RED LIST criteria, 2001)

Animals, birds, fish, plants or other living organisms threatened with extinction by natural or human-induced changes in their environment. (Source: GEMET/TOE/KOREN) [...] unless steps are taken to change the cause of threat and decline. (Source: GEMET/BRACK)