Paraguay ratified CMS on 23 October 1998 and became its 56th Party with effect from 1 January 1999. The country had long ago shown interest in the Convention, which it had signed already in 1979, but the necessary ratification had not been possible until now. Paraguay is strategically situated in the centre of the South American flyway for migratory birds. It also shares important ecosystems (tropical forest, wetlands) with its neighbouring countries. Among the country's most outstanding wild animals are several species of migratory fish, particularly in the basins of the rivers Paraguay and Paraná.

Slovenia joined CMS with effect from 1 February 1999 (thus becoming its 57th Party). This mountainous country also has important wetlands, which waterbirds use for breeding, for wintering and on passage. These include species such as storks, herons, waders, terns and warblers. Slovenia also holds important populations of bats and of birds of prey. It is a Range State for several Appendix I species, among which are the Great Bustard (Middle-European population) and the Slender-billed Curlew. Being riverine to the Adriatic Sea, it is also a Range State for ACCOBAMS.