Waterbird populations at the Orange River mouth from 1980–2001: a re-assessment of its Ramsar status

Abstract

The Orange River mouth (ORM), at the end of the longest river in South Africa, is one of few perennial wetlands on the arid south-west African coast. The ORM supports a large number of waterbirds, with a maximum of 20 653-26 653 individuals of 57 species being recorded in December 1985. Because of its importance for waterbirds, the ORM is recognised as a Ramsar site and an Important Bird Area. Since being designated a Ramsar site in 1991, however, the number of waterbirds has decreased (by c. 74% since the first two surveys in 1980 and 1985). During 13 surveys conducted from December 1995 to August 2001 an average of 6 873 (±1 719 SD; n = 6) and 5 547 (±2 039 SD; n = 7) individuals were recorded during summer and winter, respectively. This decrease, in conjunction with the degradation of the c. 300ha saltmarsh resulted in the ORM being placed on the Ramsar Convention's Montreux Record in 1995. The decrease in the number of waterbirds at the ORM is mainly attributable to the absence of large numbers of Cape Cormorants (Phalacrocorax carbo) and non-breeding Common Terns (Sterna hirundo), with no breeding of the former being recorded on islands in the mouth area after 1993. The decrease in numbers of these two species may be attributed to both on- and off-site factors. During a re-evaluation of the revised Ramsar criteria, we found that the site still meets three of the four Ramsar criteria under which it was originally designated in 1991 and five of the eight new criteria. The establishment of a transboundary statutory protected area will allow for the implementation of conservation-directed management measures. We propose various management recommendations to improve the conservation of wetland birds at the ORM.