Situated close to Port-Gentil on Cape Lopez, the westernmost part of Gabon, the site comprises much of Mandji island, in the delta of the Ogooué river. The area is mix of sand-dunes, coastal grasslands, swamps, small patches of littoral forests and Dalbergia ecastaphyllum thickets and mangroves. The southern half of Mandji island comprises extensive short-grass savannas on sandy soil, with herbaceous swamps, and areas of littoral forests characterized by Chrysobalanus icaco. Patches of dry forest occur, in which typical tree species include Sacoglottis gabonensis, Pachypodanthium confine and Cola flavovelutina, while Mitragyna ciliata is typical of the swamp-forests. Mangroves are extensive along the Ogooué and large areas of mudflat occur in Cape Lopez Bay.
See Box and Tables 2 and 3 for key species. The avifauna of the area is diverse—323 species have been recorded, but the list is undoubtedly incomplete. Six species of global conservation concern have been found, only one of which is resident: Ploceus subpersonatus, also a restricted-range species, is fairly common and breeds in Phoenix reclinata palms. The other five species are non-breeding visitors from the south (Morus capensis, Phoenicopterus minor and Sterna balaenarum) or Palearctic migrants (Gallinago media and Glareola nordmanni). Only Sterna balaenarum is a regular and common non-breeding visitor, from May to November. Counts of this species made off Cape Lopez have recorded over 900 migrating south. The site is also remarkable for the presence of small breeding colonies of two tern species, Sterna caspia and Sterna hirundo, which nest together with a few pairs of Rynchops flavirostris and Sterna albifrons. This population of S. hirundo appears to be resident. The location of Cape Lopez, a finger of land protruding into the Atlantic Ocean, makes it an important area for migrants and explains the relatively large number of rare species that have been recorded. Counts made in 1992 estimated the number of Palearctic waders in the area to be between 4,210 and 5,845.
Non-bird biodiversity: Among mammals, a small population of Loxodonta africana (EN) survives in the southern part of Mandji island, and dolphins, possibly Sousa teuszii (DD), and Megaptera novaeangliae (VU) are regularly seen offshore.
BirdLife International (2019) Important Bird Areas factsheet: Ogooué delta and Mandji island. Downloaded from http://www.birdlife.org on 12/12/2019.