This Important Bird Area (IBA) consists of Lake Nabugabo (3,500 ha), a shallow freshwater lake of 8 km by 5 km, and extensive swamps and small forests to the north, east and south, where Sango Bay adjoins. Three much smaller satellite lakes, Birinzi (formerly Kayanja), Manywa and Kayugi are located to the north-west at a slightly higher altitude. Nabugabo is separated from Lake Victoria by an arm of the Lwamunda swamp and a sandbar. Large plants such as Loudetia dominate, but Miscanthus and Vossia, as well as Sphagnum bogs, are also present. Papyrus occurs, but does not dominate any part of the swamp. There is a belt of depleted tropical forest along much of the western shore, and sandy shores along the windward, north-western shoreline. Similar forests exist along the eastern sandbank, some of which are gazetted Forest Reserves. The lakes have been isolated from Lake Victoria for about 3,700 years, during which time the cichlid fauna has undergone speciation. Lake Nabugabo is a popular resort, especially at weekends and public holidays.
Over bird 180 species have been recorded and the scarce Serinus koliensisis among the species of the Lake Victoria Basin biome that are present. Two additional species of global conservation concern, Gallinago media and Circus macrourus, were recorded in December 2000 on seasonally flooded grassland. Hylia prasina and Alcedo quadribrachys occur in the forested areas close to the lake.
Nine species of indigenous fish of the family Cichlidae have been recorded from the lakes, including five endemic species of Haplochromis. The introduction of the non-native fish Oreochromis niloticus, O. leucosticus and Tilapia zillii in the 1950s and Lates niloticus in the early 1960s in both Lakes Victoria and Nabugabo has impacted negatively on the indigenous fish, which may now only remain in the satellite lakes.