Bolivar Wastewater Treatment Plant provides an important habitat for South Australian ducks and waders

Abstract. The populations of South Australian duck and wader species have recently decreased considerably, but their abundance at Bolivar Wastewater Treatment Plant in metropolitan Adelaide is poorly known. To help assess the importance of this site for ducks and waders, we made 25 trips to Bolivar between December 2018 and July 2020, during most of which time south eastern Australia was experiencing a long dry period. On each trip, we observed between 11 and 26 species of ducks and waders, with a mean total of 9804 (range 2437–15,653) individuals per trip. At times, we observed several thousand Pink-eared Ducks Malacorhynchus membranaceus, Grey Teal Anas gracilis, and Australian Shelducks Tadorna tadornoides, with occasionally up to 1200 Blue-billed Ducks Oxyura australis and 2000 Hardheads Aythya australis. Several wader species that largely breed in Australia’s semi-arid and arid zones were also observed, including occasionally >1000 Red-necked Avocets Recurvirostra novaehollandiae. Five species of waders that breed in the Northern Hemisphere were also recorded fairly regularly in the summer of both 2018–2019 and 2019–2020, including up to ~2000 Sharp-tailed Sandpipers Calidris
acuminata, 2000 Red-necked Stints C. ruficollis and 150 Curlew Sandpipers C. ferruginea. These observations indicate that this wastewater treatment plant is a critically important refuge site for several species of ducks and waders. Every effort should thus be made to maintain this site for the conservation of these species in the future.