Fossil shorebirds (Aves: Charadriiformes) reveal trends in Pleistocene wetlands at Naracoorte Caves, South Australia

Abstract

Charadriiforms (shorebirds and kin) are widespread birds (Order Charadriiformes), whose dependence on coastal and wetland environments makes them effective palaeoenvironmental indicators. Wading charadriiforms are rare in the fossil record, but Pleistocene deposits from the Naracoorte Caves World Heritage Area, South Australia, have yielded an unusually high abundance of charadriiform remains. This study used the fossil charadriiforms from a Late Pleistocene fossil assemblage in Blanche Cave, Naracoorte, to provide new data on the palaeoecology of the region. A total of 288 charadriiform specimens excavated from the upper metre of the Third Chamber in Blanche Cave (~60 to 14 ka) includes nine species, representing at least four families: Charadriidae (Plovers), Pedionomidae (Plains-wanderer), Scolopacidae (Sandpipers and Snipes), and Turnicidae (Buttonquails). Most charadriiform species identified from the assemblage were wading shorebirds, but the most abundant species were terrestrial. The palaeoenvironment around Blanche Cave during the period of fossil deposition is best interpreted as a mosaic vegetation dominated by open forest and woodland, but the presence of wading species indicates that wetlands were also a major and regular component of the environment—likely occupying flat, low-lying areas near the caves. A decrease in the abundance of wading species at the end of the Last Glacial Maximum (~17 ka) and a concomitant increase in the abundance of buttonquails also indicates that warming climates at this time were accompanied by a pronounced decrease in available wetlands. This highlights the unique palaeoecological data offered by shorebirds, affirming the need to consider fossil birds in faunal analyses.