The discovery of fossilized shorebirds offers a fascinating glimpse into Australia’s climatic history. These birds, which thrive in coastal and wetland areas, serve as reliable indicators of past environmental conditions. Although it is uncommon to find wading shorebirds in the fossil record, the Pleistocene layers from the Naracoorte Caves World Heritage Area in South Australia have surprisingly revealed a wealth of these remains. Recent studies focused on these fossils have unveiled how wetlands once flourished in the region before disappearing due to climate changes that occurred up to 60,000 years ago. Researchers suggest that a significant drying period, starting around 17,000 years ago, likely contributed to the decline of many of the nine or more fossil shorebird species identified in one of the Naracoorte Caves.
For context, the red knot (Calidris canutus), a juvenile bird photographed near Gourinet, Brittany, France, illustrates the kind of shorebirds studied. Flinders University Ph.D. candidate Karl Lenser expressed surprise at the sheer number of shorebird fossils found in Blanche Cave, stating, "Shorebirds are rare in the fossil record, so finding so many in one cave was unexpected. This indicates that during the last Ice Age, wetlands and mudflats—essential feeding grounds for species like plovers, sandpipers, and snipes—were much more prevalent in the area."
Today, however, climate change and habitat loss are severely impacting existing shorebird populations across Australia. Understanding how these birds adapted to past climate shifts might be essential for predicting their responses to future environmental challenges.
Among the findings, researchers were particularly intrigued by the remains of a specific bird—the plains-wanderer. This small, endangered bird primarily inhabits limited populations in Victoria and New South Wales, yet it turned out to be one of the most frequently discovered species in this study. More than half of the nearly 300 bones examined belonged to plains-wanderers. Lenser noted, "Currently, living plains-wanderers are very selective about their habitats, but fossils from Naracoorte indicate that the area was likely a woodland environment—quite different from the open grasslands that these birds occupy today."
Naracoorte stands out as the only fossil site in Australia where plains-wanderers are found in such abundance. This suggests that events over the last 14,000 years have caused a dramatic reduction in their population sizes, confining them to a much narrower range of habitats devoid of trees, unlike the woodlands they occupied for the previous hundred thousand years.
Additionally, this collection of shorebirds is remarkable because it documents migratory species that travel annually from the northern hemisphere to spend the boreal winter in Australia. According to Dr. Trevor Worthy from Flinders University, this includes three species of sandpipers from the genus Calidris as well as Latham’s snipe (Gallinago hardwickii). He further noted, "The double-banded plover, which migrates between Australia and New Zealand to breed, is also common in this fossil assemblage. Two of the birds were less than a year old, showing they flew the 2,000 kilometers from New Zealand as fledglings only to be captured by an owl near Blanche Cave at Naracoorte."
While there is still much to learn about the bird populations in Australia during the last Ice Age, fossils from sites like Naracoorte are crucial for bridging the knowledge gap. Lenser added, "The Naracoorte Caves preserve an incredible half-million-year record of biodiversity in southeastern South Australia. This study clearly shows that the caves offer insights into landscapes prior to European settlement, providing key information relevant to the conservation of threatened species today."
Visitors to the Naracoorte Caves can witness ongoing excavations and delve deeper into the science behind Australia’s only World Heritage Area.
The comprehensive findings from this research were published in the journal Palaeontologia Electronica.
