Shorebirds are widespread birds whose dependence on coastal and wetland environments makes them effective paleoenvironmental indicators. Wading shorebirds 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 shorebird remains. A new analysis of Naracoorte Cave fossils reveals how wetlands once thrived and then vanished as the climate warmed up to 60,000 years ago. The study authors link a phase of pronounced drying from about 17,000 years ago as being the likely cause for the decline of many of the nine or more fossil shorebird species found in just one of the Naracoorte Caves.
The red knot (Calidris canutus), juvenile, near Gourinet, Brittany, France. Image credit: Stephan Sprinz / CC BY 4.0.
“Shorebirds are rare in the fossil record, so finding so many in one cave (Blanche Cave) was a surprise,” said Flinders University Ph.D. candidate Karl Lenser.
“This shows that the wetlands and mudflats, where birds like plovers, sandpipers and snipes feed, were much more common in the region during the last Ice Age.”
Climate change and shrinking habitat are causing living shorebird populations in Australia to fall.
Understanding how these species responded to past climate change may be key to predicting how populations will be affected in the future.
Lenser and his colleagues were particularly puzzled by the fossils of one bird.
The plains-wanderer — a small, endangered bird which is found predominantly in small populations in Victoria and New South Wales — was one of the most common species identified in the study.
Over half of the nearly 300 bones examined by the authors were identified as plains-wanderers.
“Living plains-wanderers are now very selective about their habitat, but other fossils from Naracoorte show that the area was probably a woodland … a far cry from the treeless open grasslands plains-wanderers inhabit today,” Lenser said.
Naracoorte is the only fossil site in Australia where plains-wanderers are found in such high numbers, suggesting that events in the last 14,000 years caused a large decline in populations of this intriguing bird.
This decline was associated with the plains-wanderer becoming limited to a narrower range of habitats where trees are absent, rather different to the woodlands it occupied during the last hundred thousand years.
“This sample of shorebirds is also extra special as it documents migratory species that annually fly from the northern hemisphere to spend the boreal winter in Australia,” said Flinders University’s Dr. Trevor Worthy.
“These include three species of sandpipers in the genus Calidris and the Latham’s snipe (Gallinago hardwickii).”
“Also common in the fossil assemblage is the double-banded plover which migrates from Australia to New Zealand to breed.”
“Two birds were less than a year old indicating that they had flown as fledglings the 2,000 km distance from New Zealand only to be captured by an owl near Blanche Cave at Naracoorte,” Dr. Worthy said.
“There is still a lot we don’t know about birds in Australia during the last Ice Age, but fossils from caves like those at Naracoorte are helping to fill this gap,” Lenser added.
“The Naracoorte Caves preserves a half million-year record of biodiversity in southeast South Australia,” said Adelaide University’s Dr. Liz Reed.
“As this study clearly demonstrates, the caves provide a window into pre-European landscapes and yield information relevant to the conservation of threatened species today.”
“Visitors to Naracoorte Caves can view the excavations and learn more about the science of South Australia’s only World Heritage Area.”
The findings were published online in the journal Palaeontologia Electronica.
_____
Karl M. Lenser et al. 2026. Fossil shorebirds (Aves: Charadriiformes) reveal trends in Pleistocene wetlands at Naracoorte Caves, South Australia. Palaeontologia Electronica 29 (1): a2; doi: 10.26879/1608
