The extinction of the last of Australia's massive thunder birds, Genyornis newtoni, may have been discovered by researchers.
The clue came when a fossil was found. The 160 sq km beds of Lake Callabonna are home to bone infections in several dromornithid remains.
The giant birds were worried about getting stuck in the mud of the lake, but they were also worried about the other issues.
Some of them had a painful disease that would have hampered their mobility.
The candidate said that the fossils were associated with the chest, legs and feet of four individuals. It would have been difficult to find water and food because they were weakened.
It is rare to find fossils with signs of an illness in the fossil record. We have a better idea of the life challenges of these birds.
The study found that about a quarter of the birds were sick.
McInerney said that they see frothy and woven bone, large abnormal growths and cavities in their fossil remains.
A somewhat complex situation may have caused the phenomenon if multiple individuals are found with osteomyelitis.
The study co-author associate professor Lee Arnold dated the salt lake sediments in which Genyornis was found, and they showed that there was a period of severe dry spell beginning about 48,000 years ago.
The thunder birds and other megafauna were facing major environmental challenges at the time.
As the continent dried, large inland lakes and forests disappeared and central Australia became flat desert.
Associate professor Trevor Worthy believes that with the conditions worsening, food resources would have been reduced and the animals would have been stressed.
He said that challenging environmental conditions can have negative effects on birds. The Lake Callabonna population would have been struggling through those conditions.
It now appears that the effects of severe drought phases included high rates of bone infections, with weakened individuals more likely to die in the deep mud.
It is not known if Genyornis newtoni survived past this time, but it is likely due to high disease rates and long periods of dry weather.
Papers in Palaeontology contains the research findings.
