The bones of Dromornis stirtoni, possibly the largest bird that ever lived, revealed the fatal weakness that wiped out its offspring 7 million years later. Apparently the birds were taking too long to reproduce.
Australia was once home to birds up to four times the size of ostriches, the largest birds today.
Of these, probably the biggest was Dromornis stirtoni. These were Dromornithidaerelatives of modern chickens and ducks, which grew up to 3 meters tall and weighed up to 500 kilograms.
Birds have not adapted well enough to climate change
A study published in Anatomical Record compare the growth patterns recorded in bones D. stirtoni and Genyornis newtonithe last of Dromornithidae, which became extinct only 50,000 years ago.
Although D. stirtoni grew extremely rapidly in the first two years of life, their growth slowed down thereafter and the birds reached breeding size much later. Genyornis it reached maximum size earlier, but still inherited the late reproduction of its giant ancestor, leaving it without the ability to cope as a species in the long term.
“About 8 million years ago, Australia had a very different climate, with rainforests in the heart of the continent,” said Dr Trevor Worthy of Flinders University.
These forests supported three species of Dromornithidaeincluding the largest, D. stirtoni.
As the rainforest dried up, D. stritoni and two other smaller species of Dromornithidae disappeared, but their descendants, incl Genyornishave continued to play an important role in Australia’s ecosystem.
Slow reproduction, specific to stable environments
“In fact, they have persisted through several major environmental and climatic perturbations,” Worthy said, quoted by IFLScience.
“However, while Genyornis it was better adapted than its ancestors and survived for two million years of the Pleistocene, when arid and drought conditions were the order of the day, it was still a slow-growing and slow-breeding bird compared to the emus.”
emu birds (Dromaius novaehollandiae) reach the reproductive stage at the age of two.
Such slow reproduction is common for species that live in relatively stable environments such as tropical forests – where all species of Dromornithidae.
Worthy also compared these birds and with kākāpō (Strigops habroptilus), from New Zealand, which can live for almost a century, but reproduces only once every five years.