A cheeky, cheese-loving bird that lives on a tiny island off the southern Great Barrier Reef is giving researchers a rare insight into the real-time workings of evolution.
Described by researchers as an “island ark”, Lady Elliot Island continues to yield insights into the resilience and wonder of the natural world.
Lady Elliot Island is the southern-most island in the Great Barrier Reef. (Supplied: Lady Elliot Island Eco Resort)
Turned into a barren wasteland by 19th century guano mining and decades of mismanagement, a dedicated revegetation project which began in the 1960s has restored the forest ecosystem.
The island is now home to 95 different bird species, the second highest diversity of birds on the Great Barrier Reef.
Lady Elliot Island was reduced to a barren wasteland through guano mining and goat grazing for stranded sailors. (Supplied: Lady Elliot Island)
One of the most common of those birds is the silvereye — a busy, colourful bird named after a distinctive ring of white feathers around its eye, well known to migrate along great swathes of the Australian coastline.
But a new study by the University of the Sunshine Coast, published in Nature Scientific Reports, has found the Lady Elliot Island silvereye population has not only settled on the island paradise but has already begun to evolve away from its mainland cousins.
The Lady Elliot Island silvereye population has begun to evolve away from its mainland cousins. (Supplied: University of Sunshine Coast)
Evolution in action
The research team took blood samples from silvereye populations on Lady Elliot Island, Heron Island and mainland groups on the Fraser Coast and Sunshine Coast.
Genetic analysis of the samples showed the Lady Elliot Island silvereyes had diverged into a unique subspecies in just a few decades.
University of Sunshine Coast study co-author Annika Radu holds a silvereye on Lady Elliot island. (Supplied: University of Sunshine Coast)
Animal ecologist Dominique Potvin said the findings were remarkable and a rare view of evolution in action.
“What is really cool about this study is you could almost see the first step of that [adaptation] process happening here,” she said.
“We could almost predict that in a few hundred or a few thousand years, these different populations might actually become their own species.”
The Lady Elliot Island birds are larger than mainland silvereyes, which Dr Potvin said was typical of island evolution due to fewer predators and less competition from rival species.
They have a brighter yellow and white plumage.
Lady Elliot Island silvereyes are larger in size and have brighter plumage. (Supplied: University of Sunshine Coast)
Dr Potvin said the natural bounty and seclusion of its new-found home seemed to have accelerated the island birds’ genetic divergence, to the point that they now reject attempts by mainland silvereyes to join the colony.
“There’s something about being isolated on an island that is … really awesome, and having that water barrier … means they’re not accepting outsiders,” she said.
The findings are testament to the benefits of the revegetation project, Dr Potvin said.
“The birds that you see here are very similar to ones that you see on islands that have been intact for thousands and thousands of years,” she said.
“It really means that it is working and it’s a success.”
Island refuge
The silvereye study was part of a broader Leaf to Reef project documenting biodiversity on the island.
Lady Elliot Island is a 20 minute flight from Bundaberg in Central Queensland. (Supplied: Lady Elliot Island)
Researchers anticipate Lady Elliot Island will become a refuge for species migrating southwards due to the impact of climate change on the Great Barrier Reef.
Peter Gash is the current custodian of the island and his business, Lady Elliot Island Eco Resort, is a partner in the Leaf to Reef initiative.
He takes heart from the silvereye study, seeing their success as the culmination of his decision to plant low bushes favoured by the birds once he saw them starting to return to the island.
Peter Gash has been the island custodian since 2005. (ABC Wide Bay: Brad Marsellos)
Mr Gash said the “pretty, petite” silvereyes were frequent visitors to his breakfast table, showing a quirky proclivity for dairy products.
“They’ll just hop around on the table and steal the cheese or your milk, and they look at you as if to say, ‘No worries, you don’t mind?'” he said.
“It’s hard to put words to that experience, it’s just nature at its finest.”
Mr Gash said research on the island he described as the “Australian Galapágos” was yielding insights of far-reaching significance for our role as nature’s custodians for future generations.
“We’ve got a brilliant teacher in the form of science that teaches us what does work and what doesn’t work,” he said.
“We all have a circle of influence, we all have a certain circle of reach.
“We owe it to the future, we owe it to our youth that we’re going to do our best.”
