A bird species common in northern NSW but rarely sighted in Victoria has found a home near a Melbourne sewage plant.
Tawny Grassbirds are found scattered mostly in coastal northern Australia and are rarely seen in groups of more than two.
But birdwatchers have uncovered five at Yarra Valley Water's Lilydale Sewage Treatment Plant.
"Tawny Grassbirds are a very rare species in Victoria, with just a handful of records to date," said Monash University's Rohan Clarke, who confirmed the sighting.
"The five Tawny Grassbirds found at Lilydale treatment plant over summer is the largest group ever observed in the state."
The birds were exhibiting breeding behaviours and Dr Clarke said recent sightings could lead to a permanent Victorian population.
"Sewage treatment plants provide important refuges for wetland species, attracting water birds to the treatment ponds and various reed-loving songbirds to the wetland fringes," Dr Clarke said.
Yarra Valley Water's biodiversity officer Chris Farrow said it was too early to know why the birds had migrated so far south, but the sewage treatment plant site was a perfect breeding ground.
"If it's getting too hot in other areas, or if grasslands in their previous habitat are being destroyed, then sites like this become very attractive for species like the Tawny Grassbirds," Mr Farrow said.
Yarra Valley Water will protect the area during the breeding and hatching period and minimise human interference.
"Once the mating season ends, we can go in and have a closer look and see what else we can do to help this little colony thrive," Mr Farrow said.
"Ultimately, our goal is to enhance the site for conservation and make sure they don't need to migrate elsewhere."
The Tawny Grassbird's breeding season tends to finish by April or May.
