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Unprecedented bird sighting at Victorian treatment plant prompts fresh conservation efforts

The unprecedented sighting of a colony of Tawny Grassbirds in Melbourne has created new habitat protection opportunities for one Victorian utility, with conservation plans underway to help preserve the birds’ new nesting site.

A group of Tawny Grassbirds have been discovered in the grasslands near Yarra Valley Water’s Lilydale Sewage Treatment Plant, marking one of the first sightings of this species in Victoria.

Tawny Grassbirds are typically found in northern New South Wales and are rarely seen in groups of more than one or two. However, it’s thought that five of these birds have been breeding in the area for the past two months.

Yarra Valley Water Biodiversity Officer Chris Farrow said it was too early to know why the birds have migrated so far south, but the unusual movement of the species has certainly caught the utility’s attention.

“With rising temperatures in the northern states, and the shifting weather patterns, we think the birds are basically climate refugees looking for a more suitable home,” he said.

“It’s incredible to think that a small enclave of them has gathered, migrated and are now showing mating behaviours. They’re quite small, so they can’t fly too far. It’s likely they’ve been moving further south each year until they ended up down here.”

The birds were initially discovered by local birdwatchers, with Associate Professor Rohan Clarke from Monash University’s School of Biological Sciences confirming the presence of at least five Tawny Grassbirds at the site.

“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,” he said.

“Lilydale Sewage Treatment Plant is an excellent example of this, attracting numerous bird species. It even has a viewing platform for birdwatchers.”

Clarke said there have been fewer than 10 records of this species from the Greater Melbourne area, with recent sighting of a group of Tawny Grassbirds unprecedented in Victoria, given that most other recorded sightings are of single birds.

“Tawny Grassbirds are a very rare species in Victoria, with just a handful of records to date. The five Tawny Grassbirds found at Lilydale Sewage Treatment Plant over summer is the largest group ever observed in the state,” he said.

“It’s possible that these recent Tawny Grassbird sightings around Melbourne are part of a range shift where the species will establish a permanent Victorian population.

“The Tawny Grassbirds frequented an area of tall grassland adjacent to the treatment ponds. Because Yarra Valley Water site managers were able to set this aside for the birds, there is an excellent chance the species was able to breed.”

Protecting habitat

Farrow said the Lilydale Sewage Treatment Plant site is perfect for breeding due to the climate, long grass, and proximity to a water source, and so Yarra Valley Water has added the species and its chosen nesting ground as a new focus within its broader conservation efforts.

“Grasslands have a wonderful cooling effect. 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,” he said.

“The birds are insectivores, which means they primarily eat insects. The site has an abundance of food for them and any new hatchlings. Ultimately, our goal is to enhance the site for conservation and make sure they don’t need to migrate elsewhere.

“We’ll continue to care for them during the breeding and hatching period by protecting the area and minimising 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.”

After the sighting was confirmed by Professor Clarke, Yarra Valley Water moved to proactively protect the habitat to allow the birds to nest and hopefully increase this never-before-seen population in Melbourne.

“We’re planning to engage with the citizen science bird watchers to create a more formalised monitoring program. If the Tawny Grassbird is migrating to the area, then who knows what other species will move here in future, too,” he said.

“We have set aside a section of land to protect their habitat. We’re also considering creating an observational hide on the site for birdwatchers, which is about enhancing the capacity for citizen science to happen.

“If the Tawny Grassbirds decide to stay, we’ll look into how we can alter our grounds maintenance to protect these beautiful creatures.”

“We are developing new ways and means to better support biodiversity on our sites. Under our biodiversity plan, we’re actively increasing the area of land that we’re protecting and restoring, and we’ve set targets to reach nearly 47 hectares of our land by 2030.”

Environmental stewardship

Efforts to help the Tawny Grassbird colony are a natural extension of YVW’s strong conservation focus, Farrow said, with the utility committed to changing how it operates to be more beneficial for the environment.

“We’ve got a large catchment throughout Melbourne. Our customers have told us that biodiversity and environmental conservation are really important to them,” he said.

“There is an expectation that we manage the land that we hold and deliver our core business of water provision in an environmentally and nature-positive way. We also have our commitment to caring for Country and working with Traditional Owners.”

Yarra Valley Water’s 2030 Strategy outlines the utility’s robust and proactive approach to biodiversity and land management, with recent projects including creating over 35 hectares of new habitat for the critically endangered Helmeted Honeyeater and lowland Leadbeater’s Possum at the Upper Yarra Sewage Treatment Plant site, with guidance from the Narrap Rangers.

Farrow said another exciting new project currently underway is set to help protect habitat for the Eltham Copper Butterfly, which was thought to be extinct in the 1950s – with a small population rediscovered in the 1980s.

“On another treatment plant we have a couple of populations of the butterfly, which are monitored by the Friends of the Eltham Copper Butterfly citizen science group,” he said.

“The butterflies are a gorgeous copper colour and about the size of a thumbnail. They have an amazing symbiotic relationship with a specific plant, a small shrub called Sweet Bursaria, and a specific species of ant, the Notoncus,” he said.

“These three entities exist and depend on one another. The butterflies lay their eggs on the lower stem of the plants. The ants nest underneath the plant and, when the larvae hatch, the ants shepherd the caterpillars up and down the stem of the plant so they can eat the leaves.

“During the day, the caterpillars excrete a sugary substance from their skin, which the ants eat. Once the butterflies emerge, they then go on to pollinate the plant and lay their eggs on the plant again after breeding season. It’s an amazing cycle of events.

“These butterflies are critically endangered. We have land adjacent to existing habitat. It makes perfect sense for us to focus on helping the species. We have a staff volunteer project to increase the health of the habitat for the species, as well.”