Wetlands around the Goulburn Broken Catchment are being listened to, to see how they respond to environmental water allocations.
Five wetlands – Kinnairds, Reedy, Black, Doctors and Moodie - currently receive environmental water to maintain or promote plant growth and encourage bird breeding.
When water is delivered to a wetland Goulburn Broken Catchment Management Authority (CMA) Environmental Water Project Officer Jo Wood heads out with her acoustic recorders to see how the wetlands respond.
She puts the recorders out for a 48-hour period. They record every 30 seconds at 30 minute intervals. The recorders are then brought back to the office and listened to and “looked” at.
“Each animal has its own individual call which show up as a picture. Each picture is a bit like a fingerprint and you can recognise species from the picture of the call,” Ms Wood said. “The response after water is delivered is nearly instant. Frogs start calling and some waterbirds such as ducks and swans have been recorded calling within the first 24 hours of delivery.
“Earlier this year we found Magpie Geese at Kinnairds Wetland in Numurkah. The wetland was drawing down after an environmental water allocation and I thought it would be a good idea to get one more recording before it dried completely. We recorded Magpie Geese and also sighted them, which allowed us to transfer some more environmental water to the wetland to help the geese with feeding and roosting over the warmer months. If we hadn’t put the recorders out we would never have realised they were there.”
Using acoustic recorders to monitor these wetlands also provides insight in to what moves in and out of the wetlands on a daily basis. Earlier this year recordings at Black Swamp near Wunghnu indicated Plumed Whistling Ducks were moving into the wetland around 9pm and leaving at 5am.
“We don’t have the (people) capacity to monitor these swamps for 24 hours a day, that’s another reason why we use the recorders,” Ms Wood said. “We would never have known the Plumed Whistling Ducks were using the swamp as a roosting site if it wasn’t for the recorders.”
Ms Wood also discovered that one species of frog at Black Swamp would stop calling when cars or trucks went past on the highway over 2km away.
“The Banjo Frogs would call at night but when a truck or car went past that was at the same frequency as the frogs, the frogs would stop calling.
“It was like it was competition for the frogs. As soon as the traffic passed, they would start calling again. This type of thing has been seen in the US at an Army Base where there is a flight training path flying over a lake. Every time the planes would fly over the frogs would stop calling. This then made them susceptible to predators because as they would start calling the predator could hone in on where they were calling from and pick them off.”
Ms Wood recently attended the Ecoacoustics Congress in Michigan US, where she presented her findings of wetland response to environmental water.
A branch of the International Society of Ecoacoustics called the Australasian Chapter of Ecoacoustics was recently developed, with Ms Wood nominated as its inaugural president.
“We already have 50 members and we only began in July 2016. Ecoacoustics is fast becoming an important way to monitor the environment and it’s amazing the work that is being done in Australia. Using these techniques has given me such a great working knowledge of our wetlands and their response to environmental water. Looking back I don’t know what we did without them (acoustic recorders).”
Recordings of some birds and frogs can be found on the Goulburn Broken CMA’s Sound Cloud channel.