One of Australia's most endangered birds facing threat from maggots

Updated

Researchers are trialling a novel method of controlling the fly larvae in a bid to save the extremely rare 40-spotted pardalote.

In the last 20 years they've declined by about 60 per cent and nobody knew exactly why. ANU PhD student Amanda Edworthy

A three-year study of the endangered 40-spotted pardalote has "surprisingly" found tiny parasitic larvae have driven population numbers to the brink.

Amanda Edworthy, a PhD student from the Australian National University, has been researching the pardalote in southern Tasmania, the only place in the world where it can still be found.

Her study's objective was clear.

"In the last 20 years they've declined by about 60 per cent and nobody knew exactly why, so the goal of my project was to figure out what was wrong with their population," she said.

At this point in time we're probably hovering around [a total population of] 1,000 birds. Zoologist Dr Sally Bryant

Zoologist Dr Sally Bryant said there had been a dramatic population drop.

"The early surveys of the species from the 80s and 90s had populations of nearly 4,000," she said.

"At this point in time we're probably hovering around 1,000 birds. This little species is uniquely Tasmanian; it actually belongs on this island, it's part of our ecosystem.

"If we can't look after it here then we are going to lose it forever."

Ms Edworthy's study into what caused that drop has had an unexpected finding.

"The main thing that we found was these parasitic flies infecting the nestlings," she said.

"So the adults lay their maggot larvae inside the nest and the larvae burrow underneath the skin of the nestlings where they feed on their blood and cause about 75 per cent mortality, so that's huge for a songbird.

"This is a big surprise."

The cotton wool method involves spraying little balls of cotton with a plant-based insecticide that kills larvae of a parasitic fly but does not harm birds. Flinders University professor of Animal Behaviour Sonia Kleindorfer

To stop the fly larvae, Ms Edworthy's been climbing up trees and spraying individual nests with a mild insecticide.

She said it was an effective, but impractical method.

"With the fly spray we were able to kill off almost all the parasites, and that led to a fledge rate of 90 per cent, so 90 per cent were actually surviving," she said.

A team from the University of Utah had a similar problem with Darwin's finches on the Galapagos Islands.

Sonia Kleindorfer, from Flinders University in Adelaide, has written about the cotton wool method used to help.

"The cotton wool method involves spraying little balls of cotton with a plant-based insecticide that kills larvae of a parasitic fly, but does not harm birds," she said.

The researchers leave specially designed stations with the cotton wool intertwined with wire in the bush.

The 40-spotted pardalote comes to the station, and tears off small pieces of wool to weave into its nest.

I think it could be really important for just helping these birds to just hang on in the short-term. ANU PhD student Amanda Edworthy

Ms Edworthy said it was a method that would be trialled in Tasmania in the next two years.

She said she was hopeful it would save the species.

"I think it could be really important for just helping these birds to just hang on in the short-term," she said.

"Over the long-term I think it's really important to figure out why parasite loads have increased so much, or if they have increased, why?

"And then figuring out ways to manage forests to help reduce fly populations in general."

Topics: endangered-and-protected-species, environment, animal-science, science-and-technology, animals, tas

First posted