July 21, 2019

High-wire act to save forty-spots

A DAY at the office for Amanda Edworthy involves dangling from pullies and ropes under the spreading canopies of white gums on Bruny Island.

It also involves weighing and taking blood samples from one of the world’s rarest birds, the forty-spotted pardalote – all in the name of ensuring the survival of this little Tassie battler.

In the parlance of the circus, I’ve dubbed Amanda the magnificent woman on the flying trapeze after being recruited briefly to aid her research.

I’ve was happy to handle pardalotes while she took blood samples and checked them for parasites, but when it came to scaling trees to scout pardalote nests I thought it wise to keep a safe distance.

When Amanda, who hails from Canada, arrived in Tasmania three years ago on her pardalote project as part of PhD studies with the Australian National University, the forty-spot looked in dire straits.

Numbers of the tiny birds – Australia’s second smallest at just nine centimetres in length – had plummeted by 60 per cent to just 1500 birds from population counts a decade earlier. No one knew why, and Amanda was charged with finding out.

Three years on her mission has been largely accomplished: she has not only established the reasons for the pardalote demise but her ground-breaking research has enabled a strategy to be drawn up to ensure the birds continue into the future.

It was thought the clearing of favoured white gum habit and die-back during drought in recent years was responsible for the fall in pardalote numbers. Amanda soon discovered this was only partly true. Although a lack of suitable nesting cavities in young trees which replaced old growth which had been logged, and the affects of drought, may have played a part, the population crash was combined with two other issues facing the birds: competition for remaining cavities in trees from a related species, the striated pardalote, and death at the hands of parasitic insects.

Looking closely at nests after scaling the white gums, Amanda and her assistants were shocked to discover parasitic maggots from an endemic fly species living under the skin of fledglings, feeding on their blood. These were killing about 70 per cent of nestlings.

Amanda immediately set about trialling an insecticide which would kill the flies and maggots and not harm the birds. After achieving success with this, she then studied the results of a previous program to erect nest boxes, and decided to expand on this.

With the help of the Bruny Island Environmental Network and the island’s Men’s Shed, 200 nest boxes were constructed and these were placed throughout nesting areas on Bruny and on the Tinderbox peninsula in Kingston, two of the last strongholds of the pardalote.

Amanda has discovered the pardalotes, after avoiding the boxes at first, have now taken up their new homes. The boxes are designed and constructed in such a way – with narrow entrances to deter other nesting birds and mammal predators like possums – to provide ideal homes for the pardalotes. Their construction, incorporating a removable top, also enables them to be easily fumigated against the fly menace.

Along with the program to provide the pardalotes with new homes, covenants have been placed on some of the existing privately-owned white gum woodlands on Bruny to guarantee they are not logged in future.

The pardalotes might have been the central focus of the research project but there is a valuable spin-off for the Bruny Island community, and that is tourism. The forty-spot is one of 12 Tasmanian endemic bird species, all found on Bruny Island, and each year these attract birders from all over the world, as part of package bird tours to Australia.

The Bruny community has banded together to save the 40-spot, and in the years ahead the pardalote will no doubt return the favour.

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