A new generation of 40-spotted pardalotes has been roaming the white gum woodlands of Bruny Island scouting nesting sites for the breeding season.
The young pardalotes are the product of an ambitious program last year to supply 200 nest boxes to help halt the staggering decline in the numbers of these tiny birds, which are only found in Tasmania.
The program is being run over four years by bird researcher Amanda Edworthy, with the aim of not only giving the pardalotes nesting sites to overcome a shortage of suitable tree hollows for these cavity-nesting birds, but to allow them to be closely monitored so the reasons for the decline can be better understood.
Numbers of forty-spotted pardalotes have been in freefall in recent years, dropping by about 60 per cent, and the total population now stands at between 1200 and 1500 birds.
A lack of nesting hollows in white gums – the trees suffering dieback in recent years because of drought – had been thought previously to be the main reason for the pardalote population collapse but Edworthy is already discovering other problems facing the birds.
Bird lovers were last year invited to sponsor individual boxes and I signed up for one that was high in a eucalypt on the slopes of Waterview Hill on North Bruny Island.
In fact pardalotes failed to show any interest in my first box so Amanda quickly assigned me another one, Box Number 10, that was occupied.
Box 10 and its occupants gave Edworthy plenty of information for her research during the course of the breeding season. Her record cards show that the box was occupied right at the start of the spring breeding season. The pardalote pair managed to raise two young before the nest was taken over by striated pardalotes in early October.
Warning signs were there when Edworthy observed 40-spots chasing off the larger striated pardalotes on October 1. The 40-spots valiantly defended their precious nest site for about 20 minutes, before the bigger pardalotes retreated. But there was no doubt they would be back, because in that location there were not many nesting cavities.
When Edworthy revisited the nest on October 8 it was clear the striated pardalotes had managed to evict the 40-spots and were already lining the box with their own nesting material.
The striated pardalotes managed to incubate four eggs and the young were well on the way to developing when they were afflicted by screw-worm fly parasites.
Flies had laid their eggs on the young, so they could feed on their blood. It is a common problem Edworthy has discovered in both nests of 40-spots and striated pardalotes.
The maggots cause anaemia in the nestlings, often but not always killing them. Survivors carry scars from where the maggots have been attached to them.
In the case of the striated pardalotes, only one young survived.
During the course of last season’s survey each 40-spot pair using the nest boxes produced an average of one nestling. Forty-spotted pardalotes may live to be 12 to 15 years old, and so could produce up to 15 offspring at this rate.
Forty-spotted pardalotes use tree holes with small entrances and deep chambers in their favoured white gums to protect them from predators and bad weather. Ancient, dying trees produce the most tree hollows, however in eastern and south-eastern Tasmania almost all white gum woodland habitat is second-growth forest, which lacks these old trees.
There is no doubt the nest box program – the boxes are produced by members of the Bruny Men’s Shed and cost $25 each to sponsor – have given the pardalotes a breeding boost on Bruny and Maria islands and at another 40-spot stronghold, the Tinderbox Peninsula.
The 40-spots – Australia’s second smallest bird – need all the help we can give them.