A striated pardalote in a nesting hollow. Abundant and aggressive species such as starlings and cockatoos are often first to occupy hollows.

New research suggests that land-use changes in Tasmania’s Midlands are increasing numbers of larger birds such as cockatoos and ravens.

Birds that forage among treetops and midstory vegetation may have declined, including species unique to Tasmania.

Surveys were conducted in woodlands of the Midlands Biodiversity Hotspot, the focus of an ambitious ecological restoration program and Australia’s second oldest agricultural landscape.

Bird data were related to land-use change over the last twenty years to explore the current state of local bird communities and how they might have changed.

Beyond the direct clearing and fragmentation of habitat that typically accompanies agriculture, farm management practices can modify wildlife communities through their effects on the abundance of food, shelter and predators.

Analysis of change suggests increases in large-bodied granivorous or carnivorous birds and declines in some arboreal foragers and nectarivores. Changes in species richness were best explained by changes in noisy miner abundance and levels of surrounding woodland cover.

According to ecology researcher Dr Glen Bain of the University of Tasmania, the booming population of starlings and cockatoos may put pressure on dwindling numbers of tree hollows as many of the old dead trees are being removed. Suitable hollows, he noted, often took over a hundred years to form.

“It may be worth us thinking about erecting nest boxes in what little ‘good quality’ habitat remains; plantings do not make up for losing old remnant habitat elsewhere,” he told Tasmanian Times. Currently there are no programs to install such nest boxes.

Noisy miner (Manorina melanocephala).

“If we put next boxes in large patches of good vegetation I’m sure we’d get species using them, the problem however is that there is so little native vegetation left in the area.”

Bain said they had been surveying ‘everything from bats to quolls’ to accumulate baseline data as well as his own specialty, birds. Surveys were conducted at 76 locations on private properties throughout the midlands.

Bird observations were compared to some historical data from 1990s, and related it to things like the way farmers were using their land.

“A major driver of what’s going on in the Midlands is the presence of this aggressive species called the noisy miner,” he said. Consideration had to be given to how to prevent them overtaking the space of smaller, vulnerable species such as songbirds, he suggested.

“Currently there are lots of people all over the country working on a solution to the noisy miner problem. I’ve suggested that as noisy miners don’t like dense vegetation, if we just plant eucalypts we are providing more habitat for them.” Gorse, being dense, could be replaced gradually as it is useful habitat for birds, quolls and devils.

Fieldwork among the gorse.

Sulphur-crested cockatoos have benefited from the amount of cropping in the Midlands.

Dr Bain stressed that more studies are crucial to sustaining our bird populations. “What I’m pushing through my research is considering the common species or what we call common now before they end up becoming endangered ones and it’s too late. No ones really been monitoring bird species in Tassie so we don’t really know what’s going on with them.”

The research paper Changing bird communities of an agricultural landscape: declines in arboreal foragers, increases in large species was published by The Royal Society in March.

Midlands landscape. All images in this article courtesy Dr Glen Bain.

Source: Tasmanian Times https://tasmaniantimes.com/2020/04/midlands-land-use-changes-favour-larger-birds/#utm_source=rss&utm_medium=rss&utm_campaign=midlands-land-use-changes-favour-larger-birds

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