Dr Jim Radford, Bush Heritage Ecological Outcomes Monitoring Coordinator, explains the results of bird monitoring in the South-East Grassy Box Woodland reserves.
Diamond firetail. Photo Wayne Lawler / EcoPix.
During hard times, it’s good to know that there are places where food and shelter are still plentiful.
Areas rich in resources have always been critical in helping species to survive the lean times resulting from drought, fire, flood or other vagaries of nature. But, in the face of rapid climate change, such places are about to become even more important.
By protecting and managing high-quality, highly productive habitats, Bush Heritage is helping to protect these refuge areas and increase the chances of survival for a wide range of native species.
Not all natural areas are equal when it comes to providing habitat for native animals. The quality of habitats varies naturally with the type and condition of native vegetation, the size and distribution of the patches that remain, the abundance of introduced species and native competitors, and the frequency and intensity of disturbances.
The woodland canopy at Tarcutta Hills Reserve, NSW, is home to a number of declining woodland bird species. Photo Wayne Lawler / EcoPix.
Habitat quality also varies over time, with some areas remaining in better condition for longer than others. These areas that remain in good condition through lean times we like to call ‘refuge areas’.
In times of environmental stress, resource-rich refuge areas are magnets for native animals, drawing them in from the surrounding landscape as resources elsewhere become more and more scarce, then providing the springboard from which they can recolonise the landscape when these conditions improve.
As a matter of priority, Bush Heritage actively seeks to protect those parts of the landscape that have the greatest potential as refuges and to manage these areas to increase the availability of essential resources (i.e. food, shelter, mates).
By alleviating external stresses such as clearing, grazing, introduced predators and herbivores, weeds, inappropriate fire regimes and chemical additives, we can encourage the growth of native vegetation and increase the capacity of the ecosystem to withstand or absorb ‘natural’ shocks such as variations in climate.
Fuscous honeyeater. Photo Wayne Lawler / EcoPix.
In so doing we make the landscape more resilient. Although only just beginning to yield results, our Ecological Outcomes Monitoring program can tell us about our progress towards these goals.
In Bush Heritage’s South-East Grassy Box Woodlands anchor region, Tarcutta Hills Reserve in New South Wales and the Nardoo Hills reserves in Victoria protect high-quality, intact remnants of grassy white box Eucalyptus albens woodland and hillcrest herb-rich woodland, respectively.
These reserves also support a high diversity of woodland bird species. Many of these, such as the hooded robin, crested shrike-tit and diamond firetail, are currently in precipitous decline throughout much of southern Australia.
A key conservation goal for both reserves is to protect and ultimately increase their populations. Since 2006, as part of our Ecological Outcomes Monitoring program, we've been systematically surveying the bird communities at both Tarcutta Hills and Nardoo Hills.
Speckled warbler. Photo Wayne Lawler / EcoPix.
Although we have data for only two years, both exceptionally dry years at the end of a decade of low rainfall in south-eastern Australia, we are already starting to see interesting patterns emerge.
Many food sources, especially nectar and seeds, are naturally patchy, with considerable variation in where and when they occur; for example, the same patch may provide food in one year but not the next. This means that the bird species that rely on these resources must be highly mobile to track them across the landscape. Fluctuations in population size can be expected due to variations in the food supply.
This pattern has been evident at Tarcutta Hills. In 2006 there was ample flowering and a lot of seed, whereas in 2007 there was virtually no flowering and much less seed. Consequently, the numbers of seed-eating species, such as the peaceful dove, and nectarfeeders, such as the black-chinned honeyeater and red wattlebird, declined dramatically in 2007.
In contrast, the insect-eating birds at Tarcutta Hills showed a very different response. The overall numbers of all species of insect-eaters that foraged in the tree canopy, on the ground, on bark or in the air, either increased in 2007 or remained stable.
Grassy woodlands provide vital habitat for declining woodland birds at Nardoo Hills Reserve, Vic. Photo David Tatnall.
The number of species of insect-eaters also increased in 2007 as several species typical of the drier country to the west, for example the red-capped robin and western gerygone, moved into the reserve.
That the insect-eating community was able to persist and even grow in 2007, despite several years of low rainfall, suggests that Tarcutta Hills Reserve is retaining its critical resources very well.
The results from Nardoo Hills are even more encouraging. While the nectar-feeders declined slightly, the abundance of all insect-eating groups and seed-eaters increased in 2007.
Insect-eaters are particularly good indicators of ecological health because they're relatively high in the food chain, and many species are year-round residents. Thus, the increase in the numbers of insect-eaters suggests that other parts of the ecosystem are also faring well.
This is a strong endorsement of Bush Heritage’s management actions at Nardoo Hills Reserve and it will be fascinating to see if these trends continue in the coming years.
While such refuge areas are not necessarily lush, verdant oases, they are rich in critical resources. And if, as predicted, the drier and warmer climate we're now experiencing in south-eastern Australia foreshadows the future under rapid climate change, these woodland reserves and other Bush Heritage sites will be crucial to the survival of many of our native species.