Scientists have found direct evidence that grass seed-eating birds are sensitive to the repeated extensive, intense fires that currently affect northern Australia, but with implementation of appropriate fire management, it is possible to reverse the decline in health of their populations.
The striking Gouldian Finch, which once flew in flocks of 1000’s, is now so rare that it is listed as Endangered on the Environment Protection and Biodiversity Conservation (EPBC) Act.
Dr Sarah Legge, Chief Scientist for Australian Wildlife Conservancy (AWC) has made finding the reasons underlying the decline a research priority for the team at AWC’s Mornington-Marion Downs Wildlife Sanctuary.
“We really needed to find out what was making these birds tick and what we could do to make conditions better for them,” Dr Legge said.
Other researchers have previously suggested the decline in numbers could be due to increased stocking rates, increased wildfires, increased cat predation, disease or reduction in breeding habitat.
Due to AWC’s extensive work with fire in the Kimberley region through the successful EcoFire program (2004-2011) supported by Rangelands NRM, Dr Legge suspected that the mechanism underlying the decline of the species in the region hinged on the impact of unchecked wildfires.
“Not only were we able to confirm the lack of seed grass was a really important cause for the decline in Gouldians, but by applying the right management intervention we were then able to reverse the problem. So it was a very powerful bit of science and very useful for our management,” Dr Legge said.
Ecofire broad scale fire management
The extensive wildfires that have consumed the Kimberley over recent years have caused dramatic changes to the environment, modifying vegetation as well as having a significant negative impact on pastoral carrying capacity and biodiversity.
Working with neighbours, EcoFire implemented broad-scale fire management across a large landscape, with properties jointly conduct a prescriptive burning program to establish a mosaic of cool burns during the early dry season. These patchwork burns later act as firebreaks to any late season wildfire ripping through the region.
These extensive, intense fires that have typified fire patterns across much of northern Australia in recent decades, change the seed production of grasses, forcing seed-eating birds to fly further in search of food.
Seed grass eaters vulnerable after fires
Gouldian Finches are a specialist seed grass eater and nest exclusively in hollows of native trees, which means they are entirely reliant on the health and widespread diversity of native grass seeds in localised areas, especially during their nesting season. These preferences render Gouldian Finches more vulnerable to declines in seed availability than other seed-eating birds ‘ especially during nesting season.
AWC also carried out intensive surveys to monitor the health of local finch populations to determine if a change in the fire history (intensity, size, and frequency) had an impact on the health of the finch populations.
The researchers captured and completed a physical on thousands of Gouldian, Long-tailed and Double-barred Finches in two distinct locations with contrasting fire histories: one location had a high susceptibility to wildfires (but this was reduced over the course of the research through its inclusion in the EcoFire project) and the other location had a low susceptibility to wildfires due to topographical factors (i.e. contains riparian areas and ranges that act as natural fire breaks).
Rather than utilising the traditional bird count method, Dr Legge and her colleagues decided to adopt an innovative approach to determining how birds were faring by giving them a ‘physical’. The physical included blood tests, and measuring the amount of muscle and fat, as well as weights.
“What we found is that when birds are living in areas with frequent fire, they are adversely affected through the entire period from the late dry to the mid wet season,” Dr Legge said.
By the late dry grass seed is becoming scarce and finches have to fly much further to find enough food. Then, through the early to mid wet season, they began to lose condition, to the point where some individuals were dying around March.
This was happening because wildfire reduced the seed supplies in both the dry and the wet seasons. Intense wildfires were destroying much of the sorghum seed that the finches rely on during the dry season, so by the late dry, there was little food left.
During the early and mid wet season, Gouldian Finches rely heavily on spinifex seed to get them through until other grasses come into seed again. However, some spinifex species are very sensitive to fire and will only come into seed if left unburnt for 2-3 years, so frequently burnt areas have much lower seed availability.
The most telling part of the research was that as the incidence of fire was reduced between 2007 and 2011 thanks to EcoFire, the health indicators of the Gouldian Finch population increased.
Rangelands NRM has provided support to communicate and write up the results of this work.
AWC’s research has put a face on the need for fire management, as improved fire management regimes directly enhances both pastoral and biodiversity outcomes. Pastoralists, conservationists, Indigenous Rangers and the Department of Parks and Wildlife are increasingly working together to reduce the incidence of late dry season wildfires, however, fire remains one of the key land management issues of the Kimberley. AWC’s research has identified and personalised the impact of these wildfires on a beautiful and increasingly rare creature.
Image: Gouldian Finch. Phographer S Murphy, Australia Wildlife Conservancy.