CARPENTARIAN GRASSWRENS
After fire, Carpies can persist without spinifex as long as they can access rocky outcrops like these on Chidna Station. Note that the distant hills do not contain these important rocky features, and so no Carpies were found here after the fire.
Carpentarian Grasswrens (Amytornis dorotheae) have disappeared from about two-thirds of their range due to large wildfires. They are classified as Endangered; they have declined to only a few pairs in the Northern Territory and Boodjamulla (Lawn Hill) National Park in Queensland. This makes Chidna Station one of the last strongholds for the species.
FLAMMABLE HABITAT
Affectionately known as Carpies, these iconic birds rely on the spikey, almost cactus-like grass called spinifex (Triodia spp.). It's here they build their dome-shaped, woven grass nests, hide from predators and get respite from extreme heat. Compared to other grasses, spinifex is slow growing and only provides this protection after a few years. It's also highly flammable because the leaves contain a volatile resin, which is an adaptation to conserve water.
Dell, B., & McComb, A. J. (1979). Plant resins—their formation, secretion and possible functions. In Advances in botanical research (Vol. 6, pp. 277-316). Academic Press.
Henry playing Carpy calls to attract birds to the mistnet in order to be colour banded.
Colour Banding Carpies on Chidna Station.
LANDSCAPE CONFLAGRATIONS
Without fire, individual spinifex hummocks will often coalesce and form large continuous areas of cover. While this might sound like a good thing for Carpy conservation, it's a ticking time-bomb waiting to (literally) explode.
Over the past few decades, megafires have swept through the region, affecting all manner of plants and animals. Previous research on species similar to Carpies showed that post-wildfire population decline is caused not so much by immediate incineration, but by subsequent reduced nesting success, physiological impacts and elevated predation risk.
ROCK SOLID SUPPORT
Research from Conservation Partners ecologist and UQ PhD candidate Henry Stoetzel recently revealed that Carpies basically rely on two things after fire: (1) patches of unburnt spinifex within close proximity and/or (2) rocky outcrops, with small but deep cracks and overhangs. Despite their obvious differences, these features perform the same function: protection from predators and heat stress.
A megafire sweeps through Boodjamulla National Park in 2011. Carpies now persist in only a few places within the park.
Henry setting up the mist net in order to catch Carpies on Chidna Station.
SIMPLE STRATEGY
We have a pretty simple strategy to protect and enhance Chidna's Carpies: First, we need to ensure there are lots of unburnt spinifex patches available after the next wildfire. Second, we need to map and protect those rocky outcrops. Third, we need to reduce predation from feral cats near post-fire refugial areas. And fourth, we need to keep track of the Carpies themselves, to make sure our actions are having the desired impact. While conceptually simple, these actions are challenging to deliver.
FIGHT FIRE WITH FIRE
We are using prescribed burning to create a patchwork of different fuel age classes throughout Carpy habitat. We do this by burning during the storm season, when the soil is moist and rain to quell the fires is never too far away. This promotes a low intensity fire and aids rapid recovery of the spinifex and other plants, ensuring that enough cover is available for the Carpies, but reducing fuel loads at the same time.
ID BADGES
We are able to understand how individual Carpies are responding to our management using a key tool in our kit: colour-banding. It involves marking birds with a unique combination of colour bands fitted to their legs. This standard research practice allows us to follow the fate of known birds over time and to observe what happens when their territory is burnt. What is the impact of our management interventions on individuals?What is the optimal size and configuration of unburnt habitat? Without colour-banding, these questions could not be answered. And we must answer these questions if we are to successfully implement fire management that will optimise the habitat for Carpies and thereby increase their population size on Chidna.
A Carpy nest in a spinifex hummock.
Carpentarian Grasswren on Chidna Station.
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