Matt Herring, Kerstin Zander and Stephen Garnett, Charles Darwin University
When people think about threatened species conservation in agricultural landscapes it’s usually the most intact remnants of native vegetation that come to mind, but what about the novel habitats that farming creates? In the Riverina region of southern New South Wales, rice fields are providing a conservation opportunity where food production and threatened species can be managed concurrently.
One of the finest sounds of Australia’s wetlands is the deep, booming call from the Australasian bittern. It’s a sound now familiar to hundreds of Riverina rice growers. At first glance, irrigated agriculture and waterbird conservation may seem like strange bedfellows in the Murray-Darling Basin. But our research is looking at how water can be managed in a more integrated way, challenging the polarised debate of farming versus the environment.
Since the establishment of the Bitterns in Rice Project in 2012, the rice industry has gradually embraced this peculiar bird, and bittern-friendly rice growing is now a well-recognised concept. One grower from near Leeton, Milton Hoysted, recently said, “We’re tweaking the crop to better accommodate the bitterns. People chat about it with a bit of pride. I’ve got the birds, you haven’t. It’s turning into a bit of a competition.”
Bittern-friendly rice growing aims to maximise breeding success. Credit: Matt Herring.
One of our first challenges was to determine how many bitterns were using the rice fields. Given their cryptic nature, this involved some serious bittern-sleuthing. After hundreds of surveys across randomly selected farms we crunched the numbers and the results were remarkable. We found that in most rice seasons about 500 to 1000 bitterns make the crops their home. That’s about 60% of the national population and 40% of the global population, making rice growers a key custodian of the species, alongside managers of natural wetlands.
It turns out that the way rice is grown provides conditions similar to the shallow swamps with which the bitterns are familiar. The rice season starts with bare paddocks that are sown and flooded, and then two or three months later, once there are sufficient cover and prey, one of the world’s most threatened waterbirds is nesting. The rice fields essentially function as ephemeral wetlands where the early successional stage is restarted each year because of drying and harvest, sowing and flooding.
Satellite tracking of bitterns revealed that at harvest time many disperse to coastal wetlands, while others stay local, seek-ing out habitats like vegetated channels and storage dams. Credit: Matt Herring.
The window for bitterns to breed successfully before harvest can, however, be tight. Most nesting commences in the rice field from mid-December to mid-January, and from there it’s almost three months before the chicks fledge, with harvest usually peaking around mid-April. Growers are under pressure due to considerations of water-use efficiency to contract the period when the fields have ponded water. New shorter-season varieties have been bred, and a trend is growing to delay the commencement of ponding.
What we’ve found is that if growers can flood their fields in October, and provide at least 130 days of ponding, then the chicks are able to fledge before harvest. Fortunately, Riverina Local Land Services, through funding from the Australian Government’s National Landcare Program, have begun offering financial incentives for bittern-friendly rice growing, drawing on the results of our research.
The focus is on getting the birds nesting as early as possible and maximising breeding success. Small patches in the crop, where additional urea fertiliser has been used, create taller, thicker rice and encourage earlier nesting, while the management of adjacent wetland refuges, such as vegetated channels and storage dams, complement the rice fields and provide habitat beyond the rice season. Maintaining grassy banks provides roaming chicks with cover from predators, and control programs for foxes and cats are being planned.
The bitterns and their use of rice fields highlight how novel habitats can be overlooked, but also that there are hidden opportunities to work together for threatened species conservation on private land.
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The Bitterns in Rice Project is a collaboration between the Rice Growers’ Association of Australia and Birdlife Australia, with key support from the Riverina Local Land Services, Norman Wettenhall Foundation, Coleambally Irrigation, Murrumbidgee Field Naturalists Club, the Rural Industries Research and Development Corporation, the Murray Local Land Services, Murray Irrigation, Murrumbidgee Irrigation, Murrumbidgee and Coleambally Landcare, and the New South Wales Office of Environment & Heritage. Matt’s research is part of the Threatened Species Recovery Hub of the Australian Government’s National Environmental Science Program.