Bitterns in rice A pilot study of the endangered Australasian and its use of rice crops

MAY 2014 RIRDC Publication No. 14/007

Bitterns in rice A pilot study of the endangered ( poiciloptilus) and its use of rice crops

by Matthew W. Herring, Neil Bull and Andrew Silcocks

May 2014

RIRDC Publication No. 14/007 RIRDC Project No. PRJ-007956

© 2014 Rural Industries Research and Development Corporation. All rights reserved.

ISBN 978-1-74254-623-0 ISSN 1440-6845

Bitterns in Rice: A pilot study of the endangered Australasian Bittern (Botaurus poiciloptilus) and its use of rice crops Publication No. 14/007 Project No. PJR-007956

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Researcher Contact Details

Matthew Herring Murray Wildlife PO Box 48 Katoomba NSW 2780

Email: [email protected]

In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form.

RIRDC Contact Details

Rural Industries Research and Development Corporation Level 2, 15 National Circuit BARTON ACT 2600

PO Box 4776 KINGSTON ACT 2604

Phone: 02 6271 4100 Fax: 02 6271 4199 Email: [email protected]. Web: http://www.rirdc.gov.au

Electronically published by RIRDC in May 2014 Print-on-demand by Union Offset Printing, Canberra at www.rirdc.gov.au or phone 1300 634 313

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Foreword

Little is known of the value of Australian rice crops as habitat for threatened species. The Australasian Bittern is one of Australia’s most threatened species of . Globally, they are listed as endangered by the IUCN (International Union for the Conservation of Nature). The Commonwealth Government, under the Environment Protection and Biodiversity Conservation Act, has listed the Australasian Bittern as endangered. The most recent population estimate for Australia was found to be only 250-800 . Rice crops have been known to provide habitat for bitterns, but the relative importance and conservation value of these habitats was unknown.

This study has indicated that there is likely to be widespread breeding of the Australasian Bittern in rice crops. In total, 70 individuals were confirmed using rice crops in the of during the 2012-13 rice season. A preliminary estimate of 500-1000 across this rice-growing region indicates this is easily the largest known population of the Australasian Bittern ever recorded. If these bitterns are breeding successfully and constitute a sustainable population, it represents the discovery of the global stronghold for the species.

Rice farmers have the opportunity to take the lead on bittern conservation, demonstrating large scale marriage of food production and nature conservation. The development of bittern-friendly rice-growing guidelines will be crucial for the bird’s management. Initial indications are that aerially sown rice planted early in the season, with sympathetic management of Cumbungi (Bull rush), will benefit bitterns. Outside the rice-growing season, the management of bittern habitat in storage dams, channels and natural will also benefit this endangered waterbird and other biodiversity.

This report is an addition to RIRDC’s diverse range of over 2000 research publications and it forms part of our Rice R&D program, which aims to improve the profitability and sustainability of the Australian rice industry.

RIRDC’s publications are available for viewing, free downloading or purchasing online at www.rirdc.gov.au. Purchases can also be made by phoning 1300 634 313.

Craig Burns Managing Director Rural Industries Research and Development Corporation

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About the Authors

Matthew Herring is an ecologist at Murray Wildlife. He has been working on waterbird and conservation since the late 1990s, with a focus on farms in the southern Murray-Darling Basin.

Neil Bull is the Regional Coordinator (Murray) of the Environmental Champions program at the Rice Growers’ Association of Australia and has been a rice farmer for over 30 years.

Andrew Silcocks is a Project Manager at BirdLife Australia and leads the Bittern Project that began in 2007 to inform conservation efforts for Australia’s threatened bitterns. Acknowledgments

Funding and support for this study was provided by the Rural Industries Research and Development Corporation Rice Program, the Murrumbidgee and Murray Catchment Management Authorities, the Rice Growers’ Association of Australia, BirdLife Australia, Coleambally Irrigation, Murrumbidgee Irrigation, Murrumbidgee Landcare, the Murrumbidgee Field Naturalists Club and the New South Wales National Parks and Wildlife Service. Thanks to all of the rice farmers that supported the study so enthusiastically and shared their knowledge of bitterns. Mark Robb and Daryl Gibbs were integral in canvassing support from rice farmers in the Murrumbidgee and Coleambally rice-growing areas. We thank other members of the ‘Bitterns in Rice’ steering committee: Kimberley Beattie, Keith Hutton, Karen McCann, Max O’Sullivan, Janelle Ruggeri, Arun Tiwari, Rick Webster and Anna Wilson. Thanks also to Jason Tasker (Murray Irrigation) who helped prepare the maps and John Peter (BirdLife Australia) for proof reading a draft of this report.

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Contents

Foreword ...... iii About the Authors ...... iv Acknowledgments ...... iv Executive Summary ...... vi Introduction ...... 1 Objectives ...... 3 Methodology ...... 4 Community engagement to elicit sightings and their verification ...... 4 Establishment of primary study sites ...... 5 Breeding ...... 5 Bittern surveys and estimating their abundance in rice crops ...... 6 Rice crop characteristics, rice-growing techniques and surrounding habitat ...... 6 Other Fauna ...... 7

Results and Discussion ...... 7 Breeding ...... 7 Bittern surveys and estimating their abundance in rice crops ...... 10 Rice crop characteristics, rice-growing techniques and surrounding habitat ...... 16 Other Fauna ...... 19

Implications and Recommendations ...... 20 References ...... 22

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Executive Summary

What this report is about The Australasian Bittern (Botaurus poiciloptilus) is an endangered waterbird known to use rice crops in the Riverina region of New South Wales. The relative importance and conservation value of these habitats for this species was previously unknown. Potentially, rice farmers can make a significant contribution to the conservation of Australia’s ‘Bunyip Bird’.

Who is this report targeted at? This report is targeted at the rice industry and organisations involved in the environmental management and ecological sustainability of rice farms, such as government departments, regional bodies and Landcare groups.

Where are the relevant industries located in Australia? The Australian rice industry is centred on the Riverina, in the Murray, Murrumbidgee and Coleambally regions. The Australian rice industry has the capacity to produce more than 1 million tonnes of rice per year. Australian rice is milled, packed and branded in the Riverina by SunRice, which then exports Australian rice products to world markets.

Background The Australasian Bittern occurs in Australia, New Zealand and , and is listed globally as Endangered by IUCN. The identification of important areas for the Australasian Bittern, where the largest concentrations occur and where conservation efforts can be prioritised, is urgently needed. The most recent population estimate for Australia is a cause for concern, at only 250—800 birds.

Aims/objectives 1) To establish if the Australasian Bittern breeds in Riverina rice crops 2) To estimate the number of the Australasian Bitterns that inhabit Riverina rice crops 3) To establish what agronomic practices create the best breeding habitat for this species 4) To establish if there are links with the environmental assets of rice farms (vegetation or wetlands) to the birds use of rice crops 5) To establish if there are links with other crops or agriculture infrastructure to the birds’ use of rice crops.

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Methods used Community engagement was used to elicit sightings and establish bittern study sites in rice crops. This resulted in 34 sites in the Murrumbidgee area (including Coleambally), while the paucity of sightings in the Murray area necessitated supplementary sites there. A total of 63 rice paddock study sites were established (34 in the Murrumbidgee and 29 in the Murray). The presence of bitterns was verified through 1-hour surveys and a range of habitat and fauna data were also collected. Further surveys were undertaken to record breeding.

Results/key findings No conclusive evidence of breeding was recorded, but rather than reflecting a lack of breeding activity, it is believed that this reflects the difficulty of studying this cryptic species. A range of factors indicate that there is likely to be widespread breeding by the Australasian Bittern in rice crops. A total of 27 bitterns were recorded at 17 of the 63 sites during the 1-hour surveys. An additional 7 of the 63 sites yielded verified bitterns at other times for a total of 47 bitterns. A further 23 bitterns were confirmed at other sites, where the risk of double counting was considered negligible, so a total of 70 individual bitterns were found in rice crops during the 2012—13 season. The Coleambally irrigation district supported the largest concentration with 49 birds, and a separate study was undertaken to resample the population there and estimate abundance. A preliminary estimate of 500—1000 Australasian Bitterns that used Riverina rice crops during the 2012—13 season was recorded. This is the largest population ever recorded, and if these bitterns are breeding successfully and constitute a sustainable population, it represents the discovery of a global stronghold for this endangered species. Initial indications are that aerially sown rice planted early in the season, with sympathetic management of Cumbungi () or Bull Rush, will benefit bitterns. Outside of the rice-growing season, the management of bittern habitat in storage dams, channels and natural wetlands will also benefit this endangered waterbird and other biodiversity. No links with other crops or agricultural infrastructure were found. The most noteworthy additional species found was the nationally endangered Australian Painted Snipe, with a total of 44 birds recorded across five sites. The importance of rice crops to this species was not previously recognised and further highlights the potential role of the rice industry in waterbird conservation.

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Implications and Recommendations • Conservation efforts for the Australasian Bittern should be reprioritised to focus on rice farms and rice farmers. The rice industry can seize the opportunity to take the lead on bittern conservation, embracing the responsibility and supporting its growers to adopt bittern-friendly rice-growing practices where practical, as they are identified. The continued and expanded engagement of rice farmers to increase their awareness and appreciation of the plight of bitterns will be crucial in the uptake of bittern-friendly rice- growing practices • A population monitoring program should be developed as soon as possible, and a more accurate population estimate produced • Additional research should focus on five areas: (1) the breeding ecology of bitterns in rice crops; (2) the diet and foraging ecology of bitterns in rice crops; (3) the movement patterns of bitterns after harvest and during winter; (4) identification of the rice-growing techniques that benefit bitterns most; and (5) the use of rice crops by the endangered Australian Painted Snipe and opportunities to merge monitoring and conservation programs for these species • Explore commercial opportunities, such as a rice variety known as ‘Bittern’, and the inclusion of the species in the marketing of rice products • Highlight the environmental benefits of rice production, notably the significant provision of habitat for threatened species.

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Introduction

The Australasian Bittern (Botaurus poiciloptilus) is an unusual waterbird. It is a rarely seen and poorly-known species, mainly because of its secretive nature. It is a cover-dependent waterbird that feeds, roosts and breeds in wetland areas with dense water plants. The booming call of male bitterns during the breeding season is thought to have helped give rise to legends of the bunyip—a mythical creature embedded in numerous Indigenous Australian cultures, whose stories were accepted and enhanced by European colonisers (Marchant and Higgins 1990; Holden 2001).

The Australasian Bittern is one of four Botaurus species found in the world and the only one that occurs in Australia. The (Botaurus pinnatus), the (Botaurus lentiginosus) and the Great (or Eurasian) Bittern (Botaurus stellaris) are also secretive waterbirds associated with wetlands supporting abundant water plant cover. The Australian mainland supports two resident bittern species from the : the Black Bittern (Ixobrychus flavicollis), which occurs in coastal parts of northern and eastern Australia; and the Little Bittern (Ixobrychus dubius), found primarily in south-eastern Australia, including the Riverina but it is not known to use rice crops (Kushlan and Hancock 2005).

The Australasian Bittern occurs in Australia, New Zealand and New Caledonia, and is listed globally as endangered by the International Union for Conservation of Nature (IUCN) (BirdLife International 2012). The main cause of its threatened status is the loss and degradation of wetland habitat. Until recently, Australia was thought to support 2500 mature individuals, with 2000 in south-eastern Australia and 500 in south-. This is considerably more than New Zealand, with 580–725 birds, while in New Caledonia, there are only two recent records, with an estimated 0–50 individuals (Garnett and Crowley 2000; Wetlands International 2006; BirdLife International 2012). In March 2011, the Australasian Bittern was formally listed as endangered in Australia following strong evidence for a substantial decline to an estimated total population of 250–800 individuals at the end of a prolonged national drought (SEWPaC 2011).

The identification of important areas for the Australasian Bittern, where the largest concentrations occur and where conservation efforts can be prioritised, is urgently needed (Hafner et al. 2000; Kushlan and Hancock 2005; Garnett et al. 2010). The use of rice (Oryza sativa) crops by the Australasian Bittern in the Riverina in New South Wales has been recognised since at least 1984 (Disher 2000). However, their abundance in this habitat, its relative conservation value, the factors determining their use of rice crops and the extent to which they breed in it remain poorly known. The known value of rice crops for their closest

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relative, the , formerly considered a reed-bed specialist, has risen substantially, with breeding now commonly recorded in rice crops in northern Italy (Longoni et al. 2007, 2011).

Commercial rice-growing began in New South Wales in 1924, with major development during the 1960s and 1970s. Rice is grown from October to May in irrigated bays with water diverted from rivers through networks of channels. The amount of rice grown varies greatly between years and depends on the amount of water available for irrigation, designated through regional allocations and individual entitlements. From 1979–2002, 16 of 24 seasons exceeded 80 000 ha planted to rice, with a maximum of approximately 180 000 ha in 2000–01. From 2003–10, during a severe drought, only two of eight seasons exceeded 40 000 ha, with a minimum of 2160 ha in 2007–08, producing the smallest harvest since 1929. The 2010–11 crop was 83 327 ha, and the 2011–12 crop 108 850 ha, while in 2012–13 it was approximately 113 000 ha, the largest since 2001–02. Approximately 95% of Australia’s rice is grown in the Riverina, of which the Murray Valley typically supports around 40%, with 38% in the Murrumbidgee region, and 22% in the Coleambally region (RGA 2013; SunRice 2013; SunRice, unpublished data).

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Objectives

1) To establish if the Australasian Bittern breeds in Riverina rice crops 2) To estimate the number of these birds that inhabit Riverina rice crops 3) To establish what agronomic practices create the best breeding habitat for this species 4) To establish if there are links with the environmental assets of rice farms (vegetation or wetlands) to the birds use of rice crops 5) To establish if there are links with other agriculture crops or infrastructure to the birds use of rice crops.

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Methodology

Community engagement to elicit sightings and their verification In order to answer the questions that arise from each of the five objectives, community engagement to elicit sightings was vital. The Bitterns In Rice Project Committee, which comprised key representatives from across the rice-growing region (see acknowledgements), encouraged the reporting of bittern sightings in rice crops through their respective networks. In particular, the regional RGA Environmental Champions Coordinators, Neil Bull (Murray) and Daryl Gibbs (Murrumbidgee), along with Mark Robb (Coleambally Irrigation), appealed to rice farmers to keep their ‘eyes and ears peeled’ during the season and urged them to report their sightings. Once field work commenced in December 2012 (e.g. verification of sightings, habitat surveys), Matthew Herring was also on the ground finding birds, encouraging reports from rice growers and asking them about their knowledge of the species. The committee was updated on the results throughout the season.

Early in the 2012—13 season (November and December 2012), two media releases were circulated and three field days held. The media releases resulted in local newspaper and radio features, such as The Area News (Griffith) and ABC Riverina interviews, along with widespread promotion online, such as the websites of Murrumbidgee Landcare and BirdLife Australia, the latter supporting an online report form for sightings in rice, developed by Andrew Silcocks. The period leading up to Christmas Day is a time when bitterns are booming and the rice has not yet grown tall enough to make observation prohibitively difficult.

From the reported sightings, a verification process was undertaken to help establish Australasian Bittern study sites where targeted bittern surveys took place and a range of other data were collected (see other methods). The most important part of the verification process was eliminating Nankeen Night- (Nycticorax caledonicus) that had been misidentified as Australasian Bitterns, which is a common occurrence. This was usually easily achieved, often during phone conversations, with most of these erroneous sightings identified because of the large number of birds seen (Australasian Bittern do not occur in flocks), typically flying in to rice crops on dusk or seen at night while spotlighting, and the presence of birds roosting in trees (Australasian Bitterns do not roost in trees). Approximately 80% of the verified sightings used in this study were those confirmed by Matthew Herring during the field work, with the majority of additional verification by Mark Robb (Coleambally).

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Establishment of primary study sites As a result of the community engagement in November and December, study sites were established through the verification process—the following-up of reported birds not considered to be Nankeen Night-herons or other erroneous reports. However, in order to cover the two regions evenly and meet an agreed funding requirement of approximately 30 sites in each of the Murray and Murrumbidgee (including Coleambally), this was only possible for the Murrumbidgee area because of the paucity of credible reports from the Murray. For the Murray, four sites were follow-ups as part of the verification process, with the remainder selected to encompass the area, particularly at sites known to support bitterns in rice in previous years.

A study site was a discrete rice paddock encompassing multiple bays and greater than 30 metres from an adjacent rice paddock. When a study site yielded a bittern during the follow-up survey, a control site—the nearest rice paddock—was established adjacent to it, though this was not always immediately possible.

A total of 63 study sites were established between 11 December 2012 and 8 February 2013, with 34 in the Murrumbidgee (including Coleambally) and 29 in the Murray. Of the 34 in the Murrumbidgee, 10 were control sites, while three of the 29 Murray sites were controls. Ultimately, the controls were of little value for comparative purposes, not least because four of them (31%) yielded bitterns during the 1-hour surveys.

At each of the 63 study sites, a range of data pertaining to the survey (e.g. date, time, temperature), bitterns (e.g. number seen, behaviour, historic sightings), habitat (e.g. water depth, rice height, extent of cumbungi in toe furrows) and surrounding landscape features (e.g. nearby wetlands, adjacent supply channels) were collected.

Breeding These methods relate to the first objective. Little is known about the breeding of Australasian Bittern in rice crops and their cryptic nesting behaviour necessitated an adaptive approach to confirm breeding in the 2012—13 rice-growing season. Searches for nests and other evidence of breeding began in February 2013 once all 63 primary study sites had been surveyed. The focus of these breeding surveys were sites where more than one bird had been seen and a male had been heard regularly. Booming males are indicative of breeding activity and although males are not thought to participate in incubation or rearing of young, they do remain within their territory, presumably to defend it (Marchant and Higgins 1990; Kushlan and Hancock 2005). Key sites in Coleambally were targeted, along with a Wakool site and a Leeton site. Where birds had been seen in the same vicinity, such as the same part of a particular bay, over a period

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of weeks, or where they were seen in the same location for longer than 20 minutes during the breeding survey, the area was searched on foot, wading through the rice.

Despite considerable effort over several days, these surveys failed to confirm any nests or other evidence of breeding. On 13 March 2013, a helicopter was hired for two hours to trial an aerial approach to identifying nests. Because of the cluster of key sites around Coleambally (see Results), this area was chosen for aerial surveys. Additionally, as harvest time approached, rice farmers were encouraged through internal RGA communication networks to record any evidence of bittern breeding while harvesting.

Bittern surveys and estimating their abundance in rice crops These methods relate to the second objective. A combination of sightings reported by rice growers, verified by targeted bittern surveys, and additional birds found during field work were used to estimate the number of Australasian Bitterns that used rice crops in the Riverina of New South Wales during the 2012—13 rice-growing season. A concurrent study focussed on the Coleambally irrigation district because of the relatively large number of birds found there early in the season (Herring et al. in press). This separate study helped to infer and define the parameters for the estimate for the broader region.

Targeted bittern surveys at each of 63 primary study sites were conducted by Matthew Herring once within 3 hours after first light or before sunset to maximise the likelihood of detection, because of the crepuscular and part-nocturnal nature of the species. There were six exceptions in the afternoon, where surveys were conducted outside of the 3 hour window. The surveys were conducted between 11 December 2012 and 8 February 2013, and involved one hour of scanning for birds from banks adjacent to rice bays in a vehicle and on foot, as well as listening for booming males. Double counting was avoided in the collation of final figures for each region and the total for the rice-growing area. For example, birds recorded during harvest at new sites were not included because they may have been previously counted at existing sites and moved.

Rice crop characteristics, rice-growing techniques and surrounding habitat These methods relate to the third, fourth and fifth objectives. Initially, we intended to collect a wider range of data relating to factors that may affect the use of rice crops by Australasian Bitterns. However, this was not possible due to time constraints, so a subset of these data were prioritised. Before the formal surveys commenced at the 63 study sites and early on during those

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surveys it became clear that some of the factors we considered potentially important were not. These were subsequently withdrawn from the standard data collection at the 63 sites and included: the proximity to natural and constructed wetland areas and their extent; the distance to regular human disturbance (house, shed, track, and road); the activity of scare guns and regularity of shooting activity; and the extent of surrounding tree cover. Some of these factors can be explored remotely at a later date using aerial photographs and satellite maps, but the early indications were that their overall influence on bitterns was likely to be minimal and a cursory exploration of the final data supports this. For example, a relatively large number of bitterns were found in rice paddocks with active scare guns, adjacent to roads or houses and a large distance (>20 km) from natural or constructed wetland areas with suitable bittern habitat, with the exception of other rice crops.

The extent of rice crops at various scales surrounding each study site is likely to be important in determining bittern use and abundance. It can also be investigated remotely at a later date using industry data and imagery.

At each of the 63 sites, water depth, crop height and aerial cover measurements were taken in two different bays that formed part of the rice paddock study site. When a bittern was observed or the location of a booming male was clear, measurements in those bays were taken. The extent of Cumbungi (Typha) in toe furrows was estimated to the nearest square metre. A description of the presence of weeds within the rice crop and on banks was taken.

Other Fauna All vertebrate fauna were recorded incidentally during the 1-hour surveys at the 63 sites. This primarily entailed other species of waterbirds and . These methods do not relate directly to any of the objectives, but they are an important component of this overall pilot study because some species represent likely prey, indicator species and others are also of conservation significance.

Results and Discussion

Breeding Despite considerable effort, no conclusive evidence was found that the Australasian Bittern bred in rice cops during the 2012—13 season. Rather than being suggestive of a lack of breeding activity, we believe this highlights the difficulty in gathering information on breeding for this cryptic species. There are a number of key reasons that we believe justify the inference that

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Australasian Bitterns breed in rice crops commonly and successfully, and that they did so during the 2012—13 season.

There are already credible records of breeding by the Australasian Bittern in rice crops in the Riverina. For example, a nest was found near in the late 1990s prior to the drought (Phil Maher, pers. comm.) and fledglings were found during harvest near Murrami in 2011 (Lindsay McClure pers. comm.). Their closest relative, the Eurasian Bittern, is now commonly recorded breeding in rice crops in northern Italy (Longoni et al. 2007, 2011).

The rice-growing season (October to May) coincides with the Australasian Bittern breeding season (October to February), and booming males, which were frequently recorded, are indicative of breeding activity (Marchant and Higgins 1990; Kushlan and Hancock 2005). In the Coleambally region, where the majority of bitterns were found, there is a distinct lack of alternative habitat where breeding could occur, such as remnant wetlands or channels with reed beds. Most of the local rice growers consulted during the 2012–2013 season who were familiar with the Australasian Bittern indicated the presence of the species over numerous, consecutive years. It is unlikely that such a relatively large number of birds would position themselves where successful breeding was not feasible based on their experience.

Booming activity peaked in late December and early January. At this time, rice crops in the Coleambally region were 40–50 cm high, providing ample cover for the birds, material for nest construction and concealment. Eurasian Bitterns have been shown to delay their breeding until there is sufficient cover (when rice height is around 35 cm), and no notable difference in breeding success between rice crops and earlier reproduction in natural wetlands has been observed (Longoni et al. 2007). In New Zealand, peak booming activity appears to be a precursor to peak laying and hatching (O’Donnell 2011). Incubation is purported to be around 25 days, with chicks fledging at about 49 days (Heather and Robertson 2000; Kushlan and Hancock 2005), though O’Donnell (2011) could not determine the source of these figures. The relatively well-studied Eurasian Bittern lends some support, with incubation of about 26 days and chicks fledging at around 53 days (Cramp and Simmons 1977; Gilbert et al. 2007). It is reasonable to presume there is a sufficient window of opportunity for Australasian Bitterns to breed successfully in rice crops if are laid in late December because it is approximately 110 days before peak harvest in mid-April. It appears Australasian Bitterns have adapted their breeding strategy to fit the rice growing season. This may include delayed breeding and altered movement patterns. Regular coastal influxes in winter around Melbourne and Geelong (BirdLife Australia, Atlas database) may represent post-breeding birds originating from the after the rice has been harvested.

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During the 2-hour helicopter flight on 13 March 2013, eight bitterns were flushed and several structures were found that may have been old Australasian Bittern nests. Subsequent on-ground visits to these possible bittern nests also revealed other less substantial structures that were probably feeding or roosting platforms, along with additional unidentified old waterbird nests. At one old nest however, an unhatched, water-damaged was found. The egg dimensions and lack of pattern indicated the egg and the nest from which it was collected were that of either an Australasian Bittern or a Swamp Harrier (Circus approximans), and this backed up by consultation with other experts (David Hollands, Phil Maher). At most of the structures, including the old nest with the egg, thought to be those of bitterns were found.

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Bittern surveys and estimating their abundance in rice crops A total of 27 Australasian Bitterns from 17 of the 63 primary study sites were recorded during the 1-hour surveys (Table 1, Figures 1—2). Coleambally was clearly the most important region, which is why a separate study was undertaken to randomly resample the population there to more accurately estimate abundance (Herring et al. in press). The Murray supported relatively low numbers, with only 10% of sites yielding a bittern record, at an average of 0.14 birds per survey, while the Murrumbidgee (not including Coleambally) supported intermediate numbers, with 23% of sites yielding bittern records, at an average of 0.31 birds per survey (Table 1).

An additional seven of the 63 sites yielded a confirmed record of bitterns outside of the 1-hour survey, bringing the total number of primary study sites with confirmed records of bitterns to 24. The total number of recorded at these 24 sites was 47 birds. In addition to these 47 birds, a total of 23 birds was verified at other sites where the risk of double counting was considered negligible, so the total number of verified bitterns for the study was 70 birds (Table 2). At the sites where these 70 individuals were recorded, the actual number is likely to have been considerably higher because of limited survey effort and low detectability. This is a species notoriously difficult to detect. Additional work at some of the sites, where only one or two birds were initially recorded, produced up to six individuals.

Table 1: Summary of Australasian Bittern records from the 1-hour surveys across the three rice-growing regions in the Riverina during the 2012—13 season.

Average Number Total Number Number of Bitterns Per Number of Sites with REGION of Bitterns 1-hour Survey of Sites Bitterns

Murrumbidgee 13 3 (23%) 4 0.31

Coleambally 21 11 (52%) 19 0.90 Murray 29 3 (10%) 4 0.14

TOTAL 63 17 (27%) 27 0.43

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Table 2: Total number of confirmed Australasian Bitterns in rice crops during the 2012—13 season, including sightings during and outside the 1-hour surveys at the 63 primary study sites, as well as sightings at additional sites, such as those in the separate Coleambally population study (Herring et al. in press). Note: Double-counting has been avoided and these numbers represent individuals, not sightings.

Number of Number of Bitterns at Bitterns at Total Number REGION Primary Study Additional of Bitterns Sites Sites Murrumbidgee 9 8 17 Coleambally 34 15 49 Murray 4 0 4 TOTAL 47 23 70

Undoubtedly, the drought of 2001–10 had a severe impact on Australasian Bittern populations. During the 1990s, Australasian Bitterns were commonly recorded in rice crops around Deniliquin in the Murray Valley, and then they declined markedly during the drought (Phil Maher, pers. comm.). The four individuals verified in rice crops of the Murray suggest limited or no recovery. The area planted to rice in the Murray is usually at least 100–200% greater than at Coleambally region, but during the drought Coleambally had rice-crop areas similar to or larger than the Murray for five of the ten years (SunRice, unpublished data). The Murray is approximately 15 times larger than Coleambally, so the relatively sparse distribution of Murray rice crops was especially pronounced during the drought. One plausible explanation for the concentration of Australasian Bitterns in Coleambally, compared to the Murray, is the favourable water allocations during the drought. This may have resulted in the continued seasonal presence of sufficiently concentrated areas of rice to maintain a population capable of recovery. Population trends in Coleambally are unknown, and although it is reasonable to assume that the population has increased substantially since the drought ended, most local rice farmers familiar with the species saw and heard them every year, including during the drought. In 2009, one Coleambally rice paddock supported 11 birds (David Webb, pers. comm.). The Murrumbidgee region shared the favourable water allocations during the drought with Coleambally and its rice crops are similarly concentrated, but there are extensive areas of alternative Australasian Bittern habitat in the Murrumbidgee region, which may account for fewer birds using rice crops. However, they also appear to have declined in the Murrumbidgee region, where they were regularly recorded in rice crops around Leeton during the 1990s and

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until 2008, followed by a sharp decline to relatively low numbers that remained unchanged during the 2012—13 season (K. Hutton, pers. comm.).

The 17 birds verified in rice crops in the Murrumbidgee region during the 2012–2013 season is approximately one third of the number found in Coleambally (Table 2). Survey effort was greater in Coleambally, which may account for some of this difference, although the mean of 0.31 birds per 1-hour survey in the Murrumbidgee region suggested a density of approximately one third that of Coleambally (Table 1). It is unclear whether the Murrumbidgee sites were representative of that region and further work will be crucial for more accurate estimates, but extrapolation at this early stage is still useful. The Murrumbidgee region supports an average of approximately 72% more rice area than Coleambally (SunRice, unpublished data), so a preliminary estimate of the number of bitterns in the Murrumbidgee region using these data would be 57% of the number found in Coleambally (0.33 x 1.72). The separate Coleambally study indicated a minimum of approximately 362 individuals prior to breeding (Herring et al. in press), so the additional 57% in the Murrumbidgee region would be 206 birds for a total minimum of 568 in Coleambally and Murrumbidgee regions. In the Murray, an unknown number of additional birds beyond the four verified in this study also occurred. The 63 primary study sites accounted for less than 3% of the 113 000 ha of rice grown in the 2012—13 season and yielded 27 birds during the 1-hour surveys and a total of 47 at other times (Table 1 and 2). In Coleambally, the primary study sites (where records were being verified) produced on average about three times as many birds (19 birds at 21 sites versus 9 birds at 30 sites) during the 1-hour surveys as randomly selected sites (Table 1, Herring et al. in press). If we extrapolate those parameters across rice in the Riverina we get 297 birds (27 birds x 0.33 x 100/3) for 1- hour surveys (where a large number of birds inevitably remain undetected), and 517 birds (47 birds x 0.33 x 100/3) for the total number of individuals recorded.

A preliminary total estimate of the number of Australasian Bitterns using rice crops across the Riverina during the 2012—13 season of 500—1000 individuals is reasonable, but further work to refine this figure is critical. The minimum of 500 is considered conservative but would still easily account for the largest known population of the Australasian Bittern ever recorded. The significance of the confirmation of 70 individuals in rice crops and the subsequent estimates are best demonstrated by the two most recent total population estimates for Australia of 250–800 and 2500, respectively. Bool Lagoon in is arguably the most important individual site in Australia (BirdLife International 2012), with surveys in 2011 revealing a minimum of 20 booming males (BirdLife Australia, Atlas database). In New South Wales, Lake Cullival and the adjacent lower Boree Creek floodplain near Urana supported an estimated 25– 40 birds in 2000 (Matthew Herring, unpublished data), while Hird Swamp, near Cohuna in , supported an estimated 50–100 individuals during the summer of 2002–03 at a time of

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severe drought (Rogers et al. 2005). In Australia, we are unaware of any individual wetland, wetland complex or area of comparable size to the Riverina rice-growing region ever known to support more than 100 individuals. The Whangamarino wetland in New Zealand covers 7290 ha and is considered the most important Australasian Bittern site in that country, supporting 20% of the nation’s breeding population. There, an average density of one bird per 49 ha has been recorded, suggesting a total of 148 birds (Ogle and Cheyne 1981, cited in Whiteside 1989; DOC 2013).

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Figure 1: Location of bittern records from the 29 primary study sites in the Murray region.

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Figure 2: Location of bittern records from the 34 primary study sites in the Murrumbidgee region (including Coleambally).

Future population estimates and monitoring should incorporate the insights into survey efficiency that arise from this study. Surveys beginning in December proved to be successful in detecting birds before the rice had grown tall enough to make observation prohibitive. The early

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morning and late afternoon surveys using a combination of walking and surveying from a motor vehicle were successful in finding a relatively large number of bitterns with minimal effort. Unlike nocturnal surveys, they have the added benefit of visual identification. Figure 3 demonstrates that booming males and visual identification (‘Bitterns No Boom’) were more likely in colder temperatures. This is primarily an artefact of the successful morning surveys when bitterns were often seen and males were often recorded booming, and temperatures were low.

100%

90%

80% Bitterns Boom 70%

60%

50% Bitterns No Boom

40%

30% No Bitterns 20%

10%

0% 14-20 °C (n=16) 21-27 °C (n=34) 28-34 °C (n=23) 35-46 °C (n=20)

Figure 3: Proportion of bittern records, including booming males and visual identification, in four temperature categories for the 63 primary study sites and the 30 Coleambally random sites (Herring et al. in press).

Rice crop characteristics, rice-growing techniques and surrounding habitat Rice crops are relatively homogenous wetland habitats, with little variation in their structure and management. The shortest crop height recorded with a bittern present was 30 cm (Table 3), reflecting the species’ dependence on cover. The earlier that crops are sown the sooner there will be potential bittern habitat with sufficient cover, material and concealment for nesting.

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Bitterns were recorded in a range of water depths, from 10—31 cm. They were not recorded in dry bays where water-saving measures were being employed, nor in younger crops sown later in the season. However, there was no notable difference between the means for the 18 measurements of rice height, water depth and rice cover recorded when one or more bitterns were present in a bay (Table 3), and the means for the remaining 108 measurements recorded when bitterns were not known to be present (43.1 cm for rice height; 14.3 for water depth; and 46% for rice cover).

Table 3: Rice height, water depth and rice cover (%) measurements for 18 rice bays (from 18 separate rice paddocks) with one or more bitterns present.

Rice Height Water Depth Rice Cover (cm) (cm) (%)

33 11 35 48 14 75 55 23 50 41 13 50 42 13 60 30 12 60 31 18 40 53 14 80 31 18 40 46 11 40 46 20 15 60 25 80 35 20 20 38 13 65 59 31 25 37 10 40 56 28 60 39 5 45 MEAN MEAN MEAN 43.3 cm 16.6 cm 48.9% A total of 18 of the 63 primary study sites (29%) contained at least 1 m2 of Cumbungi within the toe furrows of the rice bays at the time of surveying. During the 1-hour surveys, six of those 18 sites (33%) yielded bitterns, while 11 of the 45 (24%) non-Cumbungi sites also yielded bitterns. Bitterns were often recorded using Cumbungi within rice bays during the study, and although it is reasonable to assume it is important additional habitat in rice crops, the results suggest it is certainly not necessary to support bitterns. Of note however, is that the three sites with the largest areas of Cumbungi (250 m2, 500 m2 and 800 m2) were all known to support bitterns. The retention of Cumbungi within the toe furrows of rice bays (i.e. avoiding spraying) represents an initial ‘bittern-friendly’ rice farm guideline. It will also improve the overall capacity of a rice

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crop to support additional biodiversity, such as Australian Reed Warblers that would not otherwise occur in rice crops.

A preliminary exploration of the sowing type indicates a strong preference by bitterns for aerially sown crops. The reasons for this are likely relate to water management and the scattered configuration of emerging rice plants, as drill-sown crops are managed with one or more dry periods to reduce damage by ducks and the rice plants emerge in rows, but this requires further investigation.

A preliminary analysis of the weed data from within crops and on banks indicates that there was no clear relationship with the extent of weeds and the presence of bitterns. Bitterns were regularly recorded in rice crops with weeds, such as Barnyard Grass (Echinochloa) and Dirty Dora (Cyperus difformis), but they were also regularly recorded in ‘clean’ rice crops without weeds. In Italy, the most important determinants of rice-crop use by Eurasian Bitterns were taller rice plants, more vegetated field banks, more weeds, a larger surface and closer proximity to remaining natural wetlands, but the significance of these factors varied during the season (Longoni et al. 2011).

Time constraints have prevented any analysis of the influence of pesticide and herbicide regimes on the use of rice crops by bitterns. None of the sites where bitterns were recorded were organic rice crops and the application of herbicide and pesticide regimes varies little so if there is an effect, it is likely to be minor, though this also requires further investigation.

No links with other crops, such as corn, or agricultural infrastructure were found.

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Other Fauna A total of 42 species of waterbird was recorded at the 63 sites during the 1-hour bittern surveys. The most common species were the White-necked , White-faced Heron, Eastern Great Egret, Australian White Ibis, Straw-necked Ibis and Black-tailed Native-hen, all of which were often found in rice crops with bitterns. Several noteworthy waterbird species were found. At one site near Deniliquin, a pair of Brolgas was recorded. They had bred at the site and had two unfledged chicks with them. Several species of migratory shorebirds were recorded, including a group of 55 Sharp-tailed Sandpiper using the edges of one of the rice crop study sites near Griffith. Additional (non-waterbird) bird species, such as the Australian Magpie-lark, Common Starling and Galah were also frequently recorded.

The most noteworthy species found was the nationally endangered Australian Painted Snipe. A total of 44 birds were recorded across five sites, including three of the randomly selected sites for the separate Coleambally study, along with a site near Barham and a site near Swan Hill. A paper is being prepared highlighting the significance of this finding. The importance of rice crops to the Australian Painted Snipe has previously been unrecognised. The biodiversity value of Australian rice crops and the potential role of the rice industry in waterbird conservation are further emphasised by these records of the Australian Painted Snipe.

Large numbers of were recorded, involving at least five species, including the nationally vulnerable Southern Bell Frog. The most common was the Spotted Marsh Frog. Almost all records of Southern Bell Frog were from Coleambally, with several sites in the western part of the Murray accounting for the only additional records. Coleambally is already recognised as a stronghold for the Southern Bell Frog (Pyke and Muir 2008; Wassens 2008). They are a known prey item for the Australasian Bittern, with a study near Melbourne suggesting they are the primary prey when available (Menkhorst 2012), but their importance as prey to Australasian Bitterns in rice crops requires further investigation. The relatively large number of Southern Bell Frogs in Coleambally may directly or indirectly explain the concentration of bitterns there. The diet of the Australasian Bittern varies, but primarily consists of , frogs and crayfish (Marchant and Higgins 1990; Kushlan and Hancock 2005), all of which were frequently recorded in rice crops during the 2011–2012 season.

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Implications and Recommendations

• The 70 individual Australasian Bitterns confirmed during this study and the subsequent estimate of 500—1000 using rice crops in the Riverina during the 2012—13 growing season are very important findings. If these bitterns are breeding successfully and constitute a sustainable population, the results represent the discovery of the global stronghold for this endangered species. Conservation efforts for the Australasian Bittern should be reprioritised to focus on rice farms and rice farmers. The rice industry can seize the opportunity to take the lead on bittern conservation, embracing the responsibility and supporting its growers to adopt bittern-friendly rice-growing practices where practical, as they are identified. This could represent the elusive large scale marriage of food production and nature conservation in Australia

• A population monitoring program should be developed as soon as possible and a more accurate population estimate produced. The sites should be representative of each of the three rice-growing regions, with repeat and more intensive surveys at a subset of sites used to explore more accurate extrapolation of survey results. Ideally, the sites should be selected randomly and consultation with an ecological statistician should be used to determine a sufficient number and configuration for long term monitoring. One hour surveys in the late afternoon and early morning are recommended, beginning at the start of December

• The continued and expanded engagement of rice farmers to increase their awareness and appreciation of the plight of bitterns will be crucial in the uptake of bittern-friendly rice-growing practices. These practices need to be developed from further investigation so that willing farmers can tailor their rice-growing techniques to suit bitterns and provide habitat outside of the rice-growing season. Initial indications are that aerially sown rice planted early in the season, with sympathetic management of Cumbungi, should benefit bitterns. Outside of the rice-growing season, the management of bittern habitat in storage dams, channels and natural wetlands is also likely to be important and could incorporate the re-use of drainage water after harvest

• Additional research should focus on five areas: (1) the breeding ecology of bitterns in rice crops; (2) the diet and foraging ecology of bitterns in rice crops; (3) the movement patterns of birds after harvest and during winter; (4) identification of the rice-growing techniques that benefit bitterns most; and (5) the use of rice crops by the endangered

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Australian Painted Snipe and opportunities to merge monitoring and conservation programs for these species

• Explore commercial opportunities, such as a rice variety known as ‘Bittern’ and the inclusion of the species in the marketing of rice products

• Highlight the environmental benefits of rice production, notably the significant provision of habitat for threatened waterbird and frog species.

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References

BirdLife International 2012, Botaurus poiciloptilus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. . [Verified 19 February 2013].

Coleambally Irrigation 2012, Coleambally Irrigation Annual Compliance Report 2012. Coleambally Irrigation Cooperative Limited, Coleambally.

Cramp, S & Simmons, KEL. Eds 1977, The Birds of the Western Palearctic, Vol. I. Oxford University Press: London.

Disher, P 2000, Birds of the Barham District, Barham Landcare Group: Barham.

DOC 2013, Department of Conservation, New Zealand – Australasian Bittern/Matuku facts. Available at http://www.doc.govt.nz/conservation/native-animals/birds/wetland- birds/australasian-bittern-matuku/facts/ [Verified 5 May 2013].

Garnett, ST, and GM, Crowley 2000, The Action Plan for Australian Birds 2000, Environment Australia and Birds Australia: Canberra.

Garnett, ST, Szabo, JK, and Dutson, G 2010, The action plan for Australian Birds 2010, CSIRO Publishing: Melbourne.

Gilbert, G, Tyler, GA, Dunn, CJ, Ratcliffe, N, and Smith, KW 2007, The influence of habitat management on the breeding success of the Great Bittern Botaurus stellaris in Britain. Ibis 149, 53–66.

Hafner, H, Lansdown, RV, Kushlan, JA, Butler, RW, Custer, TW, Davidson, IJ, Erwin Michael, R, Hancock, JA, Lyles, AM, Maddock, M, Marion, L, Morales, G, Mundkur, T, Perennou, C, Pineau, O, Turner, D, Ulenaers, P, van Vessum, J, and Young, L 2000, Conservation of Herons. In Heron Conservation, Eds J. A. Kushlan and H. Hafner. pp. 343-375. Academic Press: London.

Heather, B, and Robertson, H 2000, The Field Guide to the Birds of New Zealand, Revised edn. Viking: Auckland.

Herring, MW, Robb, M, Bull, N, Silcocks, A & Gibbs, D, in press, Bitterns boom in rice: identification of the global hotspot for Australasian Bitterns Botaurus poiciloptilus.

Holden, R 2001, Bunyips: Australia’s folklore of fear, National Library of Australia, Canberra.

Kushlan, JA. and Hancock, JA 2005, The Herons, Oxford University Press, New York.

Longoni, V, Rubolini, D and Bogliani, G 2007, Delayed reproduction among Great Bittern Botaurus stellaris breeding in rice fields. Bird Study 54, 275–279.

Longoni, V, Rubolini, D, Ambrosni, R and Bogliani, G 2011, Habitat preferences of Eurasian Bitterns Botaurus stellaris booming in ricefields: implications for management. Ibis 153, 695– 706.

Marchant, S, and Higgins, PJ Eds 1990, Handbook of Australian, New Zealand and Antarctic Birds. Vol. 1: Ratites to Ducks, Oxford University Press, Melbourne.

Menkhorst, P 2012, The food and foraging rate of an Australasian Bittern. Australian Field Ornithology 29, 133-142.

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O’Donnell, CFJ 2011, Breeding of the Australasian Bittern Botaurus poiciloptilus in New Zealand. Emu 111, 197-201.

Ogle, CC and Cheyne, J 1981, The Wildlife and Wildlife Values of the Whangamarino Wetlands. Fauna Survey Report No. 28, Wellington: NZ Wildlife Service.

Pyke, GH and Muir, GW 2008, Rice-growing and conservation of the Southern Bell Frog Litoria raniformis in New South Wales, Australia. Australian Zoologist 34, 453-458.

RGA 2013, Rice Growers’ Association of Australia. http://www.rga.org.au [Verified 5 May 2013].

Rogers, D, Coleborn, C, Herring, M, Silcocks, A, Starr, S, and Tzaros, C 2005, Notes on management requirements for Painted Snipe at Hird and adjacent swamps. Unpublished report to Parks Victoria, Kerang.

SEWPaC 2011, Advice to the Minister for Sustainability, Environment, Water, Population and Communities from the Threatened Species Scientific Committee the Committee on Amendment to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 EPBC Act. Available at http://www.environment.gov.au/biodiversity/threatened/species/pubs/1001-listing-advice.pdf [Verified 19 February 2013].

SunRice 2013, SunRice Annual Reports 2002-2012. Available at http://www.SunRice.com.au/shareholders-growers/company-reports [Verified 5 May 2013].

Wassens, S 2008, Review of the past distribution and decline of the Southern Bell Frog Litoria raniformis in New South Wales. Australian Zoologist 34, 446-452.

Wetlands International 2006, Waterbird Population Estimates – Fourth Edition, Wetlands International, Wageningen, The Netherlands.

Whiteside, AJ 1989, The behaviour of bitterns and their use of habitat. Notornis 36, 89-95.

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Bitterns in rice By Matthew W. Herring, Neil Bull and Andrew Silcocks Pub. No. 14/007

The Australasian Bittern (Botaurus poiciloptilus) is an endangered waterbird known to use rice crops in the Riverina region of New South Wales. The relative importance and conservation value of these habitats for this species was previously unknown. Potentially, rice farmers can make a significant contribution to the conservation of Australia’s ‘Bunyip Bird’.

This report is targeted at the rice industry and organisations involved in the environmental management and ecological sustainability of rice farms, such as government departments and Landcare groups.

RIRDC is a partnership between government and industry to invest in R&D for more productive and sustainable rural industries. We invest in new and emerging rural industries, a suite of established rural industries and national rural issues.

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