Diurnal foraging in short pasture by the Endangered Australasian Bittern (Botaurus poiciloptilus) on Kangaroo Island, Australia

Abstract

The Australasian Bittern (Botaurus poiciloptilus) is a globally endangered species that has undergone a decline in population associated with loss of wetlands and changes to hydrology. Australasian Bitterns typically utilise wetlands composed of reeds, sedges, rushes and other fringing or emergent vegetation. Here, I document the use of short open pasture and shallow ephemeral wetland with no fringing or emergent vegetation, on Kangaroo Island, South Australia, during the day. The observation provides further evidence that the Australasian Bitterns forage diurnally, especially in winter. This is only the fourth record of this species for Kangaroo Island, and reasons for this paucity of records are explored in light of recent research suggesting movement from the species’ stronghold in the Riverina of the Murray-Darling Basin to coastal wetlands.

Key words: Australasian Bittern, diurnal feeding, foraging habitat, Kangaroo Island, vagrant.

Introduction

The Australasian Bittern (Botaurus poiciloptilus) occurs in south-eastern mainland Australia, south-western Australia, New Zealand and New Caledonia. The species is globally Endangered (BirdLife International 2016BirdLife International. 2016. Australasian Bittern Botaurus poiciloptilus. The IUCN Red List of Threatened Species 2016: e.T22697353A93610014. [online]. Accessed 25 June 2022.), endangered in Australia (Commonwealth of Australia 2019Commonwealth of Australia. 2019. Draft national recovery plan for the Australasian Bittern. Department of Energy and the Environment, Canberra, Australia., Threatened Species Scientific Committee 2019Threatened Species Scientific Committee. 2019. Conservation advice Botaurus poiciloptilus Australasian Bittern. Threatened Species Scientific Committee, Canberra, Australia. [online]. Accessed 25 June 2022., Herring et al. 2021Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia.) and listed endangered or critically endangered in most of the Australian mainland states in which it occurs. In Australia, the Australasian Bittern has undergone population declines attributed to draining of and changes of hydrology to wetlands in the species’ stronghold of the Murray-Darling Basin (Buchanan 2009Buchanan, K. L. 2009. Wetland conservation in the Murray-Darling Basin — is it going down the drain? Emu - Austral Ornithology 109: i-iv., Maddock 2011Maddock, M. 2011. The status of herons and their wetland habitat in southeastern Australia, 2000-2010. Journal of Heron Biology and Conservation 1: 7. [online]., Herring et al. 2021Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia.).

Recent research is revealing new insights into habitat use (e.g., ricefields) and movements (e.g., Herring et al. 2019Herring, M. W., W. Robinson, K. K. Zander and S. T. Garnett. 2019. Rice fields support the global stronghold for an endangered waterbird. Agriculture, Ecosystems and Environment 284: 106599.). As such, documenting new information on range, habitat and behaviour is important. Here, I describe observations on the fourth record of this species on Kangaroo Island, South Australia, habitat use and activity, and explore reasons for the paucity of records on the Island in light of new research on the species’ movements.

Observations and Discussion

An Australasian Bittern was seen in an open paddock of damp short pasture grass grazed by sheep at ~13:00 hr off Cape Willougby Road, Cuttlefish Bay, Kangaroo Island (35° 44' 13" S, 137° 59' 48" E), on 13 August 2007. At first it was standing stationary in a resting position (sensu Whiteside 1989Whiteside, A. J. 1989. The behaviour of bitterns and their use of habitat. Notornis 36: 89-95.) but gradually begun moving its head upwards (Fig. 1). It then slowly walked approximately 20 m to the edge of a shallow ephemeral wetland within the paddock – a wetland with no fringing (other than grazed pasture grass) or emergent vegetation – where it assumed an alarm posture with head pointed diagonally upward (Fig. 2), before flying towards a thicket of Scarlet Bottlebrush (Callistemon rugulosus) approximately 80 m away (Fig. 3). The observations lasted approximately 2 mins.

The Australasian Bittern is considered to be a vagrant on Kangaroo Island (Baxter 1995Baxter, C. 1995. An annotated list of the birds of Kangaroo Island (revised edition). South Australia National Parks and Wildlife Service, Adelaide, Australia., 2015Baxter, C. 2015. Birds of Kangaroo Island: A photographic field guide. ATF Press, Adelaide, Australia., Robinson and Armstrong 1999Robinson, A. C. and D. M. Armstrong (eds.). 1999. A biological survey of Kangaroo Island, South Australia, 1989 and 1990. Heritage and Biodiversity Section, Department for Environment, Heritage and Aboriginal Affairs, South Australia, Australia., Gillam and Urban 2014Gillam, S. and R. Urban. 2014. Regional species conservation assessment project, phase 1 report: regional species status assessments, Kangaroo Island NRM Region. Department of Environment, Water and Natural Resources, South Australia, Australia.) and most distribution maps do not include Kangaroo Island in its distribution (e.g., Marchant and Higgins 1990Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia., McKilligan 2005McKilligan, N. 2005. Herons, egrets and bitterns: their biology and conservation in Australia. CSIRO Publishing, Melbourne, Australia., Herring et al. 2021Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia., eBird 2022eBird. 2022. Australasian Bittern Botaurus poiciloptilus. [online]. Accessed 25 June 2022.) although the Fleurieu Peninsula, the nearest mainland point, typically is included (Fig. 4).

Kangaroo Island has been subject to multiple bird surveys and compilations of bird lists and distributions (Baxter 1995Baxter, C. 1995. An annotated list of the birds of Kangaroo Island (revised edition). South Australia National Parks and Wildlife Service, Adelaide, Australia., 2015Baxter, C. 2015. Birds of Kangaroo Island: A photographic field guide. ATF Press, Adelaide, Australia., Paton et al. 2002Paton, D. C., J. A. Gates and L. P. Pedler. 2002. Birds. Pages 88-110 in Natural History of Kangaroo Island, 2nd edition. (M. Davies, C. R. Twidale and M. J. Tyler, eds.). Royal Society of South Australia Inc, Adelaide, Australia., Boulton et al. 2020Boulton, R., T. Hunt, L. Ireland and J. Thomas. 2020. Kangaroo Island rapid bird assessments, February 2020. BirdLife Australia, Melbourne, Australia.). The observations described above represent the fourth record of Australasian Bittern on Kangaroo Island (Baxter 2015Baxter, C. 2015. Birds of Kangaroo Island: A photographic field guide. ATF Press, Adelaide, Australia., Birds SA 2020Birds SA. 2020. Australasian Bittern Botaurus poiciloptilus [South Australian distribution map 20/02/2020]. [online]. Accessed 25 June 2022.).

Baxter (2015)Baxter, C. 2015. Birds of Kangaroo Island: A photographic field guide. ATF Press, Adelaide, Australia. documented previous occurrences on Kangaroo Island: “Rare; 4 observations; a specimen collected from Rocky River, FCNP [Flinders Chase National Park], Apr 1940 (SAM B22204); one at Chapman River estuary, Dudley Peninsula, Nov 1945 (possible misidentification of juvenile Nankeen Night Heron; paperbark-fringed estuary at this location supports a small breeding night heron colony); one in Pale Rush at Lake Kitty, near Stunsail Boom mouth, 30 June 1986; one photographed in open paddock with pocket of flooded Scarlet Bottlebrush near Cuttlefish Bay, Dudley Peninsular, 13 Aug 2007” (p. 152). The last observations were my observations described in this paper and provided earlier to Baxter (2015)Baxter, C. 2015. Birds of Kangaroo Island: A photographic field guide. ATF Press, Adelaide, Australia..

In Australia, the Australasian Bittern occurs mainly in freshwater wetlands where it favours permanent and seasonal wetlands with tall dense vegetation, particularly those dominated by sedges, rushes and reeds (e.g., Phragmites, Cyperus, Eleocharis, Juncus, Typha, Baumea, Bolboschoenus) or cutting grass (Gahnia) from 0.5-3.5 m in height growing over a muddy or peaty substrate (Marchant and Higgins 1990Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia.). It rarely uses estuaries or tidal wetlands (Marchant and Higgins 1990Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia.) and, in more recent decades, uses rice fields (Herring et al. 2019Herring, M. W., W. Robinson, K. K. Zander and S. T. Garnett. 2019. Rice fields support the global stronghold for an endangered waterbird. Agriculture, Ecosystems and Environment 284: 106599.). The Australasian Bittern forages in still, shallow water up to 0.3 m deep, often at the edges of pools or waterways, or from platforms or mats of vegetation over deep water (Marchant and Higgins 1990Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia.). In south-western Western Australia, it also utilises swamps with shrubs (Melaleuca spp., Agonis spp.) (Pickering 2013Pickering, R. 2013. Australasian Bittern in Southwest Australia. BirdLife Australia, Melbourne, Australia. [online]. Accessed 25 June 2022.; R. P. Jaensch, unpublished, in Herring et al. 2021Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia.).

In a comprehensive review of the species in Australia and New Zealand, Marchant and Higgins (1990)Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia. did not list open, short pasture as a habitat type. However, more recently, Herring et al. (2021)Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia. note that “on occasion, they can feed away from water bodies such as in grassland or crop stubble, particularly during rodent plagues (A. Silcocks unpublished)” (p. 223), while Martínez-Vilalta et al. (2020a)Martínez-Vilalta, A., A. Motis and G. M. Kirwan. 2020a. Australasian Bittern (Botaurus poiciloptilus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, eds.). Cornell Lab of Ornithology, Ithaca, New York, U.S.A. [online]. Accessed 25 June 2022. state “only occasionally in open areas” but provide no further details. Rees (2015) Rees, G. 2015. Australasian bittern | Matuku-hūrepo. Adult walking through pasture. Eastern Southland, August 2015. New Zealand Birds. [online]. Accessed 25 June 2022.photographed an Australasian Bittern walking through short pasture in New Zealand.

Although the species is suggested to mostly feed at night, dusk or dawn (Marchant and Higgins 1990Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia., McKilligan 2005McKilligan, N. 2005. Herons, egrets and bitterns: their biology and conservation in Australia. CSIRO Publishing, Melbourne, Australia., Martínez-Vilalta et al. 2020aMartínez-Vilalta, A., A. Motis and G. M. Kirwan. 2020a. Australasian Bittern (Botaurus poiciloptilus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, eds.). Cornell Lab of Ornithology, Ithaca, New York, U.S.A. [online]. Accessed 25 June 2022.), it is increasingly being shown to feed by day, especially in winter (Whiteside 1989Whiteside, A. J. 1989. The behaviour of bitterns and their use of habitat. Notornis 36: 89-95., Menkhorst and Silcocks 2004Menkhorst, P. and A. Silcocks. 2004. Observations of Australasian Bittern eating small mammals. Australian Field Ornithology 21: 37-39., Menkhorst 2012Menkhorst, P. 2012. The food and foraging rate of an Australasian Bittern. Australian Field Ornithology 29: 133-142., Gitsham 2018Gitsham, J. 2018. The observation and photographic documentation of an Australasian Bittern catching and consuming a small mammal. South Australian Ornithologist 42: 71-74., this paper). Similarly, Gu et al. (2019)Gu, D., Y. Chai, Y. Gu, J. Hou, L. Cao and A. D. Fox. 2019. Annual migration routes, stopover patterns and diurnal activity of Eurasian Bitterns Botaurus stellaris wintering in China. Bird Study 66: 43-52. found Eurasian Bitterns (Botaurus stellaris) to be largely diurnal in their activity during winter in China, despite being considered to be mostly crepuscular and nocturnal by others (e.g., Martínez-Vilalta et al. 2020bMartínez-Vilalta, A., A. Motis and G. M. Kirwan. 2020b. Great Bittern (Botaurus stellaris), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie and E. de Juana, eds.). Cornell Lab of Ornithology, Ithaca, New York, U.S.A. [online]. Accessed 25 June 2022.).

New insights from satellite tagged birds suggest Australasian Bitterns disperse from the Murray-Darling Basin’s Riverina district to coastal wetlands in South Australia, Victoria and New South Wales (Herring et al. 2016Herring, M., I. Veltheim and A. Silcocks. 2016. Robbie’s gone a roaming. Australian Birdlife 5(3): 26-31., 2019Herring, M. W., W. Robinson, K. K. Zander and S. T. Garnett. 2019. Rice fields support the global stronghold for an endangered waterbird. Agriculture, Ecosystems and Environment 284: 106599., 2021Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia.), typically in winter. Three of the four records from Kangaroo Island are from winter (including the observation described in this paper). The paucity of records of Australasian Bitterns on Kangaroo Island raises a number of interesting questions. Kangaroo Island is Australia’s third largest island at 440,000 hectares and contains intact and high quality wetlands (Seaman 2002Seaman, R. L. 2002. Wetland inventory of Kangaroo Island: An assessment of selected inland wetlands of Kangaroo Island, South Australia. Department for Environment and Heritage, Adelaide, Australia.). At its closest point, Kangaroo Island is 13.5 km from the Fleurieu Peninsula on mainland Australia. Is this sea barrier an impediment to more regular movements or is the species simply under-reported on Kangaroo Island?

Herring et al. (2019)Herring, M. W., W. Robinson, K. K. Zander and S. T. Garnett. 2019. Rice fields support the global stronghold for an endangered waterbird. Agriculture, Ecosystems and Environment 284: 106599. suggested the population of Australasian Bitterns in Tasmania “may also be supplemented by birds from the mainland, including from the Riverina. Although no crossing of Bass Strait has been documented, the species has been recorded on both Flinders and King Islands in Bass Strait (Green, 1969Green, R. H. 1969. The birds of Flinders Island. Records of the Queen Victoria Museum No. 34. Queen Victoria Museum, Launceston, Australia.; Green and McGarvie, 1971Green, R. H. and A. M. McGarvie. 1971. The birds of King Island. Records of the Queen Victoria Museum No. 40. Queen Victoria Museum, Launceston, Australia.; McGarvie and Templeton, 1974McGarvie A. M. and M. T. Templeton. 1974. Additions to the birds of King Island, Bass Strait. Emu 74: 91-96.), and the Eurasian Bittern is a regular long-distance migrant across marine barriers (Cramp and Simmons, 1977Cramp, S. and K. E. L. Simmons (eds.). 1977. The birds of the Western Palearctic. Volume 1. Ostrich to Ducks. Oxford University Press, Oxford, U.K.)” (p. 6). Martínez-Vilalta et al. (2020b)Martínez-Vilalta, A., A. Motis and G. M. Kirwan. 2020b. Great Bittern (Botaurus stellaris), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie and E. de Juana, eds.). Cornell Lab of Ornithology, Ithaca, New York, U.S.A. [online]. Accessed 25 June 2022. note a number of islands where the Eurasian Bittern occurs in the non-breeding season and individuals of this species move between the UK and continental Europe (Brown et al. 2012Brown, A., G. Gilbert and S. Wotton. 2012. Bitterns and bittern conservation in the UK. British Birds 105: 58-87.), while Gu et al. (2019)Gu, D., Y. Chai, Y. Gu, J. Hou, L. Cao and A. D. Fox. 2019. Annual migration routes, stopover patterns and diurnal activity of Eurasian Bitterns Botaurus stellaris wintering in China. Bird Study 66: 43-52. installed GPS/GSM loggers on Eurasian Bitterns in China and found they crossed Bohai Bay, a distance of approx. 440 km at its longest point. The extent to which the Australasian Bittern undertakes sea crossings across the Southern Ocean in winter is an area for further research.

Alternatively, Australasian Bitterns may occur on Kangaroo Island more often than reported. The island has a relatively small population (5,000 people) and much of the island is not accessible to birdwatchers (being private farming properties or remote and inaccessible protected areas). This, combined with their usually cryptic nature, may make Australasian Bitterns hard to detect. Grazing of the ephemeral wetland has likely reduced habitat suitability at this site, and probably others on the island, for this cover dependent species. Managing grazing in ways that enable emergent vegetation stands to develop could benefit habitat values for Australasian Bitterns on Kangaroo Island.

Acknowledgements

Thanks to Janelle Thomas and the late Chris Baxter for discussions on this observation, and to Chip Weseloh and two anonymous reviewers for helpful comments on a draft of this paper.

Literature Cited

Baxter, C. 1995. An annotated list of the birds of Kangaroo Island (revised edition). South Australia National Parks and Wildlife Service, Adelaide, Australia.

Baxter, C. 2015. Birds of Kangaroo Island: A photographic field guide. ATF Press, Adelaide, Australia.

BirdLife International. 2016. Australasian Bittern Botaurus poiciloptilus. The IUCN Red List of Threatened Species 2016: e.T22697353A93610014. [online]. Accessed 25 June 2022.

BirdLife International. 2022. Species factsheet: Australasian Bittern Botaurus poiciloptilus. [online]. Accessed 25 June 2022.

Birds SA. 2020. Australasian Bittern Botaurus poiciloptilus [South Australian distribution map 20/02/2020]. [online]. Accessed 25 June 2022.

Boulton, R., T. Hunt, L. Ireland and J. Thomas. 2020. Kangaroo Island rapid bird assessments, February 2020. BirdLife Australia, Melbourne, Australia.

Brown, A., G. Gilbert and S. Wotton. 2012. Bitterns and bittern conservation in the UK. British Birds 105: 58-87.

Buchanan, K. L. 2009. Wetland conservation in the Murray-Darling Basin — is it going down the drain? Emu - Austral Ornithology 109: i-iv.

Commonwealth of Australia. 2019. Draft national recovery plan for the Australasian Bittern. Department of Energy and the Environment, Canberra, Australia.

Cramp, S. and K. E. L. Simmons (eds.). 1977. The birds of the Western Palearctic. Volume 1. Ostrich to Ducks. Oxford University Press, Oxford, U.K.

eBird. 2022. Australasian Bittern Botaurus poiciloptilus. [online]. Accessed 25 June 2022.

Gillam, S. and R. Urban. 2014. Regional species conservation assessment project, phase 1 report: regional species status assessments, Kangaroo Island NRM Region. Department of Environment, Water and Natural Resources, South Australia, Australia.

Gitsham, J. 2018. The observation and photographic documentation of an Australasian Bittern catching and consuming a small mammal. South Australian Ornithologist 42: 71-74.

Green, R. H. 1969. The birds of Flinders Island. Records of the Queen Victoria Museum No. 34. Queen Victoria Museum, Launceston, Australia.

Green, R. H. and A. M. McGarvie. 1971. The birds of King Island. Records of the Queen Victoria Museum No. 40. Queen Victoria Museum, Launceston, Australia.

Gu, D., Y. Chai, Y. Gu, J. Hou, L. Cao and A. D. Fox. 2019. Annual migration routes, stopover patterns and diurnal activity of Eurasian Bitterns Botaurus stellaris wintering in China. Bird Study 66: 43-52.

Herring, M., I. Veltheim and A. Silcocks. 2016. Robbie’s gone a roaming. Australian Birdlife 5(3): 26-31.

Herring, M. W., W. Robinson, K. K. Zander and S. T. Garnett. 2019. Rice fields support the global stronghold for an endangered waterbird. Agriculture, Ecosystems and Environment 284: 106599.

Herring, M. W., P. Barratt, A. H. Burbidge, M. Carey, A. Clarke, S. Comer., B. Green, R. Pickering, C. Purnell, A. Silcocks, V. Stokes, E. Znidersic, R. P. Jaensch and S. T. Garnett. 2021. Australasian Bittern Botaurus poiciloptilus. Pages 222-224 in The Action Plan for Australian Birds 2020 (S. T. Garnett and G. B. Baker, eds.). CSIRO Publishing, Melbourne, Australia.

Maddock, M. 2011. The status of herons and their wetland habitat in southeastern Australia, 2000-2010. Journal of Heron Biology and Conservation 1: 7. [online].

Marchant, S. and P. J. Higgins (eds.) 1990. Handbook of Australian, New Zealand and Antarctic birds. Vol. 1: Ratites to Ducks. Oxford University Press, Melbourne, Australia.

Martínez-Vilalta, A., A. Motis and G. M. Kirwan. 2020a. Australasian Bittern (Botaurus poiciloptilus), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, eds.). Cornell Lab of Ornithology, Ithaca, New York, U.S.A. [online]. Accessed 25 June 2022.

Martínez-Vilalta, A., A. Motis and G. M. Kirwan. 2020b. Great Bittern (Botaurus stellaris), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie and E. de Juana, eds.). Cornell Lab of Ornithology, Ithaca, New York, U.S.A. [online]. Accessed 25 June 2022.

McKilligan, N. 2005. Herons, egrets and bitterns: their biology and conservation in Australia. CSIRO Publishing, Melbourne, Australia.

McGarvie A. M. and M. T. Templeton. 1974. Additions to the birds of King Island, Bass Strait. Emu 74: 91-96.

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

Menkhorst, P. and A. Silcocks. 2004. Observations of Australasian Bittern eating small mammals. Australian Field Ornithology 21: 37-39.

Paton, D. C., J. A. Gates and L. P. Pedler. 2002. Birds. Pages 88-110 in Natural History of Kangaroo Island, 2nd edition. (M. Davies, C. R. Twidale and M. J. Tyler, eds.). Royal Society of South Australia Inc, Adelaide, Australia.

Pickering, R. 2013. Australasian Bittern in Southwest Australia. BirdLife Australia, Melbourne, Australia. [online]. Accessed 25 June 2022.

Rees, G. 2015. Australasian bittern | Matuku-hūrepo. Adult walking through pasture. Eastern Southland, August 2015. New Zealand Birds. [online]. Accessed 25 June 2022.

Robinson, A. C. and D. M. Armstrong (eds.). 1999. A biological survey of Kangaroo Island, South Australia, 1989 and 1990. Heritage and Biodiversity Section, Department for Environment, Heritage and Aboriginal Affairs, South Australia, Australia.

Seaman, R. L. 2002. Wetland inventory of Kangaroo Island: An assessment of selected inland wetlands of Kangaroo Island, South Australia. Department for Environment and Heritage, Adelaide, Australia.

Threatened Species Scientific Committee. 2019. Conservation advice Botaurus poiciloptilus Australasian Bittern. Threatened Species Scientific Committee, Canberra, Australia. [online]. Accessed 25 June 2022.

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