Gulf breeding study

On this page Ozcranes looks at the Gulf Breeding Study, the first extensive survey on crane breeding success (% of pairs with surviving chicks of the year) in northern Australia. It involves annual surveys of Sarus Cranes breeding in the Gulf Plains, and Brolgas breeding in the same area. A team visits the Gulf for two weeks each year, counting cranes from car rooftops. They record single cranes, non-breeding flocks, pairs without young, and pairs with new young, noting their preferred habitats. Shed feathers are also collected and analysed to discover the foods eaten by cranes during the breeding period.

For an introduction to Sarus Crane breeding habitats, nests and eggs, and chick development see Ozcranes Sarus Crane FAQ 2». For Brolgas, see Ozcranes Brolga FAQ 2».


Background and key issues

Until 2017 knowledge of Australian Sarus Crane breeding habitats and success was limited to John Grant's pilot surveys in the Gulf» and annual surveys of young wintering with parents on the Atherton Tablelands». Brolga breeding studies were mostly concentrated in southeast Australia, with some work in the 1970s near Townsville (see Ozcranes Sarus Crane FAQ 2» and Brolga FAQ 2»). Both species were known to breed in the Gulf, but how they coexisted there, any differences in habitats and food, and measures of breeding success, were unknown.

Sarus in Gulf

Adult and juvenile Sarus Crane foraging in borrow pit, Gulf Plains (KS Gopi Sundar)

In 2016-7, KS Gopi Sundar worked with John Grant» to upscale John's one-person surveys using his car roof survey method», to a multi-catchment program covering both species in the Gulf. Joining them were colleagues Swati Kittur, Inka Veltheim and Elinor Scambler», and the team formed a partnership with Professor Michael McCarthy of Melbourne University and the Native Australian Animals Trust. Research Fellow Kate Brandis from UNSW completed the team, performing expert isotopic and other analyses of feathers to determine crane diets.

Gulf wetland

↑ Wetland near Normanton, Gulf Plains, Qld (KS Gopi Sundar)

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Results

The first year's results have been published (Sundar et al., Sympatric cranes in northern Australia: abundance, breeding success, habitat preference and diet, abstract available at the link). The paper shows different floodplains, habitats and food for Brolgas and Sarus Cranes, and very high rates of success, with timing correlated with rains. The 2017 survey found a staggering breeding success rate for Sarus Cranes of 60.3%, the highest recorded for Sarus anywhere. As with wintering cranes on the Tablelands, this rate varies from year to year, and conditions in 2017 were exceptionally good. Breeding success for Brolgas has not previously been reported: in 2017 in the Gulf it was 50%, higher than for Sarus overseas.

The two species prefer different nesting habitats. Sarus Cranes nest mostly in four riverine Eucalyptus-dominated regional ecosystems, and only 10% used open habitats. Brolgas preferred two non-wooded grassland regional ecosystems, but 32% shared Eucalyptus-dominated habitats with Sarus Cranes.

Preferred breeding territory habitats (Regional Ecosystems) for Gulf Brolgas and Sarus Cranes (source: Sundar et al. 2019, see links below. Graph courtesy S Kittur and KSG Sundar)

Preferred breeding territory habitats, Brolgas and Sarus Cranes

Nest habitats

Regional Ecosystems (REs) represented are (from left to right):
Grassland: 2.3.1; 2.3.4. Woodland: 2.3.9; 2.3.10; 2.3.11; and 2.3.21

Feather analysis gave novel insights into differences in diet between Brolgas and Sarus Cranes. Sarus fed more on C3 plants (including cool-climate grasses) and from a more limited range of trophic levels; Brolgas fed more on C4 plants including tubers and C4 grasses, with a wider range of dietary items. This suggests that the two species coexist in the same landscape by using somewhat different foods as well as differing nest habitats and floodplains. Crane conservation in the Gulf, especially for Sarus Cranes, will depend on continuity of varied habitats and flooded wetlands. Proposed irrigation schemes could threaten breeding habitats in the future.

Sarus Crane breeding maps

The study has massively increased knowledge of breeding success and habitats for Australian Sarus Cranes and northern Brolgas. The 2017 results for Sarus Cranes only, are shown on the maps below in comparison with the fragmentary information published pre-2017. (For more on the earlier sightings see Ozcranes Sarus FAQ2»). The 2018 and 2019 surveys (not yet published) further extend the known nesting areas and numbers.

TOP LEFT: Study area in northern Queensland, Australia
TOP RIGHT: Historical nesting sites, numbered 1 to 4 (references below)
BOTTOM: Sarus Crane breeding records, 2017 survey

Source: Sundar et al. 2019, see links below. Maps courtesy S Kittur and KSG Sundar

Sarus Crane nests map Sarus Crane map 2017

Historical references (Sites 1 to 4, map top right)

[1] GW Archibald & SR Swengel. 1987. ‘Comparative ecology and behavior of eastern Sarus Cranes and Brolgas in Australia’ Proceedings of the 1985 Crane Workshop, ed. JC Lewis: 107-116. (Download from Ozcranes Downloads»)
[2] LH Walkinshaw. 1973. Cranes of the world. New York, Winchester.
[3] H B Gill. 1969. First record of the Sarus Crane in Australia. Emu 69, 49-52
[4] Marchant and Higgins 1993, HANZAB Vol 2 (Nest Record Scheme)

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Paper

K. S. Gopi Sundar, John D. A. Grant, Inka Veltheim, Swati Kittur, Kate Brandis, Michael A. McCarthy and Elinor C. Scambler (2019) ‘Sympatric cranes in northern Australia: abundance, breeding success, habitat preference and diet’, Emu-Austral Ornithology, 119:1, 79-89, DOI: 10.1080/01584197.2018.1537673

Articles and links

Acknowledgements

The work was supported by funding provided by an anonymous donor in Australia and a grant provided by the School of BioSciences, University of Melbourne. Funding was coordinated by the University of Melbourne's Native Australian Animals Trust.

The paper was a collaborative output between the International Crane Foundation (USA), the Nature Conservation Foundation (India), and the University of Melbourne (Australia), in association with independent ecologists, crane researchers, and the University of New South Wales. We are greatly indebted to administrative support provided by P. Byron, B. Didrickson, G. van Houten, R. Kingsford, S. Prabhakar, and S. Ryall. The School for International Training, Cairns, especially T. Cummings, is thanked for donating equipment for the survey and other logistical support. We thank the Mark Wainwright Analytical Centre, University of New South Wales, for laboratory capabilities. For help with procuring rainfall data sets we thank C. Visintin. Authors contributed to work as indicated: project planning: KSGS, IV, JDAG, ECS, MAM, SK; fundraising: ECS, MAM, KSGS; fieldwork: JDAG, IV, SK, KSGS; isotopic analysis: KB; data analysis: KSGS, SK, KB; manuscript writing: KSGS leading, with all authors contributing.

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