Crane Count results, Atherton Tablelands

The Crane Count is a volunteer survey of Brolgas and Sarus Cranes, held annually by BirdLife Northern Queensland since 1997. It is the first systematic population count for Australian Sarus Cranes and the first for far north Queensland Brolgas. The Atherton Tablelands has the only known non-breeding concentration of Australian Sarus Cranes, and organisers search before the count to locate communal night roosts. On the survey date, teams of people visit these swamps and dams to count both Brolgas and Sarus Cranes flying in to roost, from afternoon until dark.

Count results to 2008 established the Atherton Tablelands Key Biodiversity Area» and recently, Crane Count data contributed to the global Crane Conservation Strategy» (Mirande & Harris 2019). For people, the Crane Count has become a highlight of the year where they connect with cranes, each other and the environment. More about the background to Tableland cranes and the Crane Count teams at work can be found on Ozcranes here».

This page outlines an important new paper in Australian Field Ornithology, with findings from the first 21 years of counts, 1997-2017. For news of ongoing Crane Counts visit BirdLife Northern Queensland or contact the Coordinator. For enquiries specifically related to the paper on 21-year Count results, please contact Elinor Scambler.

CITATION: Elinor C Scambler, Timothy D Nevard, Graham N Harrington, E Ceinwen Edwards, Virginia Simmonds, Donald C Franklin. 2020. Numbers, distribution and behaviour of Australian Sarus Cranes Antigone antigone gillae and Brolgas A. rubicunda at wintering roosts on the Atherton Tablelands, far north Queensland, Australia. Australian Field Ornithology 37: 87-99.


Numbers

Survey results 1997 to 2017 show that the Tablelands is internationally significant for both species in the non-breeding season, particularly Sarus Cranes which are globally Vulnerable». The study has produced the first systematic minimum population estimate for Australian Sarus Cranes of 3,255, 19.5% of the estimated global population [1]. Over 3,460 Brolgas have wintered on the Tablelands, some 4.9% of the global population [1]. Annual crane numbers overall are very variable, possibly due to resource factors affecting migration numbers and periods, and to variations in recruitment and survival in the source populations.

[1] The estimated global population of Sarus Cranes is 13550 to 20650, of which an estimated 5000-10000 are in Australia. The estimated total population of Brolgas is 50000 to 100,000 - see also the FAQs for Brolga and Sarus, links at top of Sidebar

Mareeba Wetlands

↑ Brolgas and Sarus mingling at roost, Mareeba Wetlands (now Tropical Wetlands SER, Forever Wild), Atherton Tablelands, Queensland (Tim Nevard). Internationally, such mingling at mixed-species wintering roosts is rare

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Sympatry and ‘mingling’

Apart from the globally significant numbers of both species, the study is also of international interest because it's unusual for two such closely-related crane species to be sympatric (occupy the same areas). We would expect Brolgas and Sarus Cranes to use the landscape and resources in different ways, to achieve this. The Crane Count results show that Sarus roosts are strongly concentrated in the Key Biodiversity Area. However many roosts are shared, especially at Bromfield Swamp and sites outside the KBA in the Brolga-dominated north-west and south-west Tablelands. At shared roosts – except at General Plains Swamp (image below) – family groups of Sarus mingle with groups of Brolgas, a very unusual situation at mixed-species wintering crane roosts. This is also an apparent behavioural change since early observations on the Tablelands (more on Ozcranes here» and here»). There are even a few mixed species flocks flying in. As long suspected by Crane Counters, time of arrival analysis shows that Sarus Cranes arrive at roosts much later on average than Brolgas. The reasons are not clear, but Sarus may feed further away from roosts [2] and Brolgas may prefer food sources to be found in wetland sites, so arrive early to feed. The paper recommends further research into these behaviours, and also that future counts at all sites begin at least an hour before sunset. This will help future analyses determine if later arrival by Sarus Cranes still applies, or if behaviour has changed.

[2] Nevard Timothy D., Franklin Donald C., Leiper Ian, Archibald George, Garnett Stephen T. 2019. Agriculture, brolgas and Australian sarus cranes on the Atherton Tablelands, Australia. Pacific Conservation Biology 25: 377-385.

Unidentified cranes and recommendations

Many cranes arrive after sunset when light is failing, and every year many cannot be identified to species. This particularly affects data for Sarus Cranes (which as above, arrive later). No trends were detected in the study to 2017, but analysis was confounded by the high annual variation in numbers, variable numbers of unidentified birds, and change of month for the count after 13 years. Counts are now held in a consistent month (September). Use of night optics could possibly increase identification rates after sunset and improve trend detection.

The paper includes a method which can be used (with caveats) to improve population estimates by taking account of unidentified cranes, to support for example, monitoring in the Atherton Tablelands Key Biodiversity Area».

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↓ General Plains Swamp, Innot Hot Springs, Queensland. A major Brolga roost in most years, with 1 to (rarely) 100+ Sarus Cranes (Sandy Carroll).

General Plains SwampBromfield Swamp

↑ Bromfield Swamp, Malanda (Elinor Scambler). A mixed species roost with long term significant numbers of Sarus Cranes.

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Acknowledgements

The authors thank the hundreds of BirdLife members and supporters and the Atherton Tablelands community who have participated since 1997. We are very grateful to all the landowners who allowed access to their properties. No external funding was received.

Count organisers were: Elinor Scambler 1997-2008; Alan Gillanders 2009; Graham Harrington and Virginia Simmonds 2010-2015; David Merrall 2016- (and current). Ceinwen Edwards organised sites at Kaban-Tumoulin and Innot Hot Springs from 2004- and 2012-. Elinor Scambler founded the project as Birds Australia Atherton Tablelands activities organiser in 1997, the far-sighted Executive who approved and supported the Crane Count from its inception were: Graham Harrington (Convenor); Lindsay Fisher (Secretary); and Sue Clegg (Treasurer).

Articles and links

On Ozcranes

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