Knowledge Gaps 2
On this page we canvass some interesting hypotheses about Australian Sarus Cranes still awaiting investigation. And even the common and better-studied Brolga has its mysteries: for example the New Guinea population is virtually unknown, and all Brolga studies in Australia have concentrated on threatened south-eastern populations.
Issues that are reasonably well-settled – but often not widely appreciated – are in Knowledge Gaps 1. More unknowns on numbers, movements, distribution and breeding are in Ozcranes Brolga and Sarus Crane FAQs.
Nesting & Development
No Australian Sarus nest has been followed from egg to flying young and there are no marked birds. Information like incubation time, first flight and first breeding comes from India, southeast Asia or captive birds. Features of first year young still with their parents are being documented but later stages of maturity when the young progressively develop full colours on head, neck, and legs are much harder to establish, without known-age birds. This complicates (at least) population monitoring of older immatures, determining age of first pair-formation and field observation of possible hybrids.
‘Sarolga’, Wrotham Park October 2012 (Tim Nevard)
When Sarus Cranes were identified in Australia in 1966 speculation began about interbreeding with Brolgas. In 1980, crane researcher and joint founder of the International Crane Foundation Dr George Archibald, presented a paper to the International Crane Symposium in Sapporo, Japan. In ‘Introducing the Sarolga’, he described Brolga-Sarus hybrid cranes seen on the Atherton Tablelands during his 1972 trip to Australia.
Reports of apparent wild hybrids are based on –
- Unusual head colouring/extent of colouring
- Unusual leg colouring
- Unusual combinations of head and leg colouring
- The above sometimes combined with unusual plumage
- Reports of Sarus Crane/Brolga ‘acting as a pair’
Some scientific literature has stated (on the above basis) that wild Brolgas and Sarus Cranes hybridise, but molecular studies have so far found no supporting evidence. More blood or feather samples for testing are a priority. Some birds may hybridise, or, as with initial assumptions that the Brolga and Sarus Crane were sister species, features observed in the field can be misleading. They may be primitive (shared due to a common ancestor), derived (evolved) or convergent (similar in form and function, but not related).
Tim Nevard has now commenced his PhD study into Sarus-Brolga interactions including hybridisation – see his study page» in Ozcranes Research.
← In the Dry Season, some Sarus Crane pairs roost at scattered waterholes along sandy watercourses on Cape York Peninsula (Elinor Scambler, CYP). The largest known wintering population concentrates on the inner (wetter) Atherton Tableland, while Brolgas occupy drier hinterlands
→ Typical Sarus Crane nest site habitat in the Gulf of Carpentaria, NW Qld. Brolgas nesting in the same area choose more open sites (John Grant)
As outlined in Sarus Crane FAQ3, Sarus have been observed using fewer habitats than Brolgas but records from areas with both species give no broad indicator of habitat choice based on ‘wetter’ vs. ‘drier’ environments. Without more detailed information on characteristics of habitats used by either or both species, it seems premature to be predicting conflict or exclusion between them, or whether land use changes will advantage one species over the other – Tim Nevard's study» will address habitat use in the non-breeding season.
One key Sarus habitat issue has been better documented. Australian Sarus seem very selective in choosing nest sites compared with Brolgas, and compared with Indian Sarus Cranes that breed successfully in open sites like flooded paddy rice fields. All the data so far sugggest they particularly choose swampy melaleuca woodlands and smaller wetlands on treed ridges, John Grant is continuing studies in the Gulf of Carpentaria. Further work is needed to –
- identify major nesting areas other than the Smithburne-Gilbert Fan Aggregation NW of Normanton & vicinity
- identify finer-grained habitat characteristics of nest site selection
- using Landsat imaging and GIS, estimate available potential nest habitat of this type
Archibald, GW & Swengel, SR. 1985. Comparative ecology and behaviour of Eastern Sarus Cranes and Brolgas in Australia Proceedings of the 1985 Crane Workshop, pp. 107-116.
Beruldsen, GR. 1997. Is the Sarus Crane under threat in Australia? Sunbird 27, pp. 72-78.
Borad, CK; Mukherjee, A & Parasharya, BM. 2001. Nest selection by the Indian Sarus Crane in the paddy crop agroecosystem. Biological Conservation 98, pp. 89-96.
Sarus Crane flock (David Stowe)
Ozcranes view (John Grant and Elinor Scambler) is that Sarus Crane conservation should be more seriously considered than for other ‘Least Concern’ species in Queensland including Brolga (see definitions below). This is based on concern that Sarus in Australia may have little resilience to significant change in essential habitat, or increased mortality events, due to (1) Almost no reliable information on population size, status, and life history parameters in Australia (2) Low recruitment rate (based on wintering population study, Grant 2005 and unpublished data); (3) Apparently stable wintering population (E Scambler unpublished data) (4) Apparently restricted selection of breeding habitat (see above) and (5) Land use changes affecting stability of winter roost sites.
Links and downloads:
- International: Sarus Crane is classified as Vulnerable due to population decline overseas – download Sarus Crane Fact Sheet from BirdLife International
- Australia is a signatory to international agreements on migratory waterbirds that include the Sarus Crane. As a result, potential impacts on Australian Sarus are considered in Environmental Impact Statements under federal legislation
- The Action Plan for Australian Birds 2000 classed Sarus as ‘Least Concern’, confirmed in the 2010 Plan. Ozcranes download: Sarus account, Action Plan 2000
- Queensland: most Australian Sarus and all known breeding sites are located in Queensland. Sarus are protected under the Nature Conservation Act but the Nature Conservation Regulations classify Sarus as ‘Least Concern’. So there is no impetus for environmental funding, and no special focus on Sarus with issues like powerline impact, wetland drainage, sustainable use controls on aboriginal hunting, and so on. (Note the comment from one advisor on the Fencing Whiteboard that potential wetland fencing impacts on Sarus Cranes are ‘not a sustainability issue’).
- Important Bird Areas (IBAs) were declared in 2009 for the Atherton Tablelands (main Sarus wintering area) and Gulf Plains (breeding area). Enter the IBA name at Birdata to view facts and maps.
- Modelling suggests potential climate change impacts for Sarus, download paper from Australian Policy Online