Knowledge Gaps 2

On this page we cover some longstanding questions about Australian Sarus Cranes being addressed by current studies, and others which are major research priorities.

A number of other ‘unknowns’ are covered in Ozcranes Introduction» to Australian cranes, and the FAQ pages for Brolga and Sarus (all links are in the Site Map»).


Sarus arrival

When Sarus were first formally recorded in Australia in 1966 debate began about their likely time as residents. The main argument favouring recent (say 1950s) arrival is that such a different bird would have been noticed sooner. In favour of a longer term, we have –

Von Sturmer's transcription of Aurukun names for Brolga and Red-legged Brolga [1].

Text

Further genetic work, including material from the extinct Philippines population, may progress this aspect further.

[1] Beruldsen, GR. 1997. Is the Sarus Crane under threat in Australia? Sunbird 27, pp. 72-78. For other references see Gaps 1».

Sarus increasing?

Australia's supposedly increasing population of Sarus Cranes is one of the popular but unevidenced ‘facts’ mentioned in the introduction to Knowledge Gaps 1. It was stated in HANZAB2, but Beruldsen [1 above] suggested instead, more Sarus were spending the Dry non-breeding season in more conspicuous places. The Action Plan for Australian Birds 2000 rated the population as stable, and ‘may be increasing’. An increase does not seem to be supported by molecular studies, but if an increase has occurred it may have plateaued. A 12-year study showed no trend in Dry season counts of a (presumed) significant part of the population. However, researchers working in the wider region (J Grant, T Nevard) consider that most Sarus probably spend the non-breeding season in and around the Gulf breeding areas, so have never been counted. Dr John Grant has shown a low but consistent mean annual recruitment rate for the same population over that period.

Hybrids

Renowned crane researcher Dr George Archibald observed, photographed and collected a ‘Sarolga’, as he later named the Brolga-Sarus hybrid, on the Atherton Tablelands in 1972. After 1972 there were (infrequent) observations of apparent wild hybrids, based on –

These field observations were not conclusive however, as Brolga and Sarus are closely related. Some features observed in the field may be primitive (shared due to a common ancestor), derived (evolved) or convergent (similar in form and function, but not related). Tim Nevard's PhD study into Sarus-Brolga interactions and hybridisation, including genetic analysis of blood and feather samples, is well advanced and results when available will create wide interest. For study description and field reports see Tim Nevard's page» in Ozcranes Research. Dr Archibald's paper ‘Introducing the Sarolga’ can be downloaded from Ozcranes Downloads».

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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. John Grant has documented stages of maturation from features of first year young still with their parents, to later stages of maturity when the young progressively develop full colours on head, neck, and legs. However the time taken to reach the different stages of maturity can't be fully known without marked birds. This complicates (at least) population monitoring of older immatures, determining age of first pair-formation and field observation of possible hybrids.

Habitat

BreedingThe only intensive nesting study in Australia [2] found Sarus 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. Incidental observations [1 above, 3] confirm Sarus choose swampy melaleuca woodlands and smaller wetlands on treed ridges. John Grant is continuing studies in the Gulf of Carpentaria. In the Dry season, some Sarus Crane pairs roost at scattered waterholes along sandy watercourses on Cape York Peninsula (see sidebar image), it's uncertain if they breed close by or disperse from the known Gulf breeding area. Indian Sarus show high nest site fidelity [4] and may retun to breed near the natal site many years after maturity, if this applies in Australia then competition for favoured nest habitat is increased. Further work is needed to –

[2] 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.(download from Ozcranes Downloads»).
[3] LH Walkinshaw. 1973. Cranes of the world. New York, Winchester.
[4] A Mukherjee et al. 2000. Nest and eggs of sarus crane (Grus antigone antigone Linn.). Zoos Print Journal 15(12): 375-385.

FlockingAs 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. More detailed information on characteristics of habitats used by either or both species is needed to consider potential conflict or exclusion between them, and whether land use changes might advantage one species over the other. This knowledge gap is a major focus of Tim Nevard's PhD study».

MovementsMarked birds, and especially birds fitted with tracking devices, reveal far more about habitat use, migration pathways, and breeding sites, than can be achieved by observational studies in isolation, as Inka Veltheim's PhD study on southern Brolgas has shown. It is still unknown whether Sarus wintering on the Tablelands do breed in the Gulf of Carpentaria. The first attempt to fit a young Australian Sarus with a transmitter is described in John Grant's article ‘Bird in the Hand’ (read on Ozcranes here). Tim Nevard» has banded five Sarus as part of his PhD study. This is a major area for future new work with Austalian Sarus.

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