Knowledge Gaps 1
Many often-repeated ‘facts’ about Australian Sarus Cranes are still interesting hypotheses waiting to be investigated. Some are apparently myths waiting to die, despite evidence to the contrary.
Here in Knowledge Gaps 1 we outline some issues on the way to being settled, and some myths whose time has come. Part 2 looks at key areas for future research including Brolga-Sarus hybrids and reasons to challenge the official conservation status of Australian Sarus.
Sub-species
In 1966 the ‘first’ Australian Sarus were classified as the SE Asian sub-species, sharpei. But in 1988 a new Australian sub-species gillae (sometimes spelt gilliae) was described in somewhat controversial circumstances in Canberra Bird Notes (13:4, Dec. 1988, pp.119&122), citing smaller size (using wing size as the example) and different plumage on ears and upper throat. Studies on mitochondrial DNA and recently nuclear DNA, show no support for distinguishing sub-species. The differences between all Sarus are regarded as clinal (gradual and continual across its range). The formal position in Australia still appears to be based on the 1988 publication. But given the complete reproductive isolation of Australian Sarus, some argue this gives the best focus for conservation efforts.
Schodde, R, Blackman, JG, & Haffenden, AT. 1988. New subspecies of Australian Birds. Canberra Bird Notes 13:4, pp. 119-122.
Krajewski, C & Wood, C. 1995. Mitochondrial DNA relationships within the Sarus Crane species group (Gruiformes: Gruidae). Emu 95, pp. 99-105.
Wood, C & Krajewski, C. 1996. Mitochondrial DNA sequence variation among the subspecies of Sarus Crane (Grus antigone). Auk 113, pp. 655-663. Download from SORA.
Beruldsen, GR. 1997. Is the Sarus Crane under threat in Australia? Sunbird 27, pp. 72-78.
Jones, KL. 2005. Genetic variation and structure in cranes: A comparison among species. PhD Dissertation. Download from ICF.
Jones, KL, Barzen, JA & Ashley, MV. 2005. Geographical partitioning of microsatellite variation in the sarus crane. Animal Conservation 8, pp. 1-8. Download (abstract only) from here.
Closest relatives
← White-naped Crane, the Brolga's closest relative (International Crane Foundation).
Based on plumage, morphometrics (measurements) and unison calls, Brolgas and Sarus Cranes were long assumed to be sister species – each other's closest relatives. But a series of genetic studies shows that while both join the White-naped Crane Grus vipio to form a close group within Grus, the White-naped is closest to the Brolga.
Krajewski, C. 1989. Phylogenetic relationships among cranes (Gruiformes: Gruidae) based on DNA hybridization. Auk 106, pp. 603-618. Download from SORA.
Krajewski, C & Fetzner, JW Jr. 1994. Phylogeny of cranes (Gruiformes: Gruidae) based on cytochrome-b DNA sequences. Auk 111, pp. 351-365. Download from SORA.
TOPSarus arrival
← Von Sturmer's transcription of Aurukun names for Brolga and Red-legged Brolga (Beruldsen 1997, Sunbird).
When Sarus were first officially 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 recorded sooner. In favour of a longer term, we have –
- Mitochondrial and nuclear DNA suggest a much longer period of breeding separation: up to 3,000 generations (>30,000 years) with low genetic diversity
- Time needed to evolve size and plumage differences (as reported in the 1988 Canberra Bird Notes)
- Language terms (Aboriginal and non-Aboriginal), presumably originating before 1950s
- North Queensland resident stories (Aboriginal and non-Aboriginal) presumably predating 1950s
- ‘Late’ official record explained by lack of travel by ornithologists and/or Sarus, before WW2
Wild card In 2004 ornithologist John Grant suggested Australian Sarus could be the remnants of the Philippines population that disappeared around the 1940s. This interesting idea is consistent with long separation. It can be debated on the basis of biogeography but could only be disproved by DNA studies, yet to be done.
Sarus increasing?
← Counts and annual recruitment rates of Sarus Cranes wintering on the Atherton Tableland have remained stable for the last 8-10 years (David Stowe).
The Action Plan for Australian Birds 2000 stated that the population size for Australian Sarus is stable, while acknowledging the view of some (repeated also in HANZAB2) that it is increasing. Beruldsen (Sunbird 1997) suggested instead, more Sarus were spending the Dry (non-breeding season) in more conspicuous places. An increase does not seem to be supported by any molecular studies, but if an increase has occurred it has probably plateaued. At least for the last 9 years, there has been no trend in Dry season counts of a significant part of the population. As well, John Grant has shown a consistent, although low, mean annual recruitment rate for the same population over that period.
Next: Knowledge Gaps 2 | New challenges»
More.. The 1992 baseline for Brolga and Sarus knowedge gaps, many still unexplored, is in HANZAB2. Unknowns on questions like population numbers, movements, distribution and some aspects of breeding are in Ozcranes Brolga and Sarus Crane FAQs, with more on Sarus uncertainties in the Action Plan 2000.
