North Queensland Crane Counts 2

Crane Counts 2 is an Ozcranes Research Report from a conference presentation by Elinor Scambler in 2005. The talk began with a run-through of what is known, and not known, about Sarus Cranes in Australia, then a list of controversial issues (‘Myths, legends and interesting hypotheses’). The talk then focussed on the Atherton Tablelands area with results from counts to 2004, the first systematic (non-breeding) population estimate for Sarus Cranes in Australia.

The surveys are a project of BirdLife Northern Queensland and have now spanned 20 years. Analysis and write-up are in progress, see Crane Counts 1» for details and contacts. The annual Crane Count was a fully volunteer activity. Thankyou to the many landowners who allowed access to their properties each year, and congratulations to the hundreds of BirdLife Australia members, others Queenslanders and visitors who contributed.


by Elinor Scambler

Title Calculating Cranes: The first 8 years of a long-term community study in north Queensland

Abstract Each October, over 100 north Queenslanders from Townsville to the Tablelands and beyond count Brolgas and Sarus Cranes as they fly in to wetland night roosts. Since 1997, this fully volunteer Birds Australia NQ Group project has confirmed the predominance of Sarus Cranes on the wetter Tablelands and is producing valuable data on crane numbers, pre-roosting movement patterns and roost habitat in north Queensland. The annual Count and related activities have increased knowledge and interest in crane ecology and conservation in the region.

Crane Count team Sarus Crane flock in twilight

From 1997, north Queensland Sarus Cranes & Brolgas flying in to roost were counted by community teams each October. Flocks ranged from 2-3 birds to over 70 (David Stowe).

Crane count team image courtesy Eleanor Duignan

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Full summary

The origins, population and ecology of Australian Sarus Cranes are not well-known. From just a few birds in 1967, the Sarus Crane dry season (non-breeding, or flocking) population on the Atherton Tableland has increased to become the only known major concentration of non-breeding Australian Sarus. Since 1997, BA-NQG and community volunteers have counted Sarus Cranes and Brolgas flying in to roost, on one night each October, at sites from Townsville north to Mareeba and west to Mt Garnet.

Some questions, and some preliminary answers:

Do Sarus Cranes consistently outnumber Brolgas in Atherton Tableland dry season flocks?
Yes, overwhelmingly. Historical records are now being collected and examined for clues on when the Tableland species balance changed: Brolgas probably still predominated in 1983.
Where do the two species co-exist in winter, with mainly Brolgas in flocks?
On the drier Tableland periphery eg Mareeba, and the Upper Herbert, where the number of Sarus is always much less than Brolgas, but highly variable. This may be due to environmental factors or differential migration timing between years, particularly in the Upper Herbert (a presumed ‘staging’ area for migrating Gulf-breeding cranes).
Where are Sarus rarely found?
In the Lower Herbert and Townsville area, where there are major roosts with Brolgas only.
How many Australian Sarus Cranes are there?
October counts of the Tableland and its hinterland only, show a minimum number of Sarus Cranes of about 1700, ranging from 1600 to 3000. These are ‘landed’ totals. Further analysis of flock movements with GIS is likely, in most years, to identify additional (‘lost’) birds which flew over a roost but were not counted elsewhere. Although preliminary, this study gives the first minimum population estimate for Sarus Cranes in Australia, from systematic counts. A number of possible reasons for year-to-year variations will be presented.
Are they increasing?
Commentators often infer an overall Sarus Crane population increase from the observed increase of wintering Sarus on the Tableland, but (albeit with only 8 years of localised data) there is no evidence for this. A major advance towards better population estimates, variations and trends, would be to combine the October roost count with a simultaneous aerial count of more scattered cranes in Gulf and CYP wetlands.

Brief comments were also presented on roost site characteristics, land use and current conservation issues affecting cranes in far north Queensland.

Notes:

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Q & A from the discussion after talk

What's the situation with the CYP Sarus Cranes?

(Speaker (ES) had stated the only confirmed breeding area is in the Gulf of Carpentaria). ES: The published Cape York records so far are of Sarus Cranes with dependent flying young, after the breeding season, so don't tell us where the nest site was. It may have been in the Gulf, or on the western Cape or the Lakefield area. That's not to say there isn't breeding on the Cape, just that I haven't found records yet. I've set up a data base and will be appealing for input.

Comment from questioner: It's so difficult to get access there in the Wet Season.

ES: Absolutely, and Dry Season records of Sarus Cranes on the Cape are not usually detailed either. Most are 2-4 birds, small family groups feeding during the day. No-one has reported a major winter flocking roost, like we count on the Atherton Tableland, the closest so far is a private dam near Lakeland Downs. There's no certainly no evidence the wintering population we count on the Tableland and environs covers all or even most, of Australia's Sarus Cranes, eg others may be widely scattered including on the Cape.

Do Sarus Cranes feed on sugar cane land?

ES: John Grant has been studying feeding habitat on the Tableland. Cranes are most often found on maize stubble; then pasture including with cattle, if short not overgrown; then finally, cane trash. So they will feed on cane land but seem to prefer elsewhere. I'm not aware of information on what foods they're using on those sites compared with what is available there. When the annual Crane Counts started in 1997, one issue raised was whether the increase of sugar cane cropping on the Tableland would disadvantage cranes. With no detected change in numbers over the 8 survey years so far, this seems not to be the case. That said, land planted to cane decreased for several years, but current assistance packages for the industry and higher world prices may change this again.

What habitats were Sarus Cranes using before clearing and agriculture in north Queensland?

(Speaker had (1) confirmed significance of mainly cleared agricultural land on Tableland for wintering population; and (2) explained that wetlands used by Sarus Cranes for breeding and winter roost sites are kept clear of dense vegetation by cyclical rise and fall of water, grazing and/or fire). ES: I've been thinking about that. Before about 1900 there would have been few suitable sites on the Tablelands, especially in the wetter, inner zone, which now hosts such a significant winter population. But presumably before pasture grasses and weeds were introduced, parts of the Gulf and Cape could have been maintained as crane habitat by the seasonal rise and fall of water and the historical burning regime. (Addition from audience: especially on Western Cape York).


About the author Elinor Scambler (aka cranesnorth) studies cranes and also birds in rainforest revegetation projects, and is the northern Australia representative for the Australian Crane Network. She is one of four Australian members of the Crane Specialist Group»


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