Secrets of the Sarus Crane

Part 3 of an article originally published in a special Wetlands edition of Wingspan, former membership magazine of Birds Australia (now BirdLife), Vol. 14:4 December 2004. The original text is reproduced by permission (edited for web by Ozcranes).

Researcher John Grant takes a midday break with Sarus Cranes on north Queensland's Atherton Tableland. As the cranes drink and display at the shallow edge of a large dam, he touches on controversial issues: potential competition and hybridisation in the wild with Brolgas, origins in mainland SE Asia or even the Philippines, and possible reasons why Sarus weren't officially identified in Australia until 1966.

Secrets of the Sarus Crane

By John Grant

Part 3: Invasion or expansion?

Although it is widely believed that the Sarus Crane has increased dramatically in Australia since the 1960s, data on its population dynamics are virtually non-existent. The apparent increase in numbers could reflect a range expansion as agriculture becaome more widespread after the Second World War, or as increased cattle grazing altered the landscape. Both of these activities may have modified habitats in ways that favour the crane. It has also been suggested that the Sarus Crane has increased to the detriment of the Brolga, though again good data are lacking. The Brolga may have declined locally as a result of land use changes, rather than through direct competition with the Sarus Crane.

As usual, there are a few Brolgas scattered among the Sarus Cranes here today – even at long range, if the light is good, the dark grey legs of the Brolga and its overall whiter plumage are distinctive. In the drier reaches of north Queensland, the Brolga becomes more numerous, dominating crane flocks in woodland country and croplands north and south of the tablelands.

I pause to take a better look at an unusually marked bird – it is grey-legged like a Brolga, with the bright yellow eye of that species (the Sarus Crane has a darker, reddish eye), but the red of the head is more extensive than on a typical Brolga, and the dark dewlap on the throat is barely present. Several birds show features intermediate between the two species, and this particular bird is one of the most convincing arguments I have yet seen that hybridisation cccurs in the wild. Captive hybridisation has produced fertile offspring, christenened ‘Sarolgas’ by George Archibald, inaugural president of the International Crane Foundation (ICF), who took birds of both species to the US for the ICF's first captive breeding programs in 1972. To date, however, the rate of hybridisation in the wild and the fate of the resulting young are undocumented – another potentially important area of study for the future.

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By noon, I have been able to find and survey a number of flocks, totalling almost 700 birds, and I break for lunch near Lake Tinaroo, the large impoundment that holds the irrigation water for most of the region's farmers. The lake also provides a midday drinking haunt for the cranes, some of which fly in as I watch. Later in the dry season, hundreds of cranes come to the water in the hottest part of the day, sometimes even sitting in the shallows to cool off. Some of the birds drinking today break into the spectacular dancing routines that are so much a part of crane lore. They leap high with wings spread, alternately bowing and trumpeting with up-stretched necks, tossing clumps of grass with their beaks and encouraging flockmates to join in their wild antics.

As I enjoy the performance my mind wanders to the biggest mystery of the Australian Sarus Crane – how long have these birds been on this continent? Were the first sightings in the 1960s merely a belated recognition of a bird that had been in the country for much longer, or were they the first records of a recently immigrant population? Some argue that the similarity of Brolgas and Sarus Cranes caused the latter to be overlooked by the early naturalists, while others remain sufficiently impressed by the skills of pioneering ornithologists to doubt this possibility. Many have regarded the question as finally answered by the genetic characteristics of Indochinese and Australian Sarus Cranes which indicate that these populations have not been in contact for many thousands of years.

However, another loose thread remains in the form of the now extirpated Philippine population of Sarus Cranes. These birds, to date genetically unstudied, disappeared from their range on the island of Luzon sometime after the l940s, presumably as post-war population growth and development rapidly changed the face of the landscape. Is it a coincidence that the Sarus Crane was first recorded in Australia soon afterwards? Some see the apparently rapid rise in numbers and occurrence of small numbers of hybrids as evidence favouring the recent colonisation hypothesis.

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«Back to Part 1 | Morning scene

«Back to Part 2 | From small beginnings

Next: Part 4 | A craterful of cranes»

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