Breeding for Success

Dr John Grant has been studying Australian Sarus Cranes since 1997 amongst non-breeding dry season flocks on the Atherton Tablelands, and also in wet season breeding areas in the Gulf of Carpentaria. In 2005 he published the first and only formal scientific paper on Sarus breeding success» in Australia. In this Ozcranes Research report Dr K. S. Gopi Sundar, Director of Program SarusScape, explores John's work across the Atherton Tablelands and how it helps to understand the risks and survival prospects for Australia's Sarus Cranes.

Breeding for success

A story of the Sarus in Queensland

by Dr KS Gopi Sundar

Eleven of the world's 15 crane specieshave populations low enough to classify them as being of global conservation significance. The Sarus Crane is, sadly, one of these eleven species. The Sarus is spread across disjunct populations in south Asia, south-east Asia and north-east Australia. This is a vast area, and getting a good perspective on how these cranes are doing has not been easy.

John Grant is one of the very few individuals keeping a close eye on all things Sarus in Australia. One aspect he's been carefully watching is the all-important question of how successfully they breed.

John Grant in the field

Dr John Grant climbs high to view Sarus Cranes in the Gulf (Swati Kittur)
Companions are K.S. Gopi Sundar and Inka Veltheim

Breeding success is a fundamental element required to understand how populations of a species are doing: a higher rate of successful breeding signifies both good populations and good conditions. The problem is that this metric can change for various reasons. One important reason today is rainfall. Sarus thrive in wet conditions, but not too wet because this would cause flooding of their nests, and not too dry because this can prevent them from breeding altogether. Observations of breeding success over multiple years are therefore essential to understanding the limits of species like the Sarus.

Reaching the nesting grounds of the Sarus in far north Queensland is easier said than done. The sparse road network, the vast areas of privately managed lands, and treacherous field conditions created by the large number of streams and wetlands – and even crocodiles – come together to make this area inaccessible during the nesting season. Keeping track of individual nests and pairs, to figure out how each fared with their breeding, would have been ideal. But this has not yet been possible. So John had to devise alternate ways to measure breeding success in Sarus.

Cranes on ploughed field

Sarus Cranes feed on maize stubble and pasture on the Atherton Tablelands, with their recent young
(Sandy Carroll)

While the Sarus have annoyed field researchers in choosing difficult areas to nest in, they bring some cheer by flocking in the agricultural areas of the Atherton Tablelands after the breeding is completed. Here Sarus are spread out over a relatively small area that is very accessible, and is covered with farms with few trees making viewing easier than in the Gulf. After a few years of observations, John figured out he could easily distinguish young birds-of-the-year Sarus from birds that were older. He decided to keep careful track of these juveniles each year, and relate them to the total population. Using the excellent network of roads, a spotting scope and binoculars, and many many hours in the field, John measured breeding success in each of the winter months between 1997 and 2002. He covered the same area each month and year so his counts were comparable.

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This study revealed several things previously unknown. For one, the proportion of young birds was lowest early in the winter during May and June. During these months, he encountered very few flocks. The numbers then steadily increased until November. Clearly, the breeding Sarus were coming to the Tablelands steadily, and not all at once. This makes sense since not all pairs nest at the same time. Also, it takes a pair 30 days of incubation, and then 45-60 days before surviving young-of-the-year cranes can begin to fly. The pairs that nested earliest would likely arrive on the Tablelands first, followed by the ones that nested later.

This was very useful information! Counts in any one month in a year would likely not be completely indicative of the Sarus population. Though the Sarus were wintering in an area much easier to sight and count them, their behaviours added an element of complexity to field biologists interested in monitoring them.

John also discovered that young-of-the-year constituted, on average, 6.58% of the Tablelands Sarus population. This percentage varied year by year, as expected, but not by too much. The lowest percentage between 1992 and 2002 was 5.32% and the highest was 7.76%. This too was useful information. The Sarus nesting in the Gulf did not appear to experience too much fluctuation in their ability to raise chicks each year. For a bird that is globally-threatened, this is pretty good news.

Sandhill Crane flock

John was able to compare his results with breeding success for other species
(Sandhill Cranes, USA: KS Gopi Sundar)

Compare this with Sarus in India who breed almost entirely in landscapes covered with rice paddies. The variation in annual breeding success in Uttar Pradesh state in India was 4.6% to 13.8%, but with a much higher average of 9.22%. Globally, considering all crane species (for whom multiple years of breeding success data was available using methods similar to what John used), the average range in breeding was between 9 and 23%.

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The Sarus in Australia, for some reason, was not doing as well as other Sarus populations or other crane species are. Is this necessarily bad news? It is really difficult to say with any certainty. There is no data from past years or elsewhere in Australia to compare with John's observations. Maybe 6.5% is the norm for Australian Sarus? More than anything, this study revealed a few important features of the Sarus in Australia. One, it will require many years of careful and sustained observation to begin to understand how this species is faring. Two, despite this extensive data set spanning six years, we have too little information to confidently evaluate the status of Australia's Sarus Cranes.

We urgently need information from closely watching nesting pairs from multiple breeding locations of the Sarus in the Gulf. This may well require many more people like John doing much more, even perhaps multiple aerial surveys during the breeding time in each location.

With this study, John has raised the existing bar on Sarus ecology in Australia. The future of Sarus research and conservation in Australia promises to be rather exciting as researchers are armed with several key bits of information they can use to frame their own studies. For his part, John continues to wander the Atherton Tablelands in his weather-beaten jeep each year. Each new year gives another set of plots on a graph. And each year is a small step closer to uncovering the secrets of the Sarus.

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About the authorGopi studied Sarus Crane nesting in the heart of densely populated farming communities in India, then completed a PhD in conservation biology at the University of Minnesota focussing on agricultural landscapes that support people and wildlife. He is now Director of Program SarusScape for the ICF and NCF (India). Gopi has a deep interest in research and conservation for Australian Sarus Cranes, the least known Sarus in the world.

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