S42.Summary: Advances in crane research

In contrast to the Whooping Cranes that have made a gradual recovery during the last half of this century, ten species of cranes in Asia and Africa declined during this period. Among these species, the Siberian Cranes Grus leucogeranus remain in greatest peril. Surprisingly, for such a rare bird, little was known about its biology until recently. Dr. Alexander Sorokin of the Russian Institute for Nature Conservation, discovered in 1981 the nesting area of the Siberian Cranes that migrate to India, and in 1996, together with Dr. Yuri Markin, discovered the nesting grounds of the population that winters in Iran. Dr. Sorokin and Claire Mirande provide an account of biology of the Siberian Cranes in western Asia and of ongoing efforts to conserve and bolster populations now perhaps reduced to fewer than fifteen individuals in the wild. Fortunately, an East Asian population numbering approximately 3000 and a flourishing captive population of 120 cranes provide greater security for the species. But now the wintering grounds of the eastern population are perhaps threatened by the effects of the construction of the Three Gorges Dam across the Yangtze River in China. Many of the techniques pioneered in the USA to help the Whooping Cranes are being applied to aid the Siberian Cranes. In addition, conservation efforts organised through Secretariat of the Convention on Migratory Species in Bonn, Germany, help co-ordinate activities of the ten nations to which this transcontinental migrant is native.

Conserving the links in a chain of wetlands is vital in conserving migratory cranes. Discovering these links has been the task of Dr. Hito Higuchi from Tokyo University and his colleague, Mr. Yutake Kanai, at the Wild Bird Society of Japan. By attaching radio transmitters to cranes on their wintering grounds in Japan and on their breeding grounds in China, and using a satellite to monitor the locations of the transmitters, migration routes were mapped and important resting areas - the links in the chain - were determined. For the first time, key areas in North Korea were identified in a closed nation where ground surveys had not been possible. Subsequently, the Japanese researchers were allowed to visit these areas. Conservation recommendations were then advanced to the authorities in North Korea. The satellite telemetry studies also demonstrated the importance of the Demilitarized Zone between North and South Korea as the critical wintering areas for Red-crowned Cranes Grus japonensis that breed along the basin of the Ussuri river along the China-Russia border, and as the most important migration resting area for White-naped Cranes Grus vipio that winter in Japan.

Another benefit from satellites is the use of remotely sensed imagery, which can be analysed with a Geographic Information System (GIS) to depict habitat conditions from small scales (i.e., 10 hectares) to large scales (i.e., 1000 ha +). Ms. Amy Richert from the University of Nebraska-Lincoln demonstrated how the integration of remote sensing and GIS techniques were used to understand more about the selection of stopover habitat by Whooping Cranes in Nebraska. Results of the study showed that colour infrared photographs and thematic Mapper imagery were accurate enough for studying roosting habitats at multiple spatial scales, but that satellite imagery was most efficient for large areas. The methodology used is applicable for studying multiple-scale habitat conditions for crane species worldwide, because the authors considered spatial analyses for a diversity of landscape patterns and statistical analyses of populations that tend to be small and clustered throughout large, remote areas.

Finally, the Crane Session included a report about the least known of cranes, the Black-necked Cranes of western China. First discovered in 1876 near Lake Koko Nor (Tibet) by the Russian explorer and naturalist, Dr. Nikolai M. Przhevalski, little was known about their biology and status until work by Dr. Li Fengshan and Dr. Mary Bishop. Although most of the known breeding areas are high altitude wetlands with little impact for nomadic pastoralists. The cranes are threatened on their wintering grounds in southeastern Tibet and in Yunnan and Guizhou where wetland reclamation, changes in traditional agricultural practices, and persecution of the cranes in some areas, are threats. Cranes no longer frequent some former wintering sites in Yunnan. The world population of Black-necked Cranes is estimated to be a minimum of 5500 - 6000.

Cranes worldwide are most threatened in regions of high populations of humans. Ironically, although cranes require wider expanses of wetland habitat per breeding pair on their breeding grounds than on the wintering grounds where cranes often gather in flocks, winter habitat is often more limiting than breeding habitat. The rare migrants on the northern continents nest in remote wilderness areas at high latitudes where there are less pressures from humans. In like manner, cranes that are non-migratory in warmer climates ultimately face greater pressures from expanding human populations. Consequently, with the exception of the Brolgas Grus rubicunda of Australia, the cranes resident in southern Asia, in sub-Saharan Africa, and in southeastern USA and in Cuba, are threatened. Efforts should be made to conserve populations before they follow the path of the Whooping Cranes and the Siberian Cranes, species for whom expensive conservation programs continue.