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As a research wildlife biologist at the U.S. Geological Survey (USGS), John Takekawa conducts most of his work on coastal and estuarine birds of North America's west coast, but this past summer found him in Asia on the grassland steppe of northeastern Mongolia. There, he and colleagues attached global-positioning-system (GPS) satellite transmitters to wild whooper swans in a study that will shed light on the whooper swans' migratory patterns and help reveal how wild birds may be involved in the spread of avian influenza.
Many of the populations Takekawa studies migrate from the coast to breeding grounds in remote inland areas (see "Finding the Needle in a Big HaystackLocating Surf Scoter Nests in the Northern Boreal Forest" in Sound Waves, August 2005). Whooper swans breed on shallow lakes and slow-flowing rivers in northern Eurasia and winter on agricultural land near coasts. Their breeding areas are distributed from Iceland to northeastern Siberia, and their wintering areas from Europe to coastal China and Japan. The whooper swans depart from breeding areas in September and reach wintering areas by November, leaving in mid-March for a May return. As much as 60 percent of the global population of more than 100,000 are found in the western Palearctic (Europe, Asia, and northern Africa) during the winter. They feed on aquatic plants and grasses in the breeding season, with added food from crop fields in the winter.
In August 2006, a team of international scientists from the USGS and the United Nations Food and Agriculture Organization (FAO) joined the Wildlife Conservation Society (WCS) and the Mongolian Academy of Sciences (MAS) in a whooper-swan surveillance project that is part of the Wild Bird Global Avian Influenza Network for Surveillance (GAINS) program funded by the U.S. Agency for International Development (USAID). The team attached lightweight, solar-powered GPS transmitters to wild whooper swans in an effort to track the birds to their wintering grounds.
Such research is providing information on migration routes and informs governments about potential threats from such diseases as highly pathogenic avian influenza (HPAI). The HPAI strain known as H5N1 is extremely lethal for various bird species, especially poultry and some waterfowl species. When transmitted to people through close contact with infected birds, the virus can be deadly. Leaders across the world are concerned about a potential pandemic threat should the virus become transmissible among humans.
"We are working to understand the role wild birds may play in the spread of H5N1," said Scott Newman, a WCS field veterinarian working as International Wildlife Coordinator for Avian Influenza for the FAO, based in Rome, Italy. "Although poultry and bird trade are probably the primary routes of movement, migratory birds are likely involved in some areas." Recommendations from the FAO-OIE International Scientific Conference on Avian Influenza and Wild Birds in Rome include improving our understanding of wild-bird behavior, precise migratory strategies, sites of aggregation and convergence, and interactions between wildlife and domestic species.
The whooper swans drew increased attention after large numbers perished in Mongolia in 2005 and in western China in 2005 and 2006 in areas where few poultry are present. Subsequent sampling of the dead swans by WCS scientists verified that some of the swans were infected with HPAI. This discovery suggested that HPAI may be moving through the region and may spread from it, prompting the study to identify where these migratory-bird populations fly in the winter.
"Although we are sampling wild birds for avian influenza in the field, we will not be able to fully understand their role in this disease unless we better understand their movements," said William Karesh, WCS's director of the Field Veterinary Program in New York and coordinator of the GAINS system. "WCS samples birds in East Asia under the GAINS program, but when we find infected birds, we need to know where they are going."
Many migratory-bird species nest thousands of miles from where they spend the winter, and it is difficult to determine which groups come from which areas, said Takekawa, whose work as a member of the USGS Western Ecological Research Center in California has included extensive use of radio telemetry to track migratory birds. "We are marking swans with very small GPS transmitters that are similar to navigation systems on cars, but that transmit their locations back to us through weather satellites so we can track their movements."
Whooper swans were captured by the international team in early August on the grassland steppe of far eastern Mongolia, near the borders with Russia and China. Each year, swans molt their feathers after the breeding season; during that flightless period, the birds were captured by biologists in boats and on foot. Small, 70-g (2.3 oz, or the weight of a dozen quarters) solar-powered transmitters were affixed on 10 of the 8-kg (18 lb) large swans with backpack harnesses. The harnesses are made of Teflon ribbon that deteriorates and falls off the birds within a few years.
Takekawa noted that satellite-tracking data will provide information that will not only help scientists better understand and document links between wild birds and the spread of avian influenza but also help enhance conservation efforts through determining the nonbreeding ranges of birds and the mechanisms involved in long-distance migration.
The GPS transmitters are made by a wildlife specialty company (Microwave Telemetry, Inc., of Columbia, Md.); only in the past 5 years have they been reduced to a size suitable for migratory birds. The transmitters' locations, with an accuracy better than 30 ft, provide a wealth of information on migrating birds and use of their habitats that was unavailable before. The locations are recorded every 2 hours and stored in the transmitter's memory before being sent to the research team by e-mail every 2 days through weather satellites.
Whooper-swan locations are being updated twice weekly on a project Web page, which also includes access to the data in Google Earth format. A comprehensive database of information on international wild-bird avian-influenza surveillance and migratory-bird activity is posted on the WCS Web site. Biologists David Douglas (USGS Alaska Science Center) and Diann Prosser (USGS Patuxent Wildlife Research Center) are coinvestigators in the study and are providing assistance with analyses and fieldwork.
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