Hong Kong and international scientists are mapping the movement of migratory birds to and from Mai Po to try to determine whether wild birds play a major role in the spread of the deadly H5N1 flu. Wild birds have been a favourite target for blame in the spread of the H5N1 virus, which has ravaged poultry stocks across Asia since it re-emerged in 2003. The first human bird flu cases occurred in Hong Kong in 1997, and 258 people have died worldwide, including three on the mainland this month. The scientists from the United Nations Food and Agriculture Organisation, WWF Hong Kong, the University of Hong Kong's department of microbiology, Asia Ecological Consultants, and the US Geological Survey's Western Ecological Research Centre are collaborating in the effort launched on December 10. HKU professor of microbiology and team member Malik Peiris said: 'There is always controversy about wild birds spreading H5 and spreading it long distance, and there is limited information on exactly what are the routes of migration of the different types of birds in the Asian region.' About 24 migratory wild ducks - the northern pintail and Eurasian wigeon - wintering in the Inner Deep Bay wetland and Lok Ma Chau have been trapped and fitted with tiny satellite radio transmitters. The devices are able to record and transmit GPS locations and weekly information which will be captured on a Google Earth map site available for public viewing. Connie Leung Yin-hung, a veterinarian at the HKU department of microbiology, said scientists trapped 70 wild ducks in the wetlands, but only 24 were tagged because of a lack of transmitters. All 70 tested negative for bird flu viruses. Professor Peiris said the team would have some 'interesting information' within a year. 'If we know if the birds coming to Hong Kong are coming from elsewhere in Asia, and if we later find viruses that are commonly found somewhere in Asia, then we can link how the viruses are moving.' He said HKU had tested 30,000 samples from healthy wild birds in the Deep Bay area since 2003, and none had tested positive for H5N1.