Every day at dawn, bird lovers can still be seen taking their caged pets for walks in parks and lakeside areas across the Yangtze River Delta, despite the area being ground zero for the most recent avian flu outbreak. Some researchers suspect that the H7N9 virus may have evolved from diseases found in both local birds and in Korean fowl that migrate to the region. However, not all bird aficionados have been deterred as a rising number of cities across the region close poultry markets and mull a ban on live poultry sales. The delta, which comprises parts of Jiangsu and Zhejiang provinces, as well as Shanghai, has a rich history of bird breeding that dates back several centuries. Since the Song dynasty (960-1279), keeping and displaying songbirds and other pet birds in the region has been common. In Nanjing, Jiangsu's capital, more than 300,000 people have white-eyes - songbirds with white feathers around their eyes - according to the provincial birding association. Mynah birds and song thrushes are highly sought-after as pets by those who enjoy their beautiful feathers and chirping. Owners often hang their ornate bamboo bird cages on low tree branches to be appreciated by passers-by as they chat with friends, exercise or play. Before the outbreak of H7N9, it was easy to find dozens of species of birds at pet markets in cities across the delta. Most of them are migratory birds caught by local villagers. A vendor at a bird pet market in Hangzhou said: "Bird lovers generally take the male birds as pets. They can sing and look colourful." She said a normal song thrush costs about 100 yuan (HK$124) at her shop, but more vocal and lively male birds may sell for hundreds or even thousands of yuan. A Nanjing man in his 50s, who declined to be named, said: "I can stop eating poultry, but I can't stop keeping birds as pets." And a 70-year-old retired resident of Hangzhou said: "Strolling on the lakeside with a bird in its cage is one of the most wonderful things in the world. I don't fear the bird flu, but I fear not having a pet bird." It is possible for migratory birds to spread unknown viruses to poultry and people. This is the season when a large number of migratory birds arrive in the Yangtze River Delta. It could be dangerous With hundreds of thousands of people in the region keeping birds as pets, it has created high demand for the illegal trapping of migratory birds, particularly in the wetlands of the Yangtze River Delta that are important habitats for East Asian migratory fowl. But experts say that poaching can create health risks, as birds that migrate between continents may carry pathogens that could infect other native birds, particularly when they're grouped together in captivity. "There are nearly 500 species of birds in Zhejiang and more than half are migratory birds," said Chen Shuihua , deputy head of the Museum of Natural History in Zhejiang. "It is possible for migratory birds to spread unknown viruses to poultry and people. This is the season when a large number of migratory birds arrive in the Yangtze River Delta. It could be dangerous."