"Songbirds such as sparrows and thrushes carry various forms of bird flu and could potentially spread the viruses to pigs and poultry, U.S. researchers reported on Tuesday.

The birds carried low-pathogenic avian influenza -- the less dangerous form of bird flu -- but flu viruses can and do swap genes and mutate into more dangerous forms, the researchers said.

A major risk is that the birds would infect pigs, which are suspected "mixing vessels" for new strains of influenza -- notably the ongoing pandemic of H1N1 swine flu, the researchers wrote in the Biomed Central journal BMC Infectious Diseases, available here"

Maggie Fox reports for Reuters July 7, 2010. [2]