|[Image: Arthur Grosset]|
This research clearly shows that even low pathogenic infections in migratory birds will eventually result in higher rates of mortality because these malnourished and weaker birds are more likely to fall victim to predatory birds or starvation. Which means that, while these birds do not look ill, they certainly are weakened by the Influenza A viruses.
 Latorre-Margalef et al: Effects of influenza A virus infection on migrating mallard ducks in Proceedings, Biological Sciences - 2009
 Van Gils et al: Hampered foraging and migratory performance in swans infected with low-pathogenic avian influenza A virus in PLoS One - 2007