This is the final version of the article. It first appeared from the Society for General Microbiology via http://dx.doi.org/10.1099/vir.0.000155 ; Low pathogenic avian influenza A viruses have a natural host reservoir in wild waterbirds and the potential to spread to other host species. Here we investigate the evolutionary, spatial and temporal dynamics of avian influenza A viruses in Eurasian wild birds. We use whole genome sequences collected as part of an intensive long-term Eurasian wild bird surveillance study and combine this genetic data with temporal and spatial information to explore the virus evolutionary dynamics. Frequent reassortment and co-circulating lineages were observed for all eight genomic RNA segments over time. There was no apparent species-specific effect on the diversity of the avian influenza A viruses. There was a spatial and temporal relationship between the Eurasian sequences and significant viral migration of avian influenza A viruses from West towards Central Asia. The observed viral migration patterns differed between segments. Further we discuss the challenges faced when analysing these surveillance and sequence data and the caveats to be borne in mind when drawing conclusions from the apparent results of such analyses. ; We thank all ornithologists and other collaborators for their continuous support. We thank V. Munster, E. Skepner, O. Vuong, C. Baas, J. Guldemeester, M. Schutten, G. van der Water, D. Smith and E. Bortz for technical support and stimulating discussions. This manuscript was prepared while D.E. Wentworth was employed at the JCVI. The opinions expressed in this article are the author?s own and do not reflect the view of the Centers for Disease Control, the Department of Health and Human Services, or the United States government. This work was supported by NIAID/NIH contract HHSN266200700010C, HHSN272201400008C, HHSN272201400006C and HHSN272200900007C, a Wellcome Trust Fellowship Strategic Travel Award under contract WT089235MF, a DTRA FRCWMD Broad Agency Announcement under contract HDTRA1-09-14-FRCWMD GRANT11177182, by the EU Framework six program NewFluBird (044490) by contracts with the Dutch Ministry of Economic Affairs and a NIAID/NIH CEIRS travel grant under contract HHSN266200700010C. The Swedish sampling and analysis was supported by the Swedish Research Councils VR and FORMAS.