From 2001 to 2008, we estimated probabilities of survival and encounter of adult House Finches (Carpodacus mexicanus) breeding at Stone Lakes National Wildlife Refuge, Sacramento County, California, from capture-recapture data on birds trapped with mist nets and ground traps. Our primary objectives were to determine when West Nile virus (WNV, Flaviviridae, Flavivirus) arrived at the site and if survivorship changed after this arrival. We monitored viral activity by screening blood samples from House Finches for WNV antibodies with an enzyme immunoassay and by testing mosquito pools for viral RNA. WNV arrived after the breeding season in late 2004, so we compared data from 2001–2004 (pre-WNV) to that from 2005–2008 (post-WNV). We found a decrease in annual survival following the arrival of WNV (pre-WNV, 0.59; post WNV, 0.47), which, if representative, may have contributed to the reported decline in the abundance of this species in northern California.