The numbers of House Finches or House Sparrows that ever tested positive (pos) or negative (neg) for WNV antibody transformed by ln(y+1) and regressed as a function of time retained within study areas grouped in 10 week intervals.

All slopes were significant (P2 is the coefficient of determination. Survivorship was estimated as was the backtransformed slope and measured retention within the study, with losses due to mortality and emigration. Mean age was expressed as weeks remaining within the study area.