Increasing avian pox prevalence varies by species, and with immune function, in Galápagos finches

► Avian pox prevalence increased rapidly in Galapagos finches from 2000-2009. ► Lack of a comparable increase in proportion of recovereds suggests high mortality. ► Increase in prevalence and level of susceptibility varies across species. ► Variation in innate immune function appears to underlie these species differences. ► Variation in immune function also appears to underlie annual variation in prevalence.