Air pollution has been found to have direct and indirect effects on forest passerines, but there is very little information on the effects of emissions from the pulp and paper industry. This long-term (7 y) study compares breeding parameters of Great tits in industrial and rural sites in maritime pine forests on the west coast of Portugal. We found that Great tits bred earlier, laid more eggs, and produced more fledglings in the industrial area, where we also found a higher biomass of caterpillars, an important food source for tits. There were also differences in ground arthropod numbers, the industrial area having more beetles and millipedes and the rural area more spiders and silverfish. Our results suggest that there are no direct toxic effects of emissions from the paper industry on the study species. However, invertebrate food availability is clearly related to pollution levels, which indirectly affect the breeding performance of the Great tit.