Oviposition is a critical stage in the mosquito lifecycle, and may determine population levels, distribution, biting behavior, and pathogen transmission. Knowledge of the oviposition behavior of Culex restuans Theobald has become particularly important with the emergence of West Nile virus (WNV) in North America. Laboratory and field studies have examined some factors that contribute to oviposition choice in Culex spp., but few studies have investigated responses to cues of future competition and breeding habitat availability in the field. We hypothesized that female Cx. restuans mosquitoes avoid laying eggs in habitats containing cues of larval competition, and that increased availability of larval habitat decreases egg density. To test these hypotheses, a series of field experiments were conducted in southeastern Michigan during summer 2002. We found that female mosquitoes prefer nutrient-enriched containers and decrease ovipositing in containers with conspecific larvae. In addition, greater habitat abundance decreased egg clutch density per container, although there was considerable aggregation of egg clutches. These results support our hypotheses and have potentially important implications for pathogen transmission by mosquitoes.