We studied Culex pipiens L. in the Niagara Region of Ontario, Canada, to establish whether or not these mosquitoes are attracted to hosts other than birds at different elevations or as the season progresses. Guinea-pigs and chickens were used as representative mammalian and avian hosts, respectively. Bait animals were placed next to modified CDC miniature light traps (no light and no CO₂) hung 1.5 or 5 m above ground in a Niagara woodlot. The season was divided into three 6-week periods (early, middle, and late). Significantly more C. pipiens were captured at the 5 m than at the 1.5 m elevation. In general, chicken-baited traps were preferred over control and guinea-pig-baited traps, with one important exception: there was no significant difference among traps during the late period at 1.5 m elevation. The potential role of C. pipiens as a bridging vector of West Nile virus to humans is discussed.