Attraction of Culex quinquefasciatus Say, Culex tarsalis Coquillett, Culex nigripalpus Theobald, and Aedes aegypti (L.) to avian and other host odors was investigated in a dual-port olfactometer. Although attraction to a human arm was high for Ae. aegypti (>80%) and low for all Culex spp. (<25%), all species responded similarly to a chicken (55.3–73.6%). Responses of Ae. aegypti, Cx. quinquefasciatus, and Cx. nigripalpus to feathers were low (<20%) but greater than to controls. There was no difference in attraction of Cx. tarsalis to feathers or controls. Responses to CO₂ (5 ml/min) were low for all species (<15%) except Cx. tarsalis, which were moderate (24.5%). When feathers were combined with CO₂, the resulting attraction was additive or lower than responses to feather and CO₂ alone for all species except for Cx. tarsalis, which had responses that were three-fold greater than expected if responses were additive. The CO₂–feather treatments were less attractive than a chicken for all species. When olfactometer assays were extended from 3 to 20 min, responses by Ae. aegypti significantly increased to a chicken and CO₂ and attraction of Cx. quinquefasciatus significantly greater to chickens, CO₂, and feathers. None of the volatile compounds previously identified from feathers or uropygial glands tested were attractive. Both feather-rubbed cotton balls and hexane extracts of feathers were attractive and as attractive as feathers; however, ether extracts were not attractive. Feathers clearly contribute to the attraction of host-seeking Culex spp., and future studies will focus on identification of the attractant compounds.