The fecal coliform loadings to the Rideau River from bird populations resident on bridges were measured for dry weather, summer, low river flows (8.5–17 m3 s−1). The Rideau River has typical velocities to 0.216 km h−1. The loadings were estimated by an intensive river sampling program over 4 weeks at river cross sections upstream and downstream of a bridge with birds on the bridge and without birds on the bridge. The birds were temporarily displaced from the bridge with bird nets. Statistical testing of the river cross section geometric means showed the birds do have a significant effect on river fecal coliform levels. From bird census, river water sampling data, and river flow data, a pigeon was estimated to generate on the average a daily loading of between 0.88 and 1.3 × 1010 fecal coliform organisms with a standard deviation of approximately 0.39 × 1010. An independent check on the validity of the estimated loadings from resident bird populations at another bridge produced results within 40% of the measured values. Keywords: fecal coliform loadings birds.