Some aspects of avian utilization of sewage oxidation lagoons

The utilization of two sewage oxidation lagoons at Port Williams, Nova Scotia, by three species of shorebirds (Greater Yellowlegs, Least Sandpipers, and Spotted Sandpipers) and Black Ducks was appraised by observing times of occurrence and behavior over a seven week period during August and September, 1976. A seasonal decline in numbers, observed for shorebirds, was not evident for Black Ducks. Daily variation of numbers was investigated for correlation with tidal fluctuation for the adjacent Minas Basin and to changing light intensity. Shorebirds exhibited a reponse in numbers with respect to time of high tide but not to changing light intensity. Black Ducks demonstrated no trends in numbers present in relation to tide time. Rather, changing light intensity appeared to affect the numbers present. Light intensity appears to be the basis for the diurnal cycle of occurrence of Black Ducks at the sewage lagoons. The majority of hours shorebirds were present at the lagoons was devoted to feeding. Black Ducks spent most of the daytime loafing at the lagoons and fed when most were present at times of dawn and dusk. Shorebirds, when displaced from natural feeding habitat by high tides, utilized the lagoons to extend their amount of foraging time to accumulate the fat reserves necessary for migration. Black Ducks utilized the lagoons as a rearing area for ducklings prior to the start of this study, and as a loafing and feeding area throughout the period of study.