Nesting and brood ecology of Lesser Scaup at Waterhen Marsh, Saskatchewan

Abstract

E. 1977. Nesting and brood ecology of Lesser Scaup at Waterhen Marsh, Saskatchewan. Canadian Field-Naturalist 91(3): 248-255. Abstract. The nesting and brood ecology of the Lesser Scaup (Aythya affinis) was observed at Waterhen Marsh in central Saskatchewan. Most scaup nests were initiated during the first two weeks of June and the peak of hatching occurred during the middle two weeks of July. The mean clutch size was 9.70 + SE 0.21 (n = 56); if clutches of 13 and 14 are omitted, the mean becomes 9.47 + 0.18 (m = 53). Several incidents of egg parasitism involving scaup were noted. Insular, well-concealed nest sites featuring plants (especially grasses) in the 21-to 60-cm height range were often selected. Twenty-eight (76%) of 37 nests were successful. Striped skunks (Mephitis mephitis) and Common Crows (Corvus brachyrhynchos) caused most of the nesting failures. The high social tolerances exhibited by brooding scaup and the concentration of broods in areas of suitable habitat resulted in the formation of mixed broods. Redhead (Aythya americana) ducklings frequently joined these broods. Possible advantages of this créching are discussed.