Breeding Season Survival of Female Lesser Scaup in the Northern Boreal Forest

One hypothesis advanced to explain the decline in lesser scaup (Aythya affinis) populations during the past 20 years is that adult female survival has decreased. However, no survival probability estimates exist for the boreal forest, the region where most scaup breed. We captured and radio-marked female lesser scaup (n = 42) near Yellowknife, Northwest Territories, Canada, just before the breeding season in 1999 and 2000. Constant weekly survival probability was estimated using a Cormack-Jolly- Seber model (0.96). We extrapolate this rate to estimate survival probability for the nesting season (0.80, SE = 0.09), the period when females are at greatest risk of predation. Recent estimates of annual mortality (42%) suggest that about 50% of annual female mortality occurs during the breeding season, a result similar to recent conclusions from studies of prairie-nesting lesser scaup. Further, our survival estimate provides information required to produce preliminary models of population dynamics for boreal lesser scaup, a step that could greatly improve our understanding of decline in this species.