Influence of Age and Selected Environmental Factors on Reproductive Performance of Canvasbacks

Age, productivity, and other factors affecting breeding performance of
canvasbacks (Aythya valisineria) are poorly understood. Consequently, we tested
whether reproductive performance of female canvasbacks varied with age and
selected environmental factors in southwestern Manitoba from 1974 to 1980.
Neither clutch size, nest parasitism, nest success, nor the number of
ducklings/brood varied with age. Return rates, nest initiation dates,
renesting, and hen success were age-related. Return rates averaged 21% for
second-year (SY) and 69% for after-second-year (ASY) females (58% for
third-year and 79% for after-third-year females). Additionally, water
conditions and spring temperatures influenced chronology of arrival, timing of
nesting, and reproductive success. Nest initiation by birds of all ages was
affected by minimum April temperatures. Clutch size was higher in nests
initiated earlier. Interspecific nest parasitism did not affect clutch size,
nest success, hen success, or hatching success. Nest success was lower in dry
years (17%) than in moderately wet (54%) or wet (60%) years. Nests per female
were highest during wet years. No nests of SY females were found in dry years.
In years of moderate to good wetland conditions, females of all ages nested.
Predation was the primary factor influencing nest success. Hen success averaged
58% over all years. The number of ducklings surviving 20 days averaged
4.7/brood. Because SY females have lower return rates and hen success than ASY
females, especially during drier years, management to increase canvasback
populations might best be directed to increasing first year recruitment (no. of
females returning to breed) and to increasing overall breeding success by
reducing predation and enhancing local habitat conditions during nesting.