The demography of the New Zealand shoveler
- Wilidlife Service, Department of Internal Affairs, Private Bag, Wellington, New Zealand
[Abstract of a paper read at the Ecological Society Conference, 1983.]
Between 1972 and 1979, 1003 adult and 976 juvenile shoveler (Anas rhynchotis variegata) were banded. By July 1982, 184 adults and 171 juveniles had been reported short. The mean annual survival rate of adults was 58% (95% conf. into 53-64%) and those surviving their first year after banding had a mean expectation of further life of 1.8 (1.5-2.3) years. The mean annual survival rate of juveniles in their year of banding was 50% (37-64%). To maintain a stable population, each breeding pair is required to raise 3.4 young to fledging; limited field studies suggest an average annual production of 3.6 young. Some slender evidence indicates a tendency toward ancestral breeding but otherwise shovelers demonstrated a pattern of high mobility throughout the country.