Possessing annual estimates of black duck population characteristics, including abundance, sex and age structure, and vital rates (i.e., survival and recruitment) is critical to fulfilling the mission of the BDJV and achieving the goals of the NAWMP. These estimates form the basis of black duck adaptive management and allow researchers and managers to assess model predictions, evaluate responses of black ducks to management, and track progress towards NAWMP goals. Black duck population monitoring consists of three complementary programs: pre-season banding, the Mid-Winter Inventory, and Eastern Breeding Waterfowl Survey.
The Mid-Winter Inventory (MWI; also known as the Mid-Winter Survey) has been conducted in the United States since 1955. Because it provides the longest time series of black duck abundance data the MWI have been used extensively in research, particularly population modeling. However, the MWI has several limitations. First, it is only conducted in the United States so it does not provide an estimate of the entire wintering population. Second, recent research suggests the distribution of wintering black ducks may have shifted north, further limiting the usefulness of the MWI. Third, the MWI lacks the precision necessary to monitor population changes and does not provide estimates of variance. Finally, the MWI cannot be used to differentiate regional changes in breeding populations. A MWI has been conducted in Ontario by Environment Canada-Canadian Wildlife Service since 2002 and provides an index of abundance along the north shore of lake Ontario.