Abstracts

Presented by Ray T. Alisauskas - Email: ray.alisauskas@canada.ca

Hunting has the potential to affect survival and population size of waterfowl. This notion motivates much effort in North America toward direct estimation of abundance, harvest and survival for a wide array of waterfowl species. Before aerial survey for counting waterfowl became institutionalized, Lincoln proposed an alternative method in the 1930s for range-wide population estimation; his idea was based on the integration of (i) data from band recoveries and (ii) estimation of total harvest, without ever counting free-ranging birds. Lincolns estimator relies on information voluntarily supplied by hunters to inform it, providing an early example of the role of citizen science for understanding wildlife population dynamics. I review Lincolns method, the assumptions that must be satisfied for its use as a suitable estimator of abundance, and the additional inferences about population structure that it allows, which are not readily available from aerial survey data. I examine differences in the two estimation approaches (Lincoln vs. aerial counts). Lincolns method depends on reliable, in-hand identification of the species, age, and sex of both banded and harvested waterfowl. Abundance estimates pertain to the time that birds are marked so that much of the waterfowl banding in North America that occurs in late summer provides preseason population estimates of 4 sex-age cohorts; in a similar fashion, winter banded samples could be used to estimate winter abundances. A number of different waterfowl populations are used as examples to illustrate how past dynamics of abundance, recruitment and sex ratios can be reconstructed using Lincolns method. Additional tests of density dependence and the role of habitat conditions on annual recruitment at the population level are possible.