The foraging habits and resultant functional response of American black ducks

Abstract

The American black duck (Anas rubripes) is an outcome species for the health of the Chesapeake Bay. In order to estimate the impact that changes in black duck habitat will have on the Bay’s wintering population, the relationship between black ducks and the species comprising their diets must be better understood. This study was part of a larger effort to build a comprehensive bioenergetics model for black ducks wintering in the Chesapeake Bay. Using black ducks as model species, functional response curves were created for five experimental species known to be consumed by black ducks. For each curve, three regressions representing the three types of functional response models were run. In examining the regression fits along with using biological inferences, the functional response types for each experimental species were determined to be type I for softstem bulrush seeds, type II for widgeon grass, horned pondweed, and Eastern mosquitofish, and type III for saltmarsh snails. This research was used to determine critical foraging densities and will contribute to the bioenergetics model that will help identify areas where conservation efforts should be targeted in order to benefit black ducks and contribute to the overall health of the Chesapeake Bay.