American black duck summer range versus winter range: a dichotomy of riches

Abstract

The status of the American black duck (Anas rubripes) population has more often been attributed to a single event than to multiple events over time and throughout space. The difference in the quality of the habitat, however defined, within breeding areas in the North and in the southerly wintering areas, especially Chesapeake Bay, also has been proposed as affecting black duck status. The obvious question is 'What variable cuts across all habitats, time, and space to affect black ducks?' This paper attempts to answer that question by examining the connectivity of seemingly unrelated variables and events associated with the black duck's summer range and its winter range relative to population change. Insights from examples of relations among these variables reveal how results may be confounded and even misleading. A perspective that may be required to ensure future black duck populations is discussed.