Migratory birds breed throughout the temperate regions of North America but winter in very different habitats further south. Although 1000 km or more may separate wintering from breeding areas, recent research has revealed that ecological conditions during winter can influence subsequent reproductive success. The major objective of this research is to investigate the underlying physiological factors linking winter events with an individual's ability to breed. The American redstart (Setophaga ruticilla) is an excellent study animal: its ecology and behavior during the wintering and breeding periods have been intensively studied. The degree to which redstarts prepare for breeding, and the factors that influence this, while still on their winter territories will be investigated by analyzing the links between natural and experimentally induced variation in winter habitat quality (food availability), the birds' energetic condition (body mass, fat stores, plasma indicators of energy storage and use), and their breeding status (reproductive hormones) before they leave the wintering grounds. Similar measures of energetic and reproductive condition will also be taken in redstarts as they arrive at the breeding grounds. Stable-carbon isotopes, as markers of winter habitat origin, will be used to link winter and summer events. This research provides greater understanding of how different periods of an individual's life cycle interact to influence reproductive success, will contribute significantly to our understanding of how migrant bird populations are regulated, and will ultimately help resource managers direct conservation efforts more efficiently. The broader impacts of this research include the opportunity to greatly enhance the breadth of professional training of many students, particularly those from underrepresented groups, through its integration of physiology, behavior, and ecology and a variety of lab and field methods, and will strengthen ties with conservation groups in Jamaica.
