Demography and landscape interactions of goose populations on the Yukon-Kuskokwim Delta, Alaska. The Yukon-Kuskokwim Delta (YKD) is the most important breeding area for geese in western North America. The YKD is the sole nesting area for cackling Canada geese, the preponderance of the world's emperor geese, and most of the Pacific Flyway's greater white- fronted geese and black brant. The vulnerability and volatility of these goose populations has been well documented. Since the mid 1980s, the Alaska Science Center (ASC-BSO) has been studying aspects of the breeding biology and migration ecology of all four goose species breeding on the YKD. These studies have identified factors directly contributing to mortality and survival. However, the complexity of demography in these long-lived species is such that we still lack much understanding and are unable to make accurate predictions of future population dynamics. An ultimate goal of our research is to develop a realistic, empirically based model that will describe and predict population trends in this suite of goose species. Specifically, we plan to build on prior studies by investigating the influences of age structure, spatial variation, and interspecific competition on trophic level interactions and population dynamics. We need knowledge about the age structure of populations and how demographic characteristics vary with age. Theoretical studies have demonstrated the profound effect of age structure on demography, yet for avian species, little data on age structure exists and is only obtainable through long-term marking programs. Second, we will broaden our demographic focus to include estimation and consequences of spatial movements and philopatric behavior. The great spatial variability in plant communities suggests that demography of geese may have a strong spatial component as well. Further, source-sink dynamics and vulnerability to harvest are also expected to be functionally related to patterns of philopatry. Third, we plan to continue documenting how demographic components vary annually, but also initiate an experimental phase to more clearly discern what factors may be causing the annual variations in reproduction and survival that we have and will observe. A goal is to discern trophic level interactions in these demographic traits, e.g., are survival rates disproportionately influenced by predation (human and non-human) on these herbivores or by changes in the vegetative communities upon which the herbivores forage. Concurrent with ecological studies to elucidate demographic patterns, we need to also better understand subsistence harvest dynamics. Indigenous people are an integral component of this ecosystem and at present we do not even know what is the age composition of their harvest. Our approach for investigating population biology of geese on the YKD is necessarily with a community rather than single species focus. Population trends of the four goose species vary and densities are highly dynamic. We know there is some degree of niche overlap among goose species, but we as yet do not know the degree of interspecific competition or its demographic significance. Investigation of competition among goose species will also have direct bearing on our understanding of goose use of plant communities and goose distribution across landscapes. Thus, these studies of population biology and competition within and among goose species will directly link with concurrent studies of the effects of global change on plant and landscape processes. Climate change is predicted to have significant effects on the distribution and composition of forage plants, and consequently, we expect such effects to cascade up to the dominant herbivores in this system, the geese. Our linked studies will provide an ecosystem approach for evaluating these relationships and whether demographic variations in goose populations may serve as sentinels of ecosystem change.