Winter ecology of Pacific brant in Mexico and Alaska. Mid-winter counts of Pacific brant (Branta bernicla nigricans) have declined since 1961, and recently, have approached threshold levels for cessation of sport and subsistence hunting set by the U.S. Fish and Wildlife Service. This downward trend in population size coupled with increased rates of habitat degradation and loss at staging and wintering areas prompted joint research between the U.S., Canada, and Mexico to identify factors limiting population size and improve management of this sea goose. In 1990, the Alaska Science Center - Biological Science Office in cooperation with the University of Alaska-Fairbanks, U.S. Fish and Wildlife Service (FWS), Canadian Wildlife Service, Ducks Unlimited de Mexico (DUMAC) through the Institute of Waterfowl and Wetland Research (DU), and Secretary of the Environment, Natural Resources, and Fisheries of Mexico (SEMARNAP) initiated studies of brant at their primary breeding, migration stopover, and wintering sites in the Pacific flyway. Research has focused on an assessment of demographic parameters, such as fecundity and survival as well as examinations of migration patterns of the different breeding populations, relative population structure of brant at their primay wintering areas in Alaska and Mexico, and habitat use patterns relative to the availability and quality of the intertidal habitats. Demographic data from this research will be incorporated into a simulation model to explore the population dynamics of brant that can be used to examine different harvest strategies and devise management plans that will increase the population size of brant. More recent efforts have focused on accurately accessing the total extent of intertidal habitats in lagoons of Baja California, the primary wintering area for brant. Assessments will be used to develop baseline maps of seagrass distribution and abundance and provide the basis for monitoring long term change in this critical habitat. Moreover, findings from this research will be used local, state, and federal agencies to identify candidate areas for future conservation programs and provide guidance for future development activities. Another initiative includes an examination of habitat use patterns of a growing population wintering birds at Izembek National Wildlife Refuge in southwestern Alaska. Critical habitat used by this population could be compromised by development of new road and marine landing.