Bird migration strategies: linking individual decisions and population processes

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Migration is a phenomenon that allows individuals to anticipate or respond to variation in resources, disease or predation risk, and inhospitable conditions. Migratory strategies therefore vary, evolve rapidly, and affect population dynamics. Bird populations are often composed entirely of obligate migrants, but it is increasingly apparent that partially migratory populations, composed of both migrants and residents, are common. This poses further questions. Why do some individuals migrate while others do not? Does the migratory strategy of an individual change in response to environmental conditions? How does the movement of migrants influence other populations and communities? My research program aims to understand the ecological processes that underpin variation in migration, investigate how climate and land use change influence migratory strategies, and evaluate how anthropogenic stressors and migratory strategies interact to influence individuals, populations and communities. I propose research on black oystercatchers that will evaluate hypotheses for partial migration, determine the degree to which migration is a fixed or plastic trait that varies with climatic conditions, and examine the consequences of migration for individuals and populations. We will study oystercatchers both in Alaska, where the breeding population is composed of residents and migrants, and in BC, where the wintering population is composed of residents and migrants from further north. We will determine whether individuals migrate or not using a combination of tracking tags and stable isotopes, and ask if the decision to migrate varies with environmental conditions or the size, age and sex of an individual. We will use state of the art satellite tags to evaluate how the presence and density of migrants from Alaska influences the winter habitat use of residents in BC. Monitoring of survival and reproduction across years and sub-populations will allow us to evaluate whether selection for migration can maintain multiple migratory strategies or climate change will favour increased levels of residency. This research will advance our understanding of migration and inform models that can forecast how complex partially migratory populations will respond to environmental change. I also propose research that will examine how the arrival of seasonal migrants, that can double the density of songbirds on the wintering grounds in Mexico, influences avian communities in the tropics. This work, conducted in Jalisco, Mexico, will examine how the resident bird community associated with dry forests changes as this threatened habitat is converted to agriculture. We will also ask how the arrival of migratory Passserina buntings influences the behavior, condition and survival of an endemic resident, the orange-breasted bunting. This work will determine how landscape change and inter-specific competition between migratory and resident birds influence bird communities in the tropics.