Factors Regulating Population Size and Colony Distribution of Adelie Penguins in the Ross Sea

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9814882David Ainley This renewal project investigates the demographic and life-history mechanisms responsible for geographic structuring of colonies, the founding of new colonies and recent dramatic change in the size of existing colonies of Adelie penguins Pygoscelis adeliae. The project will examine (1) the relative importance of resources that constrain colony growth - availability of nesting habitat versus access to food; (2) those natural history and demographic parameters that might be affected by exploitative or interference competition, in turn mediated by colony size (e.g. breeding and foraging effort and success); and (3) behavioral mechanisms that influence colony growth as a function of initial size and distribution (e.g. philopatry - the immigration-emigration balance). In this first empirical a priori study to consider the geographic structuring of a seabird population, we ask, Why do neighboring penguin colonies differ in size? Why are new colonies founded? Overall, the methods will bring together several well-established techniques, e.g. aerial photography for assessment of nesting habitat, satellite images for examination of sea ice extent, radio telemetry for assessment of overlap in colony feeding areas, tagging to assess demographic parameters and dispersal, and time depth recorders and doubly labelled water for determination of energetic costs of foraging. Results will increase understanding of population regulation and patterns of dispersion, and the effects of climate change, mediated through changes in sea-ice cover, on penguin populations. In addition, results will provide a context in which to interpret conflicting data on penguin population trends from existing programs that use Adelie penguins as an indicator species for point source anthropogenic impacts on Antarctic fishing resources.