Dissertation Research: Quantifying Edge, Behavioral, and Climatic Effects on Survivorship Estimates of an Area-Sensitive Non-Migratory Sparrow

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9902226Bolger & MorrisonResidential development has resulted in extensive fragmentation of the coastal sage scrub habitat in southern California. A long-standing problem in avian demographic studies is that estimates of survivorship are often biased, because they derive solely from observations of disappearance of marked individuals which may occur from either mortality or emigration. Turnover of individuals due to behavioral factors, if subsumed in the adult mortality estimate, would bias it upwards. This study asks whether the Southern California Rufous-crowned Sparrow (Aimophila ruficeps canescens) experiences reduced reproduction and survival in habitat adjacent to developed edges compared to habitat interior areas. It focuses on the relationship between territory turnover dynamics and survivorship by resighting marked individuals both on and off-plot, during the breeding and non-breeding seasons. These data in combination with reproductive data and extensive habitat measures, allows tests of assumptions about breeding history, site fidelity and dispersal. Elucidation of these relationships enables more confident attribution of territory turnover to either dispersal or mortality. The complete data set establishes a foundation for rigorously examining relationships between individual fitness, local dynamics, and landscape effects. These data would also shed light on post-breeding and natal dispersal settlement patterns, as well as the extent to which the disparate climatic conditions of the 1998 El Nino and 1999 La Nina may have affected habitat quality along edges.