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10.1371/001 Table 1 Research questions, predictions from hypotheses, and statistical approaches to testing each. In environments of fluctuating resource availability, such as this, breeding dispersal may be exaggerated and not confined to individuals of low quality. We expect the decisions of all species to be mediated by the costs and benefits of fidelity, as hypothesized above, however where subdivisions are being built the adaptive decisions of sensitive species may be constrained by the rapid loss of their preferred habitats. Finally, the third question motivates a test of the hypothesis that following failure, increased number or quality of young are produced by individuals that disperse farthest or abandon mates to pursue better options, however this presumed benefit is inconsistently realized ( Table 1, 3A–3F). Additionally, we expect breeding dispersal distance to increase ( Table 1, 2B, 2C and 2F) and mate fidelity to decrease where habitats of varying quality exist near one-another because birds with poor quality territories will move to attain high quality territories ( Table 1, 2D and 2E). First, we expect reproductive failures to stimulate breeding dispersal ( Table 1, 2A) and reduce mate fidelity ( Table 1, 2E). Exploring the second question allows us to assess two more hypotheses. Investigating the first question enables us to test the hypothesis that asynchronous return to territory in species that migrate may reduce site fidelity ( Table 1 1A) and mate fidelity ( Table 1 1B) because early arriving males hedge their bets or late arriving females select mates based on territory quality rather than prior breeding experience. We organize our exploration around three research questions: 1) Does a species’ life history influence site fidelity and mate fidelity? 2) Does annual productivity, mate fidelity, or landscape conversion influence annual movement of breeders and likelihood of divorce? 3) Does movement improve reproduction or enable dispersers to settle in appropriate habitat? In so doing, we test several predictions ( Table 1) across multiple species and within a unique setting that includes forest reserves and existing developments where human actions were relatively constant during our study, as well as within forests that were actively developed into suburbs during this time. Our objective is to describe breeding dispersal and mate fidelity in a variety of songbirds that inhabit the rapidly urbanizing forests surrounding the city of Seattle, WA, USA. In urban environments breeding dispersal is rarely studied and may be influenced by the above factors as well as the actions of humans that benefit or challenge birds. Costs and benefits are affected by a rich mix of individual and environmental characteristics, including population density, territory quality, pair compatibility, success and quality of neighbors, actions of predators and parasites, and an individual’s sex, social status, age, and previous experience. Breeding dispersal in birds is generally of shorter distance than natal dispersal, often more extensive by females than males, and motivated by differential costs of movement and benefits of retaining one’s mate or territory. Breeding dispersal reflects not only an individual’s decision to remain faithful to a site, but also often its decision to remain faithful to a mate. The species that come to dominate urban systems are behaviorally flexible, which may enable them to reproduce, survive, disperse from natal areas, compete, avoid predation, and engage humans more effectively than less flexible species that are extirpated.īreeding dispersal-the annual shift in an adults’ center of reproductive activity -remains one of the least understood yet fundamental processes by which animal populations adapt to their environment. Here, general patterns of biological diversity are well known, but the adjustments of population processes leading to these patterns are understudied. Unique biogeochemical cycles, energy flows, and trophic relationships interact with altered disturbance regimes and human preferences to create a unique ecological stage in the city and its surrounding suburbs and exurbs. In an increasingly urban world, scientists are only beginning to quantify basic ecological processes that characterize the ecosystems humans call home.