LTREB: Long-term Studies of Demography and Social Behavior in a Colonial Bird

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0075199BrownThis proposal seeks support for years 20-24 of a long-term study of demography and social behavior of cliff swallows in southwestern Nebraska. The investigators will continue to monitor survival, dispersal, and colony choice for a population of marked birds that now numbers 110,286 individuals. These data will be applied to other ongoing investigations of swallow population biology that will incorporate study of the effect of group size, and will also be used to study the long-term demographic consequences of a rare climatic event that occurred in the study area in 1996. Severe weather of this timing and magnitude has occurred in southwestern Nebraska only twice inn the last 125 years, and it reduced the population of cliff swallows by over 50%. By applying the same methods and colony sampling schemes developed and used since 1982, this study will provide direct comparisons among years during a period spanning over two decades. Data gathered will be applied to work on (1) morphological evolution - directional selection on body size and selection for low levels of bilateral asymmetry brought about by the rare climatic event; (2) the relationship between colony size, steroid hormone levels, and immunocompetence - how levels of testosterone and corticosterone at different times during the breeding season vary with colony size; (3) transmission dynamics of ectoparasites and their associated alphaviruses; and (4) variation in colony size.