LTREB: Demography and Disease Ecology of a Colonial Bird

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This proposal is to continue a 25-year long study of demography and social behavior of cliff swallows in southwestern Nebraska. We will monitor survival, dispersal, and colony choice for a sample of marked birds that now numbers 158,373 individuals. This information will be applied to ongoing investigations of swallow population biology that incorporate study of the effect of group size, and will also be used to study the long-term consequences of two rare climatic events that occurred in the study area in 1996 and 2004. Severe weather of the timing and magnitude of these events has occurred in southwestern Nebraska only twice in the last 130 years. Data gathered will be applied to work on (1) the ecology and evolution of a virus associated with cliff swallows and their ectoparasites, in which we are studying how often this encephalitis-related virus is transmitted between colonies within the study area by birds, how colony use in a given year is related to prevalence of virus, whether bird movement is related to patterns of evolutionary divergence of virus subtypes within the study area, and how the virus affects survival of marked cliff swallows within and between years and thus to what degree it represents a disadvantage of living in colonies; and (2) morphological evolution and natural selection on breeding time, in which we are studying evolutionary changes in body size and extent of bilateral asymmetry in wings and tail brought about by the rare climatic events, and whether the widespread nesting failures in the 2004 breeding season will exert selection on breeding time and lead to earlier egg-laying in the population in successive generations.