Deepwater Horizon NRDA Bird Study #4 focused on colonial waterbirds. The goal of this study was to evaluate spill-related injury to colonial waterbirds under the following two objectives: 1) estimate the percentage of adult and sub-adult birds that are visibly-oiled within representative breeding colonies and roosting sites throughout the study area and 2) estimate the mortality rates of both oiled and unoiled adult birds via radio and satellite telemetry. Data were collected by personnel from the Biodiversity Research Institute (BRI), under contract to the U.S. Fish and Wildlife Service, during the summer of 2010 through April of 2011. This dataset includes the Oiling Observation data collected as part of the first objective. BP personnel cooperatively participated in data collection through October of 2010. Additional details on the surveys and results pertaining to Bird Study #4 are provided in the End of Study Report (Estimating Oiling and Mortality of Breeding Colonial Waterbirds from the Deepwater Horizon Oil Spill, Bird Study #4).