Data were collected primarily by the College of William and Mary personnel, under contract with the U.S. Fish and Wildlife Service, working cooperatively with representatives from BP/CardnoENTRIX. The goal of this study was to identify osprey (Pandion haliaetus) nests that were occupied in 2010, check nests for the presence of MC 252 oil, and evaluate the number of active nests in 2011. The work plan addendum added the following goals: determine activity status of nests; count adults, eggs, young and fledging rates for all surveyed nests of breeding ospreys at Horn and Ship Islands; and compare 2011 reproductive data with pre-spill data. The objective was to estimate re-occupancy rates for osprey nests within an area of potential impact and a reference area along the northern Gulf of Mexico coast. The area of potential impact included nearshore areas from Atchafalaya Bay, LA to Apalachicola Bay, FL, and the reference area included nearshore areas from Apalachicola Bay, FL to Charlotte Harbor, FL. During the 2010 breeding season (December 2010), 30 percent of the study area was aerially surveyed to map occupied osprey nests (Rapid Assessment Aerial Survey). Then, in January and February 2011, nest material and feathers were collected from a subset of the mapped nests to assess nest and bird oiling (Rapid Assessment Ground Sampling). In the 2011 breeding season, the mapped nests were surveyed aerially to assess re-occupation rates (Reoccupation Surveys). In addition, 2011 nest activity and chick production was documented at selected nests on Horn Island and East Ship Island, MS (Productivity Survey). Additional details on the surveys and data collected under the Bird Study #9 Osprey work plan are provided in the End of Study Report (Pre-assessment of Injury to Ospreys from the Deepwater Horizon (MC 252) Oil Spill). The DWH NRDA Osprey Nest Check dataset contains the information collected during 2011 Rapid Assessment Ground Sampling and the 2011 Productivity Survey.