This dataset was used to determine hydrologic parameters influencing Cape Sable Seaside Sparrow (CSSS) mercury exposure and potential mercury effects on their reproductive success in the Florida Everglades. We collected breast feathers for total mercury determination from juvenile and adult CSSS during (or shortly after) three breeding seasons (March 1 to July 31) and monitored the same individuals' breeding performance (mate status, number of nest attempts, number of successful nest attempts, total productivity of nests, clutch size, total count of eggs, and hatch success). Hydrologic parameters (average water depths, drought length, water recession rate, and hydroperiod) were estimated using the Everglades Depth Estimation Network and in situ depth measurements. Data collection is complete.