Distribution and Productivity of Least Terns and Piping Plovers Along the Missouri and Cheyenne Rivers in South Dakota

Surveys were conducted in 1988 and 1989 to determine the distribution and reproductive success of least terns and piping plovers on the Missouri and Cheyenne rivers in South Dakota. All suitable habitat was surveyed, with research concentrated on two important areas: 1) the Missouri River from Fort Randall Dam to Springfield, SD, and 2) the Missouri River from Gavins Point Dam to Ponca State Park, NE. After initial surveys each colony site was searched for nests. Incubation stage was determined and nest site characteristics were recorded including: species, distance and height of nearest plant, percent vegetative cover, and distance and type of nearest object (driftwood, rock etc.). A surveyors transit and stadia rod were used to measure elevation above water for each nest. All colony sites were revisited every 7 to 10 days to determine nest fates and to search for new nests. Colony sites with successful nests were monitored to determine chick survival and fledging success. During each colony visit human, pet, and vehicle tracks, the number of nests and chicks destroyed, and evidence of other recreational activities were recorded as indicators of the type of recreational disturbance that had occurred since the last visit. The number of least terns and piping plovers below Fort Randall and Gavins Point dams decreased from 1988 to 1989. Least tern hatching success increased from 36% in 1988 to 51% in 1989 and piping plover hatching success increased from 29% in 1988 to 37% in 1989. Least tern fledging rates increased from 0~44 chicks fledged per pair in 1988 to 0.55/pr in 1989 but piping plover fledging rates decreased from 0.55/pr in 1988 to 0.26/pr in 1989. Chicks of both species fledged earlier in 1989 than in 1988. Data from this study indicates that fledging rates of least terns and piping plovers during 1988 and 1989 were too low to maintain stable populations. Primary causes of nest and chick loss were predation, flooding, weather, and human disturbance. In 1988, some level of recreational disturbance occurred on 83% of active colony sites. Posting and roping-off all colony sites, information and education efforts, and increased patrolling of colony sites by state and federal enforcement personnel proved effective in reducing recreational disturbance of colony sites in 1989