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We subjected nesting Black Terns (Chlidonias niger) to one of four protocols that varied in intensity of disturbance at Horicon National Wildlife Refuge, Wisconsin, in 1999. We also evaluated the efficacy of nest enclosures for obtaining reliable estimates of reproductive success for this population. We found no differences in either hatching success or fledging success among the four treatment groups. None of the 23 adults trapped on nests permanently deserted its clutch, although adults trapped before seven days of incubation generally took much longer to return to the vicinity of the nest site than did adults trapped during the latter parr of incubation. The estimated range of productivity for nests that hatched greater than or equal to one egg and were enclosed with fencing (1.56-2.25 fledglings/nest) fell within the range for nests not enclosed (1.30-2.45) and compares favorably to other estimates for this species. Although 47% of 64 nests failed to hatch chicks, most failures were attributed to inclement weather and predation. Our results indicate that intensive study of Black Terns, which involves trapping, banding and repeated nest visitations, can be conducted without detrimental impacts on reproductive success. We provide some recommendations and protocols for future work with this species.