Little Terns (Sterna albifrons) lay their eggs on open, sandy beaches where frequent human disturbance could decrease their nesting success. Understanding the effects of human disturbance on breeding birds is important in guiding conservation efforts in and creating management plans for natural areas. We examined the responses of Little Terns to 2 different experimental human activities: human approaches and human existence within the breeding habitats. No differences were observed in both the flight initiation distance of the birds and the length of time spent off the nests between 2 different human approaches, i.e., by 1 person vs. more than 3 people. However, when more than 3 people approached the nests, the nesting birds remained away from the nest for a longer period of time. In addition, the least tolerant distance was significantly greater for the standing observers than for the sitting observers within the breeding habitats. These results suggest that breeding Little Terns are disturbed by human activities and that buffer zones or setback areas (a minimum safe distance of nonintrusion by humans) need to be established to minimize the effects of human disturbance on breeding birds.