Patterns of colony-site use and disuse in saltmarsh-nesting Common and Roseate terns

Nearly all previous studies of saltmarsh-nesting Common Terns on the east coast of the United States have concluded that tidal saltmarshes were suboptimal or marginal breeding habitats. Questioning that conclusion, we analyzed patterns of both saltmarsh and nonmarsh colony use (stability, movement, establishment, abandonment, and size) obtained during 5 yr of annual helicopter censuses of all Common and Roseate terns breeding on Long Island, New York. We found 1900-3600 pairs at 10-33 saltmarsh and 22-30 nonmarsh sites; there were few biologically important differences between Common Terns nesting at marsh and at nonmarsh sites. We did find that (1) marsh sites and colony sizes increased through the study period; (2) both marsh and nonmarsh colonies grew with duration of occupancy; (3) smaller marsh and nonmarsh colonies (