Set-Back Distances to Protect Nesting Bird Colonies from Human Disturbance in Florida

Breeding colonial waterbirds are particularly susceptible to human disturbance because of their high-density nesting habits. Identified detriments to reproductive success include egg and nestling mortality, nest evacuation, reduced nestling body mass and slower growth, premature fledging, and modified adult behaviors. Fifteen species of colonial waterbirds nesting at 17 colonies in north and central Florida were exposed to three different human disturbance mechanisms (HDMs) in order to determine recommended set-back (RS) distances for protecting these mixed-species nesting assemblages. Both intraspecific and interspecific variation were observed in flushing response distances to the same human disturbance mechanisms. In general, colonial waterbirds exhibited greater average flush distances in reaction to a walking approach than to approaching motor boats. Recommended set-back distances were estimated using a formula based on the mean plus 1.6495 standard deviations of the observed flushing distances plus 40 meters X = exp (X + 1.6495X + 40)]. In general, a recommended set-back distance of about 100 meters for wading bird colonies and 180 meters for mixed tern/skimmer colonies should be adequate to effectively buffer the sites we studies from human disturbance caused by approach of pedestrians and motor boats. We recommend follow-up studies to test our model at other breeding colonies.