Colony site selection and abandonment by least terns Sterna antillarum in New Jersey, USA

Abstract

To develop habitat and management procedures to protect declining populations of least terns, colony site selection and abandonment by this species was investigated at 26 sites in New Jersey. Multivariate analysis was used to compare (1) colony sites to adjacent unused areas, (2) those located on beaches to dredge spoil sites and (3) abandoned to occupied colony sites. The presence of shells or pebbles in a sandy substrate, and short, sparse vegetation, were the habitat characteristics of New Jersey least tern colony sites most strongly correlated with colony site selection. Dredge spoil sites had significantly greater evidence of human disturbance, distance to water, and proportion of coarse particles in the substrate than beach sites. These differences may have contributed to the smaller colonines and greater colony turnover rates at spoil sites relative to beach sites. Overall, abandoned colony site characteristics did not differ significantly from occupied sites. However, human disturbance, over-growth of vegetation, predation, and flooding were all prevalent at colonies prior to abandonment. The results of this study suggest techniques for habitat management of both least and little terns.