Least Terns Nesting on Natural and Artificial Habitats in Georgia, USA

-Although increasing numbers of Least Terns (Sterna antillarum) are nesting on artificial substrates such as dredged-material and roofs, it is not known if these colonies are successfully fledging young. Aspects of Least Tern nesting ecology were studied in 1996 and 1997 along Georgia's coast. Numbers of nests, eggs, chicks, and fledglings at beach, dredged-material, and roof colonies were surveyed using walk-through counts from late April to mid-July. Numbers of nests ranged from 6 to 929 and they did not differ between years or among habitat types. Percent hatching success ranged from 0 to 53.4% and did not differ between years or among habitat types when the data were compared among colonies. High within-habitat type variability due to catastrophic colony failures masked differences in hatching success among habitat types. Causes of mortality included tidal flooding and human disturbance on beaches; extreme temperatures, predation by raccoons, dogs, cats, birds, and fire ants on dredged-material islands; and extreme temperatures, flooding, avian predation, and falling off roofs on buildings. More than 70% of Least Terns in Georgia are nesting with -30% hatching success on flat, gravel-covered roofs. These roofs could provide better refugia and nesting habitat if they continued to be gravel-covered rather than vinyl-covered, if drains were screened, and if -30 cm parapets were constructed around the perimeter. Received 4 May 1998, resubmitted 3 March 1999, accepted 14 April 1999.