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 know n if these colonies are successfully fledging young. Aspects of Least Tern nesting ecology were studied in 1996 and 1997 along Georgia's coast. Number s of nests, eggs, chicks, and fledglings at beach, dredged-material, and ro of 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 w ere compared among colonies. High within-habitat type variability due to ca tastrophic colony failures masked differences in hatching success among hab itat types. Causes of mortality included tidal flooding and human disturban ce on beaches; extreme temperatures, predation by raccoons, dogs, cats, bir ds, and fire ants on dredged-material islands; and extreme temperatures, fl ooding, avian predation, and falling off roofs on buildings. More than 70% of Least Terns in Georgia are nesting with similar to 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-c overed, if drains were screened, and if similar to 30 cm parapets were cons tructed around the perimeter.