Abstract During summer, May to September, of 2005, I examined nest-site selection and breeding ecology in a mixed-species colony of Roseate Terns (Sterna dougallii), Bridled Terns (Sterna anaethetus) and Black-naped (Sterna sumatrana) Terns on the islet of Jishan, Penghu, Taiwan. The aims are to identify characteristic differences of nest sites within the habitats, and to compare nest-site preferences of early- and late-nesting Roseate Terns. Significant interspecific differrences in nesting sites were found: Roseate Terns nested in areas with short vegetation and with higher nesting densities, Bridled Terns nested on screes, and Black-naped Terns nested on flat rocky surface. Hatching success was not correlated with site variables in Roseate Terns. Site characteristics of early- and late-nesting Roseate Tern nests differed. Late-nesting terns used sites with taller vegetation, less of walls around nests, fewer neighbors within 1 m, more nests on the edge of the subcolony, and with more visibility from 2 m compared with early-nesting terns. Human picking-up the eggs and typhoon appeared to be the major mortality factor on Jishan Islet. Roseate Terns with metal bands and leg-flags have been observed in the area. The results demonstrate that Roseate Terns tend to have a fidelity to a natal colony and some migrate to Australia for wintering.