Seabirds in the saline marsh of coastal Louisiana nest on the islands that are more isolated, smaller, have lower percentages of woody vegetation, and higher percentages of herbaceous vegetation and beach habitat. Only moderate variation in these habitat features was demonstrated among years of colonization. The factors causing these preferences appear to be protection from mammalian predators and presence of suitable nesting habitat. Forster's Terns colonized islands with a lower beach percentage than those colonized by Laughing Gulls or Black Skimmers due to interspecific differences in preferred nesting substrate. Nest site tenacity was weak in that the majority (57%) of colonies was active during only one of the three years of survey. Extreme nest site tenacity is probably selected against in these highly unstable wetlands. However, those islands colonized perennially were more geographically isolated and had higher percentages of beach cover. The relationship between seabird nesting abundance and the habitat variables was low, implying a lack of fine tuning of population numbers to habitat at a local scale. Numerous islands potentially suitable for colonization by seabirds may exist along coastal Louisiana. But the presence of alternative nesting islands may be required due to the ever changing nature of these saline marsh wetlands.
