BREEDING POPULATIONS AND COLONY SITE DYNAMICS OF SEABIRDS NESTING IN LOUISIANA

The Louisiana Coastal area supports a large population of colonial sea birds. For many seabird species, a significant percentage Of the Unite d States' population breeds along the Louisiana coast. We monitored th e status of seabird colonies along a portion of coastal Louisiana from 1985 to 1992. The habitats used by seabirds in our study area can be divided roughly into marsh and beach sites. Forster's Terns (Sterna fo rsteri) were found only in the marsh colonies, and Laughing culls (Lar us atricilla) were found in both marsh and beach habitats. All other s eabird species were found in beach colonies only. Population trends ar e different for each species and seem to be strongly correlated to the availability of suitable habitat. Brown Pelicans (Pelecanus occidenta lis), Royal Terns (Sterna maxima) and Sandwich Terns (Sterna sandvicen sis) have a low turnover of colony sites. These low turnover rates see m to be more related to the relative rareness Of suitable nesting site s for these species than to the stability of these habitats. Both Fors ter's Terns and Least Terns (Sterna antillarum) have relatively high t urnover rates, likely due to the instability of the nesting habitat us ed by these species. However, turnover rates of colonies in Louisiana are comparable to rates reported for colonies of the same species else where.