AN INTERDECADAL COMPARISON OF POPULATION PARAMETERS OF BROWN PELICANSIN PUERTO-RICO AND THE US VIRGIN-ISLANDS

We compared selected demographic parameters between 1980-82 and 1992-9 5 of the endangered Caribbean Brown Pelican in Puerto Rico and the U.S . Virgin Islands. Mean winter counts in 1992-95 (593) were 74% lower t han 1980-82 (2,289). Mean young per successful nest was lower in 1992- 93 (1.14) than 1980-82 (1.65). DDE, PCBs and mercury levels in egg sam ples, However, were low and did nor adversely affect the species in ei ther study period. Roosting and nesting habitat losses in both study p eriods were minimal and are not believed to be limiting pelicans. The discrepancy in population counts between study periods in Puerto Rico could be cause for concern because 1990's counts were 32% (593/1840) o f the expected mean winter count for a recovered population. Long-term data (i.e., collected over six-eight years) are needed to determine t he range of acceptable demographic parameter fluctuations for Caribbea n Brown Pelicans.