Global Short Term Trend: Increase of 10-25% to decline of 30%
Comments: Within the U.S., the eastern population (Alabama, Florida, Georgia, North and South Carolina) appears to be stable and even increasing. Recent increase in North Carolina is attributed to expansion of South Carolina population, aided by creation of dredge spoil islands that provide additional nesting habitat. Gulf Coast populations are increasing steadily, but those in the U.S. Caribbean have declined over the last 10 years (J. Collazo, pers. obs.). Contaminant levels for both populations, however, are below the threshold found to induce reproductive failure [e.g., 4-5 parts per million (ppm) for DDE]. Colonies on the San Lorenzo Islands in the Gulf of California contained about 32,000 birds in 1970 but had decreased to approximately 8,200 in 1977. However, southern populations of subspecies CALIFORNICUS, occurring in Mexico, evidently are stable (D. W. Anderson, pers. comm.). U.S. Fish and Wildlife Service (1990) categorized the status of CALIFORNICUS as "stable." Data are needed on Central and South American populations where organochlorine pesticide use is still allowed. Aside from large, reproductively viable populations in Panama and Mexico, population status in Central and South America is poorly known (Crivelli and Anderson 1984, Risebrough and Schreiber 1972, Halewyn and Norton 1984, Guzman and Schreiber 1987).