Population Trends in Some Florida Bay Wading Birds

Roseate spoonbills (Ajaia ajaja), Reddish Egrets (Egretta rufescens), and Great White Herons (Ardea herodias occidentalis) have unique subpopulations that are largely restricted to Florida Bay. All three species are believed to have had relatively large populations in Florida Bay, but the birds were virtually extirpated from the area between the late 1800s and the mid-1930s by human harvesting for food and feathers. After the birds were protected, they reestablished small populations that initially grew quickly. The Great White Heron population in Florida Bay increased from a low of about 20 individuals after the 1935 hurricane to a population of 800-900 resident adults in the early 1960s. As many as 400 additional birds (juveniles and possibly seasonal migrants) were present in winter censuses. The population remained at about that level through the 1960s, after recovering from a 20-40% decrease caused by a 1960 hurricane. After 1968, the population was surveyed only once, in 1984, when about the same number of birds were censused. The Reddish Egret recovered more slowly from total extirpation around 1935 to an estimated 200-250 adults in the late 1970s. Casual observations in the 1980s suggest the population has remained at about that level. Roseate Spoonbills showed an exponential recovery from just a few individuals up to a maximum of 2400 breeding birds by 1978-79. Subsequent censuses (1984-1986) revealed only about 800-900 nesting adults. The virtual absence of pre-1880s data precludes comparing present populations with those of the pristine environment. However, the most recently surveyed population of each of these species seems to be at a lower density than was historically present. The recent decline in the spoonbill population and low reproductive success of the Great White Heron population are causes for concern about the future of the populations. These findings point out the importance of continued monitoring and analysis of population trends.