Pesticide Residues in Fulvous Whistling-Ducks from South Florida

Abstract

Thirty fulvous whistling-ducks (Dendrocygna bicolor) collected during 1984-85 from the Everglades Agricultural Area (EAA) of south Florida were analyzed for organochlorine and organophosphate contaminants. Contaminants were detected in 30 livers and 14 of 15 breast muscles examined. Eighteen contaminants were found. Levels of detected pesticides were below those known to pose direct threats to birds and humans; however, recent illegal use of some compounds was indicated. Sources of contamination were local but also may have been from areas outside the United States. J. WILDL. MANAGE. 53(4):1052-1057 Organochlorine and organophosphate pesticides have been used extensively for insect and rodent control on agricultural lands, and remain a source of concern relevant to impacts on wildlife resources (Fleming et al. 1983, Flickinger et al. 1986). Some of these pesticides and their metabolites are toxic, often stable in the environment, and are potentially hazardous to wildlife. For example, pesticide contamination can limit reproduction and/or survivability of waterfowl (Babcock and Flickinger 1977, Cooke 1973, White and Stickel 1975). Further, pesticide-contaminated waterfowl could pose a health risk to people who harvest and consume them. Hall (1987) stressed the need for investigations into potential wildlife reductions in regions of heavy pesticide use (i.e., agricultural areas). Due to extensive agricultural industry, the EAA in south Florida has a high rate of pesticide use. Indeed, Palm Beach County, which comprises a large portion of the EAA, uses more kg of restricted-use pesticides than any other county in Florida (Pestic. Rev. Counc. Meet., 2 Dec 1982, Exhibit 3). Rice farming and summer flooding of fallow fields in the EAA is used to control soil subsidence, insects, and nematodes, and create attractive waterfowl habitat for fulvous whistlingducks. Coincident with development of commercial rice production in the EAA, which began in 1977 (Rohrman and Alvarez 1984), the species became established as a permanent resident in south Florida (Turnbull et al. 1989). Rice culture is important to the ecology of fulvous whistling-ducks, especially during the breeding season (Bolen and Rylander 1983). However, fulvous whistling-ducks are highly se sitive to many pesticides that have been used on rice (Flickinger and King 1972, Flickinger et al. 1986). Thus, pesticide contamination is a potential source of mortality and/or reduced rep oductive success in fulvous whistling-ducks because of their close association with an intens vely farmed agricultural area. No information exists on possible pesticide contamination of waterfowl in the EAA. This information is important because of the recent establishment of a waterfowl management area in t e EAA. Our objectives were to determine p sticide levels in fulvous whistling-ducks from the EAA and determine whether levels pose a risk to the ducks or humans harvesting them. F. Montalbano, III and D. H. Brakhage provided collection assistance. D. R. Eggeman, E. L. Flickinger, and D. H. White reviewed an earlier draft of this manuscript. Appreciation is extended to D. J. Forrester for providing laboratory facilities and assistance. STUDY AREA AND METHODS Located immediately south and east of Lake Okeechobee, the EAA consists of about 305,000 ha of diked and drained Everglades habitat that were converted to agricultural production (Fig. 1). The primary crop has been sugarcane, with about 150,000 ha grown annually (Rohrman and Alvarez 1984). Since 1979, about 3,500 ha of rice also have been produced annually (Rohrman and Alvarez 1984; Fla. Game and Fresh Water Fish Comm. file data, Okeechobee). We collected 21 fulvous whistling-ducks on 15 November 1985 in an EAA rice field; 20