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Snail Kite (Rostrhamus sociabilis) satellite telemetry reveals large-scale use of ‘peripheral’ wetlands: Implications for habitat management, population monitoring, and exposure to toxins
*KENNETH D. MEYER (meyer@arcinst.org), Avian Research and Conservation Institute, Gainesville, FL, USA. GINA M. KENT, Avian Research and Conservation Institute, Gainesville, FL, USA. KRISTEN M. HART, U.S.G.S., Davie, FL, USA. IKUKO FUJISAKI, Institute of Food and Agricultural Sciences, University of Florida, USA. AUTUMN R. SARTAIN, U.S.G.S., Davie, FL, USA. ROBERT FRAKES, U.S. Fish and Wildlife Service, Vero Beach, FL, USA. DAVID C. EVERS, Biodiversity Research Institute, Portland, Maine, USA.
The U.S. population of Snail Kites, limited to Florida, declined substantially and became federally listed as Endangered following massive hydrologic and agricultural changes to the Everglades and its headwaters. These changes to the large, naturally-functioning wetlands on which this species relies apparently had unfavorable effects on the kite’s apple snail prey. Research and monitoring based on VHF telemetry and color-banded birds have focused on these once-vast wetland systems and have assumed that Snail Kites rarely cross unsuitable habitat, even to seek refugia during droughts. Since 2007, we have collected 50,114 satellite-derived locations for 22 adult Snail Kites tagged throughout the species’ Florida range. Of these locations, 54% were outside the natural wetlands that comprise the altered remnants of the Snail Kite’s historic range. These ‘peripheral wetlands’, as they have been called, include large water-management canals, agricultural drainage ditches, neighborhood retention ponds, and storm-water treatment areas (STAs, designed to use native vegetation to reduce pollutants from agricultural run-off). None are managed specifically for Snail Kites, nor have they been regulated as suitable habitat or incorporated into the large and expensive monitoring effort devoted to this species. Agricultural chemicals may exceed safe levels. We provide results of analyses for copper, long used as a fungicide on citrus crops; and inorganic mercury, precursor to a methylated form toxic to most species of vertebrates. Sub-lethal levels of mercury (3.3-4.8 ppm) in Snail Kite samples from the southern Everglades reached concentrations known to reduce nesting success by >30% in other species of invertivorous birds. Our results indicate that the created wetlands in which Snail Kite’s spend much, if not most, of their time pose serious challenges for the management and conservation of this imperiled species.
