Wolf M. Mooij¹, Julien Martin², Wiley M. Kitchens² and Donald L. DeAngelis^3
1Netherlands Institute of Ecology, Centre for Limnology, Nieuwersluis, The Netherlands
²Florida Cooperative Fish and Wildlife Research Unit, University of Florida, Gainesville, FL, USA
³U.S. Geological Survey, Florida Integrated Science Center, Department of Biology, University of Miami, Coral Gables, FL, USA

The Florida snail kite (Rostrhamus sociabilis) is an endangered raptor that occurs as an isolated population, currently of about 2000 birds, in the wetlands of southern and central Florida. Its exclusive prey species, the apple snail (Pomacea paludosa), is strongly influenced by seasonal changes in water abundance. Droughts during the snail kite breeding season have a direct negative effect on snail kite survival and reproduction; however, droughts are also essential to maintain aquatic vegetation types favorable to snail kite foraging for snails.

We used a spatially explicit individual-based model, EVERKITE, to determine how water-level temporal variation affects snail kite population viability under different temporal drought regimes in its wetland breeding habitat. EVERKITE is a spatially explicit, individual-based model designed as a management scenario evaluation tool for the endangered Florida snail kite. The model is part of the USGS Across Trophic Level System Simulation (ATLSS) program, and can be used to assess the viability of the snail kite population under different hydrologic scenarios. Specifically, the model is designed to project how hydrologic changes in the major wetlands of southern and central Florida affect the movement, reproductive success and mortality of the snail kite.

We focused on three causes of water-level variations that are likely to affect snail kites: (1) drought frequency; (2) drought duration; and (3) drought timing within the year. We modeled a 31-year historical period using four different scenarios in which the average water level is held constant, but the amplitude of water-level fluctuations is modified. Our results reveal that temporal variations in water levels affect snail kite population dynamics in a highly complex manner. Management implications of these results are discussed.

Contact Information: Donald L. DeAngelis, U.S. Geological Survey, Florida Integrated Science Center, Department of Biology, University of Miami, P.O. Box 249118, Coral Gables, FL 33124 USA, Phone: 305-284-1690, Fax: 305-284-3039, Email: don_deangelis@usgs.gov

(This abstract is from the 2006 Greater Everglades Ecosystem Restoration Conference.)

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