The snail kite (Rostrhamus sociabilis) is a small endangered raptor whose distribution in the United States is limited to the freshwater wetlands of southern and central Florida. The snail kite integrates over the entirety of the system's freshwater complex and is entirely dependent upon its aquatic resources for its existence. Because of its endangered status and dependence on the hydrologic restoration of the system, individual-based models of the dynamics of the snail kite population have been determined to be critical for assessing the success of restoration.

Earlier restoration attempts were seriously impaired over conflicting concerns regarding alternatives being considered at that time and the recovery of snail kites. The concern generated considerable support for empirical studies of dispersal and demographics of the snail kite population in South Florida. This work provides support for parameterizing the individually-based snail kite model being developed for the Across Trophic Level System Simulation model (ATLSS) being developed to assess hydrologic alternatives in the Restoration of the South Florida Ecosystem initiative. The model will concentrate on demographic and behavioral details. The proposed effort will include bio-energetic details and life-functions of individual kites evaluated on a daily time scale capable of determining the population viability of the kites over the history of the proposed restoration.

These models will provide a means of testing our hypothesis that the population responses of the kites are principally behavioral (for example, migration) for drought events of low intensity and spatial extent, but numerical (for example, changes in survival and/or reproduction) as severity and extent increase. These responses are tied integrally to the availability of the kites' forage base, the apple snail. The kites feed almost exclusively on the apple snails and are subject to the same environmental factors that influence the snails. Apple snails occur in areas of longer hydroperiods and their availability is severely reduced during drought periods.

Detailed studies on the demography and movement patterns of the kites (Bennetts and Kitchens, 1997) based on radio-telemetry and mark-resighting of banded birds, are being utilized to parameterize earlier crude models. These upgraded models will be used to estimate demography with emphasis on survival to evaluate influences of hydrologic conditions. The models will evaluate movement patterns including environmental conditions correlated with movements.

The work is currently contributing to the development of earlier an overly simple preliminary models developed within the OSIRIS framework (a modeling platform developed by Dr. Wolf Mooij of the Netherlands Institute of Ecology) into legitimately parameterized individual-based spatially explicit ATLSS models. These models will include behavioral and demographic detail and be capable of testing scenarios of hydrologic responses to manipulations of water deliveries and staging in the major wetland complexes of South Florida.

The project has been identified as a specific information need in the South Florida Ecosystem Restoration: Information Needs document prepared by the Science Subgroup of the Restoration Task Force. The proposed study provides an opportunity to quantify those impacts of hydrologic manipulations on the viability of the endangered snail kite. The critical habitat of this species, principally the Water Conservation Area landscapes and Lake Okeechobee, have been fragmented and manipulated for the last 50 years. This study should provide salient information to restoration managers for assessing restoration scenarios, particularly those that attempt to re-establish the dynamic gradient of the system and the attendant sheet flow.

Given the precarious situation of the snail kite in the United States, where it is confined solely to the South Florida ecosystem, and the fact that the species is wholly dependent on the critical functioning of the wetlands within this system for its survival, it is imperative that the model that will be used be based on absolutely sound scientific information, which can only be provided by this project.

Funding for this research was provided in significant part from the U.S. Department of the Interior South Florida Ecosystem Restoration Program "Critical Ecosystems Studies Initiative" (administered through the National Park Service) and from the U.S. Geological Survey, Florida Caribbean Science Center. Additional funding for the "Atlas Tropic Level System Simulation" was also provided by the U.S. Environmental Protection Agency and the U.S. Army Corps of Engineers.

REFERENCES

Bennetts, R.E., and Kitchens, W.M., in press, Population dynamics and conservation of snail kites in Florida: The importance of spatial and temporal scale: Colonial Waterbirds.

Bennetts, R.E., Kitchens, W.M., and DeAngelis, D.L., in press, Recovery of the snail kite in Florida: Beyond a reductionist paradigm: Transactions of the North American Wildlife and Natural Resources Conference.

(This abstract was taken from the Proceedings of the South Florida Restoration Science Forum Open File Report)