- Figure 1. J. N. "Ding" Darling National Wildlife Refuge Complex, Charlotte and Lee Counties, Florida. [larger image] - Figure 2. Habitat types of J. N. “Ding” Darling National Wildlife Refuge, Florida. [larger image]

- Figure 3. Islands surveyed on Matlacha Pass National Wildlife Refuge, Florida, 20-24 September 2004. [larger image] - Figure 4. Islands surveyed on Pine Island National Wildlife Refuge, Florida, 20-24 September 2004. [larger image]

Figure 5. Locations of study sites for Hurricane Charley damage assessment, J. N. “Ding” Darling National Wildlife Refuge, Florida, 20-24 September 2004. [larger image]

JNDDNWR occupies the north central portion of Sanibel Island, Lee County, Florida (Fig. 1 and 2). Europeans populated Sanibel Island in the 19^th century with small fishing settlements and only two persons registered in the 1870 U. S. Census (Hammond, 1970). The island reportedly provided ample food in the form of wildlife and fisheries for its residents during that century, including a large feral hog population as early as 1831. Currently, most of the island's private lands (ca. 60% of island) are developed with single- and multiple-level housing and low-density commercial establishments.

At JNDDNWR, refuge personnel manage two impoundments for migratory shorebirds and waterfowl. They conduct regular monitoring of hydrological and water quality conditions in these impoundments. Staff gages have been installed and surveyed to sea level. Water level is recorded twice a month in each impoundment. Additionally, each impoundment is drawn down twice a year, once in the spring and once in the fall. They are, however, not drawn down simultaneously. The East Impoundment is lowered in March and then again in September. The West Impoundment is lowered in April and then in October. During the draw-downs, water quality is monitored in the impoundment being drawn-down and in the adjacent estuary. This is accomplished by deploying two water quality datasondes simultaneously (one in the impoundment and one in the estuary). The sondes record conductivity, temperature, pH and dissolved oxygen. Each data sonde deployment lasts 24 hours and deployments are made for draw-downs of both impoundments.

Of the four satellite refuges, three - Pine Island, Matlacha Pass, and Island Bay - were established to protect nesting waterbirds during Theodore Roosevelt's administration in 1908. Caloosahatchee NWR was established later in 1920. All of the satellite refuges provide islands of mangrove habitat, which are inhabited by a wide variety and large number of colonial nesting waterbirds. Other important habitats on the refuge islands include uplands, sand beaches, and mudflats as well as other wetland habitats. The islands also provide important waterbird resting areas adjacent to foraging habitat in the nonbreeding season.

Geomorphology and Hydrology of Sanibel Island

Sanibel Island is comprised of classical dune ridge and swale topography (Missimer, 1973, Stapor and others, 1991). These formations are clearly evident on recent aerial photographs of the island (see the right panels of Figs. 29 and 31. The hydrology of large barriers islands, such as Sanibel, is complex (Anderson and others, 2000). Only larger barrier islands, like Sanibel, have freshwater marshes in dune swales (Rheinhardt and Faser, 2001).