Open-File Report 2006-1126 i

Wildlife and habitat damage assessment from Hurricane Charley: recommendations for recovery 

of the J. N. “Ding” Darling National Wildlife Refuge Complex 

by 

J. Michael Meyers1

, Catherine A. Langtimm2, 

Thomas J. Smith III3

, and Kendra Pednault-Willett4,5 

24 April 2006 

1

 USGS Patuxent Wildlife Research Center, Warnell School of Forest Resources, The University 

of Georgia, Athens, Georgia 30602-2152. E-mail: jmeyers@smokey.forestry.uga.edu 

2 USGS Florida Integrated Science Center, Sirenia Project, 412 NE 16th Avenue, Room 250, 

Gainesville, Florida, 32601-3701. E-mail: Catherine_Langtimm@usgs.gov 

3

 USGS Florida Integrated Science Center, 600 Fourth Street, South, St. Petersburg, Florida 

33701. E-mail: Tom_J_Smith@usgs.gov 

4

 United States Fish and Wildlife Service, J. N. "Ding" Darling National Wildlife Refuge, 1 

Wildlife Drive, Sanibel, FL 33957. 

5

 Present address: Johnson Engineering, 2158 Johnson Street, Ft. Myers, FL 33901. E-mail: 

KWillet@JohnsonEng.com 
Open-File Report 2006-1126 ii

 

Executive Summary: 

• On 13 August 2004, the first of four hurricanes to strike Florida in <6 weeks came ashore near J. 

N. “Ding” Darling National Wildlife Refuge (JNDDNWR) Complex, Sanibel Island, Florida. The 

eye of Category 4 Hurricane Charley passed just north of Sanibel Island with maximum sustained 

winds of 145 mph (123 knots) and a storm surge of 0.3-2.7 m (1-9 ft). Three USGS-BRD scientists 

(coastal ecologist and research wildlife biologists) and a USFWS wildlife biologist surveyed the 

storm damage to JNDDNWR Complex on the ground from 20-24 September 2004. 

• At the request of United States Fish and Wildlife Service refuge staff, the USGS team concentrated 

on assessing damage to wetlands and habitat for selected bird populations (especially mangrove 

forests, Mangrove Cuckoos [Coccyzus minor], and Black-whiskered Vireo [Vireo altiloquus]), 

waterbird rookeries (mangrove islands), impoundments (waterbirds and waterfowl), sea grass beds 

(manatees), and upland hardwood hammocks and ridges (threatened eastern indigo snake 

[Drymarchon couperi]). 

• The refuge complex sustained moderate to catastrophic damage to vegetation, especially mangrove 

forests and waterbird nesting or roosting islands. Lumpkin Island, Hemp Island, and Bird Key 

waterbird nesting areas had >50% and sometimes 90% of their vegetation severely damaged (dead, 

broken tree stems, and tipped trees). The Shell Mound Trail area of JNDDNWR sustained 

catastrophic damage to its old growth mangrove forests. Direct storm mortality and injury to 

manatees in the area of the JNDDNWR Complex was probably slight as manatees may have several 

strategies to reduce storm mortality. Damage to seagrass beds, an important habitat for manatees, 

fishes and invertebrates, is believed to be limited to the breach at North Captiva Island. At this 

breach, refuge staff documented inundation of beds by sand and scarring by trees dragged by winds. 

• Because seagrass beads and manatee habitat extend beyond refuge boundaries (see p. 28), a 

regional approach with partner agencies to more thoroughly assess storm impacts and monitor 

recovery of seagrass and manatees is recommended. 

• Besides intensive monitoring of waterbirds and their nesting habitat (pre- and post-storm), the 

survey team recommends that the Mangrove Cuckoo be used as an indicator species for recovery of 

mangrove forests and also for monitoring songbirds at risk (this songbird is habitat-area sensitive). 

Black-whiskered Vireo may be another potential indicator species to monitor in mangrove forests. 

Monitoring for these species can be done by distance sampling on transects or by species presenceabsence from point counts. 

• Damaged vegetation should be monitored for recovery (permanent or long-term plots), especially 

where previous study plots have been established and with additional plots in mangrove forests of 

waterbird nesting islands and freshwater wetlands. 

• Potential loss of wetlands (and information for management) may be prevented by water level 

monitoring (3 permanent stations), locating the positions (GPS-GIS) and maintaining existing water 

control structures, creating a GIS map of the refuge with accurate vertical data, and monitoring and 

eradicating invasive plants. Invasive species, including Brazilian pepper (Schinus terebinthifolius) 

and air potato (Dioscorea bulbifora), were common in a very limited survey and may become more 

dominant in areas damaged by the storm. Special attention is needed to eradicate these exotic plants. 

• As an important monitoring goal, the survey team recommends that species presence-absence data 

analysis (with probability of detection) be used to determine changes in animal communities. This 

could be accomplished possibly with comparison to other storm-damaged and undamaged refuges in 

the Region. This information may be helpful to refuge managers when storms return in the future. 
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TABLE OF CONTENTS

Page 

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii 

Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Refuge mission and objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 

Geomorphology and Hydrology of Sanibel Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

 Hurricane Charley storm development and physical characteristics . . . . . . . . . . . . . . . . 5 

 Habitat damage and bird surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

 Manatees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 

 Historical characteristics of the Sanibel regional landscape . . . . . . . . . . . . . . . . . . . . . . 7 

 Vegetation surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

 History of Hurricane Charley . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

 Overview of storm’s physical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 

 Birds and their habitats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

 J. N. “Ding” Darling National Wildlife Refuge . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

 Matlacha Pass National Wildlife Refuge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

 Pine Island National Wildlife Refuge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

Manatees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

 Seagrass beds: manatee habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 

 Manatee population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 
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Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Historical comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Pre-hurricane island geomorphology, vegetation structure, and hurricane damage .. 15 

Hurricane damage to vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Regeneration following disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

 Vines, lianas, and disturbance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

 Observations of exotic plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

 Freshwater wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

Past history and future probabilities of major hurricanes in the area of Sanibel 

 Island and Port Charlotte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

 Habitat damage and effects on bird populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

 Seagrass beds: manatee habitat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 

 Manatee populations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

 Other trust species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 

Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 

Ecosystem function and refuge management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 

Birds, other trust species, and their habitats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 

Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 

Literature cited and suggested readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 

Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 
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INTRODUCTION 

 Large infrequent disturbances (LIDs), such as hurricanes, fires, floods, tornados, and 

volcanic eruptions, leave an imprint on the ecosystem and are important ecological events (Turner 

and Dale, 1998). Their ecological importance to the animal and plant community, however, is not 

well understood, but research and our understanding has increased during the last 25 years 

(Literature cited and suggested reading). LIDs have a continual lasting effect from multiple events 

that occur over long time periods. For Florida, Ball and others (1967) estimated that 160,000 to 

320,000 major hurricanes (Category 3-5) have occurred in the last 2 million years. In southern 

Florida, these storms occur every 20 or more years (Lugo and others, 1976). One of the most recent 

storms came ashore on 13 August 2004 as Category 4 Hurricane Charley at North Captiva Island and 

passed over much of the J. N. “Ding” Darling National Wildlife Refuge (JNDDNWR) Complex, 

Sanibel, FL (Caloosahatchee National Wildlife Refuge [NWR], Island Bay NWR, Matlacha Pass 

NWR, and Pine Island NWR). Within five weeks, a team of scientists was assembled to conduct 

field assessments of damage and literature searches for assisting the refuge staff with recovery. Our 

objectives for this research were to conduct an assessment of Hurricane Charley damage to wetlands 

and habitat for selected bird populations (especially mangrove forests, Mangrove Cuckoos, and 

Black-whiskered Vireo), waterbird rookeries (mangrove islands), impoundments (waterbirds and 

waterfowl), sea grass beds (manatees), and upland hardwood hammocks and ridges (threatened 

eastern indigo snake [Drymarchon couperi]). We also contacted potential collaborators and partners 

for information and possible cooperation for research on the effects of the storm. 

 Numerous reports exist concerning hurricane damage to tropical coastal ecosystems such as 

mangrove forests (Cahoon and others, 2003, Craighead and Gilbert, 1962, Doyle and others, 1995, 

Reimann, 1940, Roth, 1992, Smith and others, 1994, Stoddard, 1969), rain forests [Biotropica, 

Volumes 23(4a) and 28(4a)], freshwater swamp forests (Rybczyk and others, 1995), and hardwood 
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hammocks (Horvitz and others, 1995, Slater and others, 1995). Hurricane impacts are complex and 

range from minor damage, such as defoliation, to catastrophic blow-downs of entire stands. 

Hurricane damage, however, is much more than impacts to vegetation (Cahoon, 2003). Elevation 

within coastal marshes and forests can be changed by erosion (Jackson and others, 1995), 

sedimentation (Risi and others, 1995), formation of tip-up mounds and pits (Titus, 1990), or by postevent subsidence and compaction (Cahoon, 2003, Cahoon and others, 2003, Smith and others, 1994). 

Defoliation of the vegetation causes inputs of fresh, nutrient-rich leaves into coastal waters and 

flooding alters the sediment salinity and nutrient regime. Both can impact nutrient fluxes and water 

quality (Blood and others, 1991, Jackson and others, 1995). Disturbance to the forest canopy results 

in changed vegetation structure including shorter stature and smaller diameter stems. Importantly, 

species composition is altered, which may provide conditions for undesirable species to appear or 

increase in abundance. Vine and liana populations may increase rapidly following the loss of 

canopy trees (Allen and others, 1997, Sanchez and Islebe, 1999, Schnitzer and others, 2000). This 

period of succession can also include invasions by exotic species (Horvitz and others, 1995, 1998). 

Tip up mounds and pits created when a tree topples serve as sites for colonization and regeneration 

for both native and exotic species (Cooper-Ellis and others, 1999, Titus, 1990). Often, differences in 

storm effects are found in close proximity, depending on topography, elevations, and extent of the 

storm (Scatena and others, 1996, Walker, 1991). Hurricane Charley produced a wide variety of 

damage, short-term, and long-term effects at the JNDDNWR Complex. 

Refuge mission and objectives 

JNDDNWR Complex joins in partnership with residents of Sanibel, Captiva Islands, Lee 

County, and the State of Florida to safeguard and enhance subtropical habitat for wildlife. The 

Complex protects and provides habitat for endangered and threatened species including the west 

Indian manatee (Trichechus manatus), wood stork (Myteria americana), bald eagle (Haliaeetus 
Open-File Report 2006-1126 3

leucocephalus), and eastern indigo snake (Drymarchon couperi) as well as other United States Trust 

Species, such as Mangrove Cuckoos (Coccyzus minor) and Nearctic-Neotropical migratory birds. 

The refuge’s staff implements management techniques to sustain natural ecosystem processes and to 

provide feeding, nesting, and resting habitat for shorebirds, waterbirds, waterfowl, and NearcticNeotropical migratory songbirds. The staff also provides high quality interpretive and 

environmental education programs and recreation compatible to the purpose of the refuge (United 

States Fish and Wildlife Service, 2004). 

STUDY AREA 

JNDDNWR, the most recent of the refuges in the Complex, was established in 1945 in honor 

of Jay Norwood “Ding” Darling, a renowned editorial cartoonist, tireless conservationist leader of 

the early 20th Century, and head of the Biological Survey. The refuge covers 2,571 ha (6,354 acres) 

of estuarine, open water, sea grass bed, mud flat, impoundment, mangrove, mangrove island, 

hardwood hammock, and ridge habitats at latitude 26° 27’ N and longitude 82° 07’ W. The 

Complex (Fig. 1 and 2) includes four additional satellite refuges: Matlacha Pass NWR (Fig. 1 and 3, 

207 ha or 512 acres; 26° 40’ N, 82° 05’W), Pine Island NWR (Fig. 1 and 4, 221 ha or 548 acres; 26° 

37 N, 82° 10’W), Island Bay NWR (Fig. 1, 8 ha or 20 acres; 26° 48’N, 82° 10’W), and 

Caloosahatchee NWR (Fig. 1, 16 ha or 40 acres; 26° 42’, 82° 48’W). Approximately 44% (1,068 ha 

or 2,640 acres) of the Complex is designated as Wilderness Area (Fig 5). More than 238 bird, 51 

herpetofauna, and 32 mammal species have been identified using refuge habitat (United States Fish 

and Wildlife Service 2004). 

JNDDNWR occupies the north central portion of Sanibel Island, Lee County, Florida (Fig. 1 

and 2). Europeans populated Sanibel Island in the 19th 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, 
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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 
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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). 

METHODS 

Hurricane Charley storm development and physical characteristics. 

Descriptions of Hurricane Charley’s development, storm path, and physical characteristics 

were drawn from reports and preliminary data primarily published on the internet. Many reputable 

sources of information, such as NOAA’s National Hurricane Center (NHC), made preliminary data 

and analyses available as soon as possible to the public for research and information purposes. 

Analyses and reports presented here should be viewed as preliminary and subject to change as 

agencies and institutions finalize and publish their research after the hurricane season. Electronic 

copies of the information from web sites or unpublished reports are available from C.A. Langtimm. 

Habitat damage and bird surveys 

 We conducted field surveys of selected major habitats of JNDDNWR and the islands of 

Matlachee Pass and Pine Island NWR’s (Fig. 3 and 4), two of largest of the satellite refuges, from 20 

to 24 September 2004. The islands surveyed provide habitat for large numbers of nesting waterbirds 

from late February to July each year, but also provide resting habitat within close proximity to 

foraging sites during other times of the year. At each island or habitat, we collected data on trees 

using standard techniques for describing hurricane damage (see “Vegetation” below) (Smith and 

others, 1994 Walker, 1991). We collected a GPS position (UTM and LAT-LONG coordinates, 

NAD83) of the survey and photographed habitat at 2 to 6 recorded bearings (ca. 45° to 180° 

intervals). We also took an overstory photograph for estimating cover at the same point. These 

photographs not only provide information on damage, but will allow estimation of damage over a 
Open-File Report 2006-1126 6

much larger area using visual and other photogrammetric comparisons (i.e., locations can be found 

on aerial photographs with GPS data). Birds were noted and photographed when encountered; we 

counted endangered Wood Storks and nesting ibises and herons. Presence of exotic plants was also 

recorded and the plants were photographed. We sampled and photographed a total of 35 locations in 

15 habitats or islands, totaling 168 photographs with GPS in UTM (NAD83) coordinates and 

bearings in degrees (Table 1). Islands were sampled on the fringe and also at an interior location. 

Bird nomenclature follows the American Ornithologists’ Union (1998). 

 

Manatees 

We used several sources of data to document and describe important manatee habitat areas in 

and near the refuge complex prior to landfall of Hurricane Charley. General descriptions of manatee 

distribution patterns in the refuge complex were drawn from regional data, analyses, and figures 

provided by the Fish and Wildlife Research Institute (FWRI) of the Florida Fish and Wildlife 

Conservation Commission (Sara McDonald, personal communication). Aerial survey data were 

collected by FWRI in Lee County during twice monthly surveys in 1994-1995 and 1997-1998. Data 

were analyzed by applying a variable-shape spatial filter to make a contour map of manatee 

abundance, as described in Flamm and others, (2001). Warm and cold season distribution and 

relative abundance maps were developed for Estero Bay, Matlacha Pass (including Tarpon and San 

Carlos Bays) and Pine Island Sound. Two of these regions, Matlacha Pass and Pine Island Sound 

encompass the landscape administered by the refuge complex. 

Movement of individual manatees in these two regions was also monitored by FWRI with 

satellite telemetry. Tracking was limited to the cold season. Location data were analyzed and maps 

developed delineating “manatee corridors” used by animals to travel from one area to another, and 

“manatee places” indicative of important habitat where individuals spend extended periods of time. 
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Data from 16 animals tracked in Matlacha Pass and 12 animals tracked in Pine Island Sound are 

presented in this report in figures provided by FWRI. 

Information on cold season thermal refuges nearest the refuge complex was provided by 

Mote Marine Laboratory and FWRI, the partners collaborating with USGS Sirenia Project on the 

Manatee Individual Photo-identification System (MIPS). This program provides state-wide 

monitoring of manatees through photo-documentation of known individuals at the major winter 

aggregation sites. 

The distribution of seagrass was drawn from regional monitoring and assessment programs, 

provided by FWRI and as reported by Dawes and others (2004). An assessment of the degree of 

scarring of these beds by boat propellers was based on a technical report published by FMRI 

(Madley and others, 2004). 

Data are few on the direct impact of the hurricane on manatees and manatee habitat. 

Observations of damage to seagrass beds during aerial surveys by refuge personnel and monitoring 

by Mote Marine Lab are described. We further identify those areas in the refuge complex with the 

greatest likelihood of impact by comparing the path of the core of the storm with pre-hurricane 

distributions of primary habitat and manatee high use areas. We then project possible short-term and 

long-term impacts to habitat and manatees based on principles of biology and findings from previous 

research at other locations. 

Historical characteristics of the Sanibel regional landscape 

After our field surveys, we acquired historical topographic sheets for the Sanibel – Captiva – 

Pine Island area, which were prepared by the United States Coast and Geodetic Survey from 1857-

1867. These sheets are not rectified or geo-referenced at this time. Some features, however, are 

visible on the 19th Century sheets, when compared with the same areas on recent false color infrared 

aerial photographs (1999). Specifically, we determined if the rookery islands of interest to refuge 
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staff were present on the historic sheets and we compared other specific areas of interest, such as the 

Shell Mound Trail area. 

Vegetation surveys

We conducted qualitative (visual) and quantitative vegetation surveys in a variety of habitats 

at 15 areas of JNDDNWR Complex. Mangrove forests comprise the majority of forested habitat on 

the Complex; therefore, more surveys were conducted in these forests. We surveyed and sampled 

mangrove forests at Shell Mound Trail, Power Line easement (road), Legion Curve, Givney Key, 

Upper and Lower Bird Islands, Bird Key, Hemp Island, Lumpkin Island, East and West 

Impoundments, and along Dixie-Beach Boulevard (see Figs. 3, 4, and 5 for island and study 

locations). Hardwood hammocks were examined at Shell Mound (Fig. 5), along the Legion Curve 

(west side of Indigo Trail) and at Hemp Island (Fig 4.). We took numerous photographs and 

recorded notes at all sites. We recorded damage and mortality (by species), size (diameter at breast 

height [dbh] in cm) and direction of fall in plots of known area at several locations. No stems were 

permanently tagged for future reference although the locations of the plot were recorded in latitudelongitude (degrees to 5 decimal places) and UTM (NAD83) using GPS. In addition, we surveyed 

four mangrove forest plots (vegetation) that had been established by the Sanibel-Captiva 

Conservation Foundation Marine Laboratory (SCCF) prior to the passage of Hurricane Charley 

(plots 5 and 6, near JNDDNWR’s West Impoundment and plots 7 and 8, along Dixie-Beach 

Boulevard). 

We made observations concerning the potential for vegetation communities to recover. This 

included noting the presence or absence of seedlings and/or sapling-sized individuals at all sites. We 

examined damaged individuals to see if they were coppicing or stump sprouting (the production of 

adventitious shoots from the main trunk or stump). Special attention was given to vines and lianas, 

both native and exotic, as they can respond to disturbance very quickly. 
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Following our field work at JNDDNWR Complex we conducted literature searches to 

compile lists of potential invasive exotic species which could become of management concern in the 

future. Botanical nomenclature follows Nelson (1996) and Wunderlin (1998).

RESULTS 

History of Hurricane Charley

 Hurricane Charley was the third named tropical storm to develop in the North Atlantic in 

2004 and the first of four major hurricanes to impact Florida in less than a six week period. It was 

the first major hurricane to impact Sanibel Island in more than 40 years. A summary of the history 

of storm development and its path was provided after the storm by NOAA’s National Hurricane 

Center (http://www.nhc.noaa.gov/2004charley.shtml; 13 June 2005). Charley originated from a 

tropical wave, which developed into a tropical depression just east of Barbados on 9 August. It 

moved quickly west-northwestward across the Caribbean and strengthened to a hurricane on 11 

August as it passed south of Jamaica. Then, it turned toward the north-northwest passing over 

western Cuba with Category 3 winds of 105 knots. It weakened somewhat over the lower Straits of 

Florida while turning northward to the Dry Tortugas. From there, Charley turned toward the 

southwest coast of Florida. Contrary to forecasts, just prior to landfall it made a sudden turn to the 

east and intensified rapidly to a Category 4 storm. The eye of Hurricane Charley made landfall on 

the southwest coast of Florida near Cayo Costa, Lee County, just north of Captiva Island at 

approximately 15:45 EDT 13 August (Fig 1). Maximum sustained winds were tentatively estimated 

at a devastating 130 kt – a Category 4 out of 5 on the Saffir-Simpson scale. The hurricane traversed 

the Northern Charlotte Harbor, coming ashore again at Port Charlotte. It then traversed the central 

Florida peninsula, moving off the northeast coast of Florida near Daytona Beach, still with hurricane 

force winds. After moving into the Atlantic, Charley came ashore again near Cape Romain, South 

Carolina. The center then moved just offshore and made a third landfall at North Myrtle Beach with 
Open-File Report 2006-1126 10

winds near 70 kt. Charley remained over land where it weakened and became extratropical. Its 

remnants finally were absorbed by a frontal zone near southeastern Massachusetts. 

Overview of storm’s physical characteristics 

Hurricane Charley was an intense, compact, swift moving storm. Figure 6 presents wind 

speeds within the hurricane at landfall from a surface wind field analysis provide by the NOAA 

Hurricane Research Division of the Atlantic Oceanographic and Meteorological Laboratory 

(http://www.aoml.noaa.gov/hrd/Storm_pages/charley2004/wind.html, 18 Aug 2004). As can be seen 

from the graphic, the eye of the hurricane at landfall may only have been 8-10 km wide (5 or 6 

miles). Maximum observed surface wind speeds of 123 kt occurred 5 nautical miles SE of the eye; 

the extent of the most intensive and destructive winds was small. The path of the storm brought the 

core of the hurricane force winds to bear on North Captiva and Captiva Islands, producing an ocean 

breach on North Captiva at its narrowest point (Fig. 7). The intense core then proceeded northeast 

impacting the mangrove islands at the north end of Pine Island NWR in Pine Island Sound and, after 

crossing over the northern segment of Pine Island, hitting the northern mangrove islands of Matlacha 

Pass NWR. Charley then moved northeast into Charlotte Harbor and inland across Florida. 

JNDDNWR on Sanibel Island received less damage than the Captiva Islands as it was further south 

and east of the eye and core. 

Although it produced intense surface winds, only a small storm surge accompanied the storm 

as it made landfall in the area of the JNDDNWR Complex. Figures 8 and 9 present initial data on 

the observed storm surge from on-site visits by the Coastal High Water Study Team under the 

Federal Emergency Management Agency (FEMA). The highest levels occurred seaward along the 

path of the intense core of the storm – North Captiva and Captiva Islands (Fig. 8). Behind the 

barrier islands, the storm surge was lower (Fig. 9), but again the highest surge was along the path 

southeast of the storm’s eye – at the shoreline of the north segment of Pine Island. Storm surge 
Open-File Report 2006-1126 11

heights, however, were relatively modest at 4-9 ft (1.2-2.7 m) at their highest point. Brian Jarvinen, 

storm surge specialist with the National Hurricane Center, reported that forecasters originally 

predicted a storm surge of up to 18 feet or 5.5 m (J. Thompson, St. Petersburg Times, 17 August 

2004). As the storm approached the coast, however, it intensified from a Category 2 to Category 4 

hurricane, increased its forward speed to 25 mph (40 kph), and the core of the hurricane force winds 

shrank from 24 to 10 miles (38 to 16 km) across. A lower than expected storm surge resulted due to 

a small zone of winds capable of producing a storm surge, the fast speed that lessened the build up of 

water ahead of the storm, and the low tide at the time of landfall. 

Birds and their habitats 

J. N. “Ding” Darling National Wildlife Refuge 

 Based on our limited surveys, hurricane damage to habitats in this refuge ranged from 

moderate to severe and catastrophic (Figs. 10 and 11). Older and taller (~10 m) mangrove forests 

may have sustained more severe damage than mangroves with less stature. Live oak hammocks 

sustained moderate damage (mostly broken limbs) with rare occurrences of uprooted or snapped 

trees (Fig. 12). Impoundment aquatic habitat and sea grass beds in the refuge estuary appeared to 

have only slight to no damage. Wading birds foraged in fairly large numbers (25-50) in 

impoundments and estuary sea grass beds at low tide during our field survey on 22 September 2004 

(Fig. 13). Based on our surveys, most of the severe to catastrophic damage occurred on the 

northwestern side of the refuge, especially at Shell Mound Trail and next to the powerline rights-ofway areas, which were closer to the eye of the storm (Table 1). 

Matlacha Pass National Wildlife Refuge 

 Lumpkin Island. Hurricane Charley caused severe to catastrophic damage to vegetation on 

the island (Fig. 14). Upon entry to the island’s interior, we located nests of night herons (Nycticorox 
Open-File Report 2006-1126 12

sp. unknown) and one nestling <14 days old (~35-40 days after eggs were laid, Baicich and 

Harrison, 1997). We also observed juvenile White Ibis (Eudocimus albus) ca. 4-5 weeks old (almost 

fledged), which means eggs were first laid 49-56 days previously or about 8 to15 days before the 

storm. 

Upper Bird Island. This small rookery island sustained moderate damage from Hurricane 

Charley (Fig. 15). The island contained mangroves and limited upland habitat, covered in dense 

shrub-scrub habitat with patches of grasses and bare sand. Most of the trees and shrubs had leaves, 

but the island’s edge sustained moderate damage from wind and waves. Birds were not observed 

roosting on the island. 

Givney Key. We found moderate storm damage to vegetation on the island with ca. 50% 

leaf cover remaining on shrubs and mangroves (Fig. 16). We also observed more than 20 White 

Ibis nests in low shrubs on the island. Twelve nestlings, estimated at 3-5 weeks old, were observed 

in the shrubs or on the ground near the nests, which indicates that nests and eggs survived the storm 

(see Lumpkin Island, above). 

Lower Bird Island. Upon close approach to the island we observed moderate damage, 

mainly loss of leaf cover in sections of the island (Fig. 17). We found moderate damage, i.e., 

snapped trees and loss of leaf cover upon entering the island (Fig. 18). The interior of the island was 

covered by water. When we entered this area, we flushed 10-12 Black-crowned Night-Herons 

(Nycticorax nyticorax) from dense mangroves, but we did not find any active nests, such as those 

found on other islands. 

Pine Island National Wildlife Refuge 

 Bird Key. This active waterbird area in Pine Island Sound sustained catastrophic damage 

to vegetation and nesting habitat (Fig. 19). Most of the canopy trees snapped or tipped in the storm. 
Open-File Report 2006-1126 13

Little to no leaf cover remained on shrubs and trees. Waterbirds were using the Key for resting just 

prior to our survey. 

Hemp Island. We found catastrophic damage to vegetation and nesting habitat on this 

island, similar to the damage found on Bird Key (Figs. 20 and 21). On 24 September 2004, we saw 

large numbers (100’s) of waterbirds resting on island, which is located 6.1 km west of North Captiva 

Island and 2.4 km from Pine Island in Pine Island Sound. While measuring damage to vegetation, 

we also recorded 11 Wood Storks leaving the island (Fig. 22). 

Manatees 

Seagrass beds: manatee habitat 

Seagrass beds are important foraging habitat for manatees (Best, 1981, Lefebvre, 2000, 

Lefebvre and others, 2001) and cover substantial areas of Pine Island Sound, Matlacha Pass, and San 

Carlos Bay (Fig. 23), primarily in the shallow depths of the waterways (<1-6 ft [<0.3-2 m] Fig. 24). 

Most of the islands of Pine Island NWR, Matlacha Pass NWR, and Island Bay NWR are surrounded 

by or adjacent to seagrass beds. JNDDNWR waters also include significant seagrass beds. As of 

1995, large sections of seagrasses in Lee County were rated as degraded with light to severe scarring 

from propeller cuts of boats operating in the shallow waters (Madley, and others, 2004, Sargent, and 

others, 1995). Areas of scarred seagrass were scattered throughout the region. 

The track of Hurricane Charley took the most destructive forces of the hurricane over North 

Captiva Island (Fig. 6) and across the northern sections of Pine Island Sound, Matlacha Pass, and 

into Port Charlotte. The worst damage to seagrass appears to have occurred at the breach on North 

Captiva. Wind and waves eroded sand into the sound burying the seagrass adjacent to the island 

(Fig. 25). Dr. Brad Robbins, Mote Marine Laboratory (pers. comm.), visited the area after the 

hurricane and estimated approximately 1 ha (~2.5 acres) of seagrass was lost due to the breach. 

Refuge personnel documented additional localized damage. Scarring occurred as wind and waves 
Open-File Report 2006-1126 14

dragged many dislodged trees from the breach across the seagrass beds scouring the vegetation from 

the substrate. Sand inundation and scars from tree drags are clearly seen in aerial photos (Fig. 25). 

This area, however, has been repeatedly eroded by storms and undoubtedly will be again. Prior to 

the breach at North Captiva Island from Charley, two smaller channels were opened in the same area 

in 2001 from Tropical Storm Gabrielle (USGS Coastal & Marine Geology Program, Hurricane and 

Extreme Storm Impact Studies http://coastal.er.usgs.gov/hurricanes/charley/index.html, 16 Oct 

2004). 

Manatee population 

Examination of aerial survey data from the late 1990s (Fig. 26) shows that during hurricane 

season the highest concentrations of manatees within the refuge complex occur in Tarpon Bay and 

around Buck Key in JNDDNWR; near Chino Island in Pine Island NWR; and near Big Island and 

Fisherman Key (San Carlos Bay), Manatee Bay, Master’s Landing, McCardle Island (Matlacha 

Pass), and Bull Island and Brown Pelican Island (north of Matlacha Bridge) in Matlacha Pass NWR. 

Low abundances of manatees are seen along the west edge of Pine Island Sound with only a few 

animals found along the eastern edge. By far the greatest numbers of manatees occur throughout 

areas of Matlacha Pass and San Carlos Bay. The distribution of manatees (Fig. 13) correlates fairly 

well with the distribution of seagrass (Fig. 23). The low number of sightings along the east edge of 

Pine Island Sound is probably a factor of low water levels preventing manatees from easily feeding 

on the seagrass there (Fig. 24). The area where the breach occurred at North Captiva Island was 

characterized as a low-use manatee area prior to the hurricane. Within the cold season the 

distribution patterns are similar with the exception of fewer manatees sighted in Pine Island Sound 

(Fig. 27). A similar pattern is seen from the telemetry data (Fig. 28). 
Open-File Report 2006-1126 15

Vegetation 

Historical comparisons 

All seven of the islands used by nesting waterbirds that we visited appear on the 19th Century 

topographic sheets of the region. Although the islands were initially protected because of their 

nesting birds in the early 1900s, we wanted to be sure that they were not the result of dredging 

operations. In particular, the Bird Islands (both upper and lower) and the Tarpon Bay Keys, had an 

appearance of being spoil islands. Examination of the topographic sheets, however, showed that this 

was not the case. The Tarpon Bay Keys are clearly apparent on Sheet #T-693 (Fig. 29). Bird Key is 

clearly indicated also on sheet #T-738 (Fig. 30). The other rookery islands also appear on these 

early maps. This does not mean necessarily that the islands have not changed over time, or that they 

have not been impacted since the advent of dredging. 

Another interesting comparison is that of the Shell Mound Trail – Power Line Road – West 

Impoundment area of the refuge (Fig. 31). The open water shoreline of the impoundment appears 

unchanged, yet some other water bodies have clearly changed over time. Additionally, there is 

evidence of vegetation change with the possible infilling of a coastal marsh by mangrove forest 

vegetation (Fig. 31). Determining all of the changes from the 1857 charts to present is beyond the 

scope of this report. 

Pre-hurricane island geomorphology, vegetation structure, and hurricane damage 

We used the descriptions for mangrove forests first proposed by Lugo and Snedaker (1974) 

and used by Odum and others (1982) in their south Florida mangrove forest community profile. The 

waterbird breeding islands fall into three, broad, categories: overwash forests, fringe forests and 

basin forests. Several islands have more than one type of mangrove forest present. Tarpon Bay 

Keys are low in elevation and are inundated at high tide. Therefore, these are overwash islands 

dominated by red mangrove (Rhizophora mangle) trees. Lower Bird Island is relatively small (<1 
Open-File Report 2006-1126 16

ha). It has fringe mangrove forests around its perimeter. The interior of this island is a slightly 

elevated open area, with woody vines (e.g., nicker bean, Caesalpinia spp.) and exotics (e.g., 

Brazilian pepper, Schinus terebinthifolius). 

The remaining four islands are more complex and have higher elevation areas that lie well 

above mean high tide. Areas with higher elevations support native and exotic plants. Bird Key, 

Givney Key, Hemp Island, and Lumpkin Island are fringed by red mangroves, just inland of which 

lies an elevated berm. These berms have both tropical hardwood species (e.g., gumbo limbo, 

Bursera simaruba) and invasive exotic plants (e.g., Brazilian pepper) growing on them. Interiors of 

these four islands are typical basin-type mangrove forests (Table 2). The presence of these basin 

mangroves sets these islands apart from the others. Basin mangroves are poorly drained and thus are 

often flooded for long periods of time. On these islands, we found fine to course forest soils with 

shell hash and high organic matter content (T. J. Smith, personal observation). These interior basin 

forests were dominated by the black mangrove (Avicennia germinans), with red mangroves abundant 

only on Lumpkin Island, while the white mangrove (Laguncularia racemosa) was uncommon 

throughout (Table 2). Hemp Island was further differentiated from the others by the presence of a 

very high (≈ 20 ft or 6.1 m above msl) mound that formed a partial ring around the western side of 

the island. This mound was covered in a tropical hardwood hammock dominated by gumbo limbo 

with an understory of Jamaica dogwood (Piscidia piscipula). A large gumbo limbo had been tippedup revealing that the mound is in fact a shell midden, probably dating to the Calusa culture (Walker 

and others, 1998). Two exotic plant species, both indicative of white settler habitation, lily and 

papaya, where also present at this location (Fig. 32). 

An interesting feature of Hurricane Charley was that it was fast moving and did not have a 

large storm surge (Figs. 8 and 9). We found evidence of overwash and sediment deposition on two 

waterbird islands, Upper Bird Island and Givney Key (Fig. 33). It appeared, however, to be very 
Open-File Report 2006-1126 17

limited in extent. Overall, there appeared to be little evidence of sediment having been carried into 

the interior of the islands. 

Hurricane damage to vegetation 

Vegetation damage ranged from simple salt burns on plant leaves; to loss of leaves and some 

branches through heavy defoliation, crown damage and some windthrow; to almost complete loss of 

the forest canopy with high tree mortality (Fig. 34). In general, we observed the most severe damage 

in mangrove forests and least severe damage in live oak, cabbage palm, and tropical hardwood 

hammocks. Damage also appeared to be least in the southern portions of the Complex and increased 

northward towards the location where the eye of Hurricane Charley crossed the coastal barrier 

islands. Our quantitative data support this view (Table 2). We measured the greatest damage on 

Bird Key where the basin forest had 60-90% tree mortality. In geomorphologically similar forests 

on Givney Key, mortality approached only 20% (Table 2). Data from the SCCF mangrove plots (4) 

also showed these trends (E. Milbrandt, unpublished data). 

The area of the Shell Mound Trail – Power Line Road deserves a special comment (Fig. 31). 

The mangroves in this area appeared to be what Lugo (1997) termed “old growth” forest. This is an 

unusual and rare form of mangrove forest. The trees are quite large in diameter and height and stem 

density is low. The canopy is dense and there is little or no understory, which means there is no pool 

of seedling or sapling-sized individuals. Our observations in this area indicated that all of these 

characteristics were present prior to Hurricane Charley. Unlike the waterbird islands where black 

mangrove was dominant, the Shell Mound Trail forest was dominated by very large red mangroves 

(≈ 30 to 50 cm dbh), with large black and a few white mangroves, scattered throughout. The forest 

canopy in this area was catastrophically damaged. Mortality of canopy-sized individuals was in the 

range of 80-100%. 
Open-File Report 2006-1126 18

Regeneration following disturbance 

Many plants have the ability to regenerate vegetatively following disturbance. This is 

especially true for plants of tropical origin; however, species differ in this ability. For example, the 

red mangrove can’t coppice or stump sprout (Smith and others, 1994). Black mangroves, however, 

can (Fig. 35). Tropical species such as gumbo limbo and sea grape also resprout very quickly 

following disturbance (Fig. 35). 

Another factor affecting forest recovery is advance regeneration. This refers to the presence 

of seedling and sapling-sized individuals in the forest at the time of disturbance. These individuals, 

which are already present, form the pool from which the new forest canopy develops. We observed 

advance regeneration at many mangrove forests, but not all (Fig. 36). In particular, the Shell Mound 

Trail – Power Line Road forest was devoid of advance regeneration. 

Hurricane disturbance creates a variety of micro sites within the vegetation for regeneration 

that had not been present prior to the storm. New light regimes exist and the topography of the 

forest floor is altered by tip-up mounds and pits. Tip-ups were present in all forests we visited (Fig. 

37), but appeared to be most abundant in the basin forests of waterbird nesting islands. Tip-ups are 

especially important in mangrove forests. Here they provide regeneration sites for species not 

normally encountered in these forests. We found many tip-ups with non-mangrove species 

regenerating on them (Fig. 38). Following Hurricane Andrew, tip-up mounds in mangroves were 

extensively colonized by invasive exotics such as Brazilian pepper, papaya, and lather leaf (T. J. 

Smith, personal observation, see also Table 3). 

Vines, lianas, and disturbance 

We encountered vines at every site we visited, including Upper Bird Island, the smallest of 

the waterbird islands. The most common vine we found was nicker bean, a native species (Fig 39). 
Open-File Report 2006-1126 19

We also found Virginia creeper, poison ivy, devils claw, grapes, morning glories, and mangrove 

rubber vine (Table 3). Interestingly, we did not encounter coin vine, which is common in mangrove 

forests of Everglades National Park. This is most likely a result of limited surveys rather than true 

absence. Finally, we found a very aggressive, invasive exotic vine, air potato, at two locations, Shell 

Mound Trail and near Legion Curve (Fig. 39). We learned that another invasive vine, rosary pea, 

was present on the refuge, although we did not observe it during our visit. 

Observations on exotic plants 

Numerous exotic plant species were encountered during our surveys (see above and Table 3). 

The most abundant exotic plant on the waterbird islands was Brazilian pepper. On several islands 

we found wading bird nests in Brazilian pepper plants (Fig. 40). The most problematic exotic we 

encountered is the vine, air potato (Fig. 39). This species is extremely aggressive and can spread 

rapidly. It has the capability to become established along the edge of a wetland and then spreading 

over the wetland using the native plants for support, like a trellis. Other invasive vines also can do 

this, particularly lather leaf (Table 3), which is a problem in coastal regions of Everglades National 

Park. 

Freshwater wetlands 

We did not survey freshwater wetlands which are present on JNDDNWR (Fig. 41). There 

may be, however, evidence of human activities that have altered the surface hydrology of the refuge 

in the past (besides the waterbird impoundments). The Shell Mound Trail – Power Line Road area 

mangroves appear particularly to have been impacted (see Fig. 5 and 31 for location). We found 

several water control structures along Power Line Road (Fig. 42). It appears, from our one 

observation, that freshwater was being impounded to the west of Power Line Road. This high water 

may be another factor that contributes to the lack of advance regeneration in the mangrove forests 
Open-File Report 2006-1126 20

from Power Line Road westward to Shell Mound Trail. Mangrove propagules and seedlings cannot 

become established in standing water; they require tidal dry-downs (Smith, 1992). 

DISCUSSION 

Past history and future probabilities of major hurricanes in the area of Sanibel Island and 

Port Charlotte

The area in and around JNDDNWR Complex is hit periodically by tropical storms and by 

minor and major hurricanes (Category 3-5). The landscape has repeatedly been sculpted by wind 

and waves from tropical cyclones. Prior to Hurricane Charley, three major hurricanes occurred in 

the area since 1900. The Great Miami Hurricane of 1926 first devastated Miami as a Category 4 

storm then passed over San Carlos Bay and Captiva Island as a Category 3 storm. In 1944, an 

unnamed Category 3 storm passed west of the area making landfall near the Sarasota County line. 

The last major hurricane to impact the area was in 1960 when Hurricane Donna took a storm track 

similar to Charley. Donna made landfall as a Category 4 Hurricane near Naples and cut a path north 

to Ft. Myers and across the peninsula to re-enter the Atlantic Ocean near Daytona Beach. The storm 

track of the eye of Donna was east of the Complex, but the size of the storm was immense, and the 

Charlotte harbor area was subjected to hurricane force and greater winds for over four hours (Dunion 

and others, 2003). 

The relative inactivity of hurricane-status storms since Donna has been due to a larger global 

climate pattern. Hurricane activity in the western Atlantic is known to occur in multi-decade cycles 

that alternate between active and quiet phases of 25-40 years each (Gray 1990, Landsea 1993). In 

1995, we entered a new cycle of increased activity that is expected to continue for the next 20 to 40 

years (Landsea and others, 1996). Global warming is not expected to alter this multi-decade cycle, 

but a recent analysis concludes that it will likely result in hurricanes of higher intensity and 
Open-File Report 2006-1126 21

precipitation rates than experienced in the past with a greater risk of occurrence of highly destructive 

Category 5 storms (Knutson and Tuleya, 2004). 

Habitat damage and effects on bird populations 

Hurricanes have direct and indirect effects on birds (Wiley and Wunderle, 1993). The 

storm’s direct effect kills birds (Hooper, 1990, Meyers and others, 1993, Semple, 1936) or displaces 

them 1,000’s of kilometers from their original home ranges (Chapin, 1934). Bird mortality in the 

short-term, caused by indirect effects from storms, can be precipitated by a loss of food supplies, 

foraging substrates, nesting and roosting sites, or from increases in predation, conflicts with humans, 

and changes in microclimate (Cely, 1991, Hooper and others, 1990, Waide, 1991a ,1991b, Wiley 

and Wunderle, 1993, Wunderle ,1995). Seed, fruit, and nectar feeding birds may suffer the most, 

immediately after the hurricane (Askins and Ewert, 1991, Waide, 1991a, 1991b, Wunderle and 

others, 1992, Wiley and Wunderle, 1993). More than 87% of 1,765 Red-cockaded Woodpecker 

(Picoides borealis) cavity trees were lost in South Carolina during and after Hurricane Hugo 

(Hooper, 1990). Positive impacts on bird populations also occur. Many insectivorous and 

omnivorous birds increase after hurricanes and may be adapted to storms by the plasticity of their 

diets and habitat requirements (Waide, 1991b), but some investigators suggest that birds move away 

temporarily (Askins and Ewert, 1991). Lost of foraging habitat could cause birds to move 

elsewhere, especially in winter. Wunderle and others (1992) found large declines of wintering 

Black-and-white Warblers (Minotilta varia) in Jamaica after Hurricane Gilbert, which was probably 

related to large losses of tree trunks for foraging. We expect similar effects on birds at JNDDNWR 

Complex from Hurricane Charley. 

Birds may also shift and adapt to storm damage, e.g., by feeding in different habitat (canopy 

birds feeding in understory, Wunderle, 1995) or by building nests on fallen debris (e.g., Brown 

Pelicans [Pelecanus occidentalis], Pierce, 1990) or at new locations nearby (Cely, 1991). We expect 
Open-File Report 2006-1126 22

Brown Pelicans at JNDDNWR Complex to build nests on damaged habitat and successfully rear 

their young given that fish populations in the area have not been impacted negatively and that spring 

high tides do not destroy nests. Erosion of pelican nesting islands during Hurricane Hugo and loss 

of nesting substrate on three islands in South Carolina caused failure of most of the 3,000 nesting 

pelicans a year after the storm because of lower nesting substrate and a high tide in late May (Marsh 

and Wilkerson, 1991). Increased numbers of nesting pelicans, however, arrived shortly after that 

destructive high tide event at a nesting area 45 km to the SW, which was unaffected by the 

Hurricane Hugo storm surge and spring high tides. Pierce (1990) found that Brown Pelicans learned 

to build nests on damaged habitat or fallen debris and actually increased the number of fledglings the 

year following Hurricane Hugo. We expect pelicans at JNDDNWR Complex to also successfully 

maintain their breeding colonies. Site fidelity is strong for this species based on years of experience 

with construction related habitat changes and continual increases of nesting pairs (from 2 to >300 

pairs) in Mobile Bay, Alabama (J. M. Meyers, personal observation and unpublished data). 

Only one Bald Eagle nest was reported lost at JNDDNWR Complex (K. Pednault-Willett, 

personal observation). Bald Eagles rebuilt 21 of 24 destroyed nests at their original nesting territory 

after Hurricane Hugo (Cely, 1991). We would expect eagles nesting at the complex, which have lost 

nests, to rebuild within the same area, although the nest may be built in shorter trees or man-made 

objects. 

Bird population declines from storms over the long-term may be caused by loss of habitat, 

but habitat usually recovers with plant succession. Forest interior birds may be absent for 1-2 years 

in former forest habitat after a storm (e.g., 17 mo after Hurricane Joan in Nicaragua, Wiley and 

Wunderle 1993). The bird community changes in this situation, to one associated with edge and 

second growth (shrub-scrub) habitat until forest structure develops. An exception to this type of 

recovery would be severe to catastrophic hurricane damage to old growth forests where recovery 

may take from decades to a century (Hooper 1990, Wiley and Wunderle, 1993). Some bird 
Open-File Report 2006-1126 23

populations may decline in old growth mangrove and oak hammock habitats of JNDDNWR 

Complex, especially those habitats with severe to catastrophic impacts from the storm, e.g., major 

losses of tree canopy from tree snaps and tips. Monitoring species richness and abundance will 

provide valuable information on recovery from the hurricane as well as benefiting the refuge’s 

mission and management goals. Methods that account for differences in species detection 

probabilities will provide better estimates of population and community changes (Buckland and 

others, 1993, Boulinier and others, 1998, Hines and others, 1999, Nichols and Conroy 1996; Nichols 

and others, 1998a, 1998b). Residents, such as the Mangrove Cuckoo, and migrants, such the Blackwhiskered Vireo or other high priority Nearctic- Neotropical migrants (see Rich and others, 2004) 

should be the focus of monitoring. Monitoring for these species can be done by distance sampling 

on transects or by species presence-absence from point counts. 

Waterbird breeding colonies in slightly damaged nesting habitat from Hurricane Hugo, 

showed quite different results in breeding after the storm passed over Pumpkinseed Island, South 

Carolina (Sheppard and others, 1991). White Ibis (Eudocimus albus) breeding pairs in one colony 

declined from 10,000 pairs to zero after the storm. Although ibises were in the area, they failed to 

initiate breeding and may have moved south. There was, however, evidence that freshwater 

wetlands used by feeding ibises were modified by saltwater intrusion caused by a high storm surge. 

Nesting White Ibis in the JNDDNWR Complex will probably continue nesting there if freshwater 

feeding areas were not inundated by saltwater. We expect that a minimum of damage occurred to 

freshwater feeding areas because of a relatively low storm surge from Hurricane Charley. 

Nesting Great Egrets (Ardea alba) and Tricolored Herons (Egretta tricolor) declined at 

Pumpkinseed Island colonies affected by Hurricane Hugo. Nesting Great Egrets declined 44% 

because of nesting habitat loss (marsh elder, Iva frutescens). This species also did not change its 

average nesting height after the storm. On Pumpkinseed Island, Great Egrets showed site fidelity by 

nesting on damaged habitat, but some may have moved 7 km south. This will probably also occur at 
Open-File Report 2006-1126 24

JNDDNWR Complex in 2005 with some waterbird colonies nesting on damaged habitat, at lower 

heights, or even on the ground while other colonies may shift to new nesting areas, if available 

nearby. Nesting on the ground will probably increase mortality from high spring tidal overwash, 

which caused an 86% abandonment rate of Snowy Egret (Egretta thula) nests after Hurricane Hugo 

in South Carolina (Shepherd and others, 1991). About 80-90% of all Snowy Egrets nested on the 

ground a year after Hurricane Hugo with few nests surviving overwashes that year. Pierce (1990, 

1991) reported loss of breeding for one year at Red-footed Booby (Sula sula) colonies in the Virgin 

Islands after Hurricane Hugo; however, Sooty Tern (Sterna fuscata) colonies increased in breeding 

pairs in the same area. Saliva (1989) also reported loss of waterbird nesting habitat (loss of rocks or 

vegetation) and nesting waterbirds on the Culebra Islands, Puerto Rico, but also noted that Hurricane 

Hugo created more tern nesting habitat (sandy areas). 

Wunderle and others (1992) found increases in Mangrove Cuckoos four months after 

Hurricane Gilbert, but a limited sample size (n = 0 pre-storm, n = 3 post-storm) and increases in 

detection rates makes this increase doubtful. Overall, Wunderle and others (1992) found that total 

bird abundance increased in mangrove forest four months after Hurricane Gilbert, but this also could 

be a result of increased detection rates for birds after the storm. Mangrove Cuckoos are common in 

Florida and Caribbean coastal mangroves and oak hammocks (e.g., 4.7 Mangrove Cuckoos/km on 

transects in Puerto Rico, Kepler and Kepler, 1978) and would be an ideal species to monitor postCharley at JNDDNWR, especially if pre-storm data exist. The species also has lost 60% of its 

habitat in south Florida to land cleared for residential and agricultural uses (Hughes, 1997). 

Cuckoos forage on lepidopterans, Anolis and orthopterans, which should all increase post-Charley 

based on previous hurricane research (Hughes, 1997, Reagan, 1991, Torres, 1992, Waide, 1991a). 

Mangrove Cuckoos, however, may be absent from forest fragments of <12.8 ha (Bancroft and 

others, 1995). 
Open-File Report 2006-1126 25

Another songbird, the Black-whiskered Vireo, may also be an excellent indicator species of 

mangrove forest habitat conditions at JNDDNWR. This vireo inhabits coastal mangroves and 

hardwood forests in southern Florida, and specializes in mangroves in Florida (Chace and others, 

2002). Black-whiskered Vireos are foliage gleaners of insects or fruit found high in trees (Cruz, 

1980b, 1987), which makes them ideal for assessing recovery of old growth mangrove forests. The 

species is also highly susceptible to parasitism (>50%, Chace and others, 2002) from a recent 

invader, the Shiny Cowbird (Molothrus bonariensis), a species that will probably increase after the 

storm and should also be monitored. 

Some bird populations increase with changes in habitat caused by storms (e.g., species of 

shrubs, grasslands, and wetlands; Wiley and Wunderle, 1993). Arengo and Baldessarre (1999) 

believed that hurricanes may benefit Greater Flamingos (Phoenicopterus ruber) in wetland habitats 

of the Yucatán Peninsula, Mexico, by changing salinity, food quality, density, and availability, i.e., 

water depth. By monitoring species presence and absence from sites, managers could track changes 

in bird communities, bird species extinctions and additions, and turnover rates on the refuge 

(Boulinier and others, 1998, Nichols and Conroy, 1996, Nichols and others, 1998a, 1998b). 

Seagrass beds: manatee habitat 

Research suggests that intact seagrass beds are generally resistant to the physical forces of 

extreme storms (Tilmant and others, 1994, Whitfield and others, 2002). Furthermore storms are 

thought to improve seagrass meadows by removing detritus and necrotic tissue, resulting in healthy 

growth after the storm (Whitfield and others, 2002). Significant localized damage, however, can 

occur from sediment deposition after hurricane-induced erosion, as occurred at the Captiva breach 

and in Mississippi Sound after Hurricane Camille (Eleuterius and Miller, 1976); or from wave action 

on patchy, fragmented beds destabilized by propeller scars, motor vessel groundings, or natural 

blowouts. Past research has shown that scarring can be enlarged and recovery of scars slowed or 
Open-File Report 2006-1126 26

reversed under hurricane forces (Whitfield and others, 2002). The USGS assessment team could not 

evaluate the hurricane’s impact to seagrass in the entire refuge complex. Given the degree of 

propeller scars reported for the region in 1995 (Sargent and others, 1995) and 2004 (Madley 2004), it 

is possible more localized damage occurred in those areas with scarring. The new scars by tree 

drags may have further destabilized the area near the breach making it vulnerable to new storms. 

 The USGS assessment team recommends that refuge staff examine the post-hurricane aerial 

photographs for any large injuries to the seagrass beds within the refuge complex boundaries. If an 

on-site visit to these sites shows major instability, it may warrant management action. Whitfield and 

others (2002) and Kenworthy and others (2002) offer management approaches to stabilize degraded 

areas. Such action should speed recovery and prevent further injury. Continual monitoring for 

vessel groundings and major scarring, with options to remedy such injuries when they occur, should 

be considered for inclusion in the Refuge Management Plan. But as every manager knows, 

prevention is always preferred over remediation. 

With seagrass beds extending beyond refuge boundaries, the group also recommends a 

regional approach to damage assessment and future monitoring and research. The refuge complex 

has an excellent partnership with the Sanibel–Captiva Conservation Foundation and its Marine 

Laboratory. Two studies on seagrass integrity and ecological function are part of their core research 

program (Bortone and others, 2004) and include monitoring within the JNDDNWR Complex. A 

larger regional collaboration with the South Florida Water Management District and the Florida 

Department of Environmental Protection is part of these studies and offers possibilities to develop a 

larger partnership. The refuge, foundation, and its partners may want to consider expanding 

monitoring to sites beyond Sanibel and Captiva islands and into Pine Island and Matlacha Pass 

NWRs, perhaps in conjunction with monitoring on some of the mangrove island bird rookeries. 
Open-File Report 2006-1126 27

Manatee population 

The Florida manatee is listed as endangered under both federal and state law. Concerns 

regarding Hurricane Charley’s impact on manatees focus on three issues: (1) direct mortality, (2) 

permanent emigration of individuals out of the area as a result of the storm, and (3) the loss or 

degradation of seagrass beds, an important food source for manatees. 

Mortality and emigration concerns are based on analysis of extreme storms that struck the 

Florida panhandle and north Gulf Coast in the 1980s and 1990s. Mark-recapture statistical analysis 

of manatee photo-identification data (Langtimm and Beck, 2003) identified lower adult survival 

rates for manatees of the region during three years with storms rated Category 3 or higher on the 

Saffir-Simpson hurricane scale: 1985 with Hurricanes Elena and Kate, 1993 with the March “Storm 

of the Century,” and 1995 with Hurricane Opal. Data suggest that extreme storms have a significant 

effect on adult survival rates; however, the apparent drop in survival also might be explained, at least 

in part, by emigration from the region. 

Loss or degradation of seagrasses can result in lower manatee reproduction rates as well as a 

lower number of individuals that the habitat can support. Seagrass beds degraded by propeller are of 

special concern because they are more vulnerable to hurricane forces (Whitfield and others, 2002) 

and slower to recover than intact seagrass beds (Kenworthy and others, 2002). 

Little is known about what cues manatees use to discern the approach of a major storm or 

what strategies they use to protect themselves. Given the manatee is a tropical species, one would 

expect that they have developed behaviors to deal with tropical storms. Several strategies could be 

employed: move along the coast line away from the storm, rest on the bottom of a deep channel and 

rise only when needed to breathe, and/or hunker down in a protected inlet or cove. The 

effectiveness of these behaviors and the vulnerability of manatees to storm forces should depend on 

(1) the destructiveness of a hurricane, which varies by physical factors such as wind intensity, speed 

and duration of the storm, storm surge, occurrence of battering waves; (2) physical features of the 
Open-File Report 2006-1126 28

coastline that can offer protection (barrier islands, protected coves), and (3) coincidental factors such 

as the density of manatees in the strike area, the number of storms within a season, and occurrence 

with other health or mortality risks. 

 Hurricane Charley produced hurricane force winds throughout the JNDDNWR Complex, 

with the most intense winds crossing North Captiva and northern Pine Island. However, with the 

exception of the area north of the Matlacha Bridge, relatively few high-use manatee areas 

experienced the strongest winds. Although Charley was a Category 4 storm when it hit, its potential 

destruction was reduced by the compact size, short duration, and the lack of a significant storm 

surge. The outer barrier islands of Sanibel, Captiva, and North Captiva and the inner barrier Pine 

and Little Pine Islands should have provided some physical protection along with the deeper 

channels in the pass and sound (Fig. 24). The relatively fast speed of the storm eliminated the 

development of two additional forces that also could be dangerous to manatees – storm surge and 

battering waves. All of these factors suggest that the manatee population in the refuge area did not 

experience a major direct impact from Hurricane Charley. Given the seagrass in the area did not 

sustain heavy damage it is likely the magnitude of impact to the southwest manatee subpopulation 

was minimal. 

Several studies are already underway to monitor and assess the impact to manatees. These 

should not require resources from the refuge. USGS Sirenia Project, FWRI, and Mote Marine 

Laboratory are collaborating under the direction of Dr. Catherine Langtimm to incorporate analysis 

of effects of the 2004 hurricanes into their long-term study to estimate manatee population 

parameters using photo-identification data. Estimates of adult survival will require at least two years 

of data from the winter aggregation sites, but an assessment for impact signatures in the data will be 

completed after the end of one year. Annual monitoring by Mote Marine Laboratory at Matlacha 

Isles and the Ft. Myers Power Plant will continue and should provide information on resightings of 

known individuals and whether a percentage of animals are missing from their usual winter refuge or 
Open-File Report 2006-1126 29

have been documented at another refuge. Mote Marine Laboratory under the direction of Dr. John 

Reynolds continues to conduct aerial surveys in Lee County and will be comparing post-hurricane 

distributions to those from previous years. FWRI continues to monitor manatee carcass recovery, 

and under the direction of Dr. Holly Edwards will again conduct a winter synoptic survey of 

manatees at the aggregation sites in the region. All of these data will be analyzed by researchers at 

their respective institution and reviewed by the Manatee Population Status Working Group under the 

auspices of the Florida Manatee Recovery and Implementation Team as indicators of possible effects 

to the population. USGS will be happy to forward information and reports as they become available, 

put Refuge personnel in touch with key researchers, and provide continued technical support 

regarding manatee issues. 

Other trust species 

The refuge staff has observed eastern indigo snakes at drift fence surveys from 2003-2005 

(K. Pednault-Willet, personal observation. If a population exists on Sanibel Island, we expect that 

little or no mortality occurred because of Hurricane Charley. The opening of forest canopy by the 

storm should provide more suitable habitat and potentially more prey for this threatened snake (J. M. 

Meyers, personal observation from ongoing telemetry study in Georgia). 

Vegetation

We recommend that permanent plots for monitoring vegetation recovery or mortality be 

established in the refuge’s mangrove forests. We believe that monitoring vegetation in a rigorous, 

quantitative manner with appropriate quality assurance and control may benefit wildlife habitat 

management. In this regard, the refuge is fortunate to have a partner in the Sanibel–Captiva 

Conservation Foundation, and its marine laboratory. Professional staff at the lab have established a 

network of 24 vegetation plots in the mangroves of the JNDDNWR Complex, or nearby sites. Three 
Open-File Report 2006-1126 30

plots were established at each of eight locations, with four locations representing impounded 

mangroves and four locations being non-impounded mangrove forest. Data derived from these plots 

are already proving useful. We recommend some improvements for the plots for long-term 

monitoring. At present the plots are not permanent. A center stake is needed and individual stems 

should be tagged, and mapped (Fig. 43). Stem mapping (Fig 44) and the use of permanent, 

individually numbered, aluminum tree tags will greatly reduce the possibility of error during 

subsequent surveys of the plots, allow for measuring growth, recruitment, and delayed mortality 

(Ward and others 2006). Mapping is valuable if another storm occurs; you only need to find a 

single, tagged stem to reconstruct the entire plot based on geometry. Finally, we recommend that 

these plots be established also in waterbird islands and the Shell Mound Trail mangrove forests. 

 Vegetation plots (at least two) should be established on each waterbird island, where 

possible, especially Bird Key, Hemp Island, and Givney Key. An alternate method may be required 

on the smaller fringe and overwash islands. New plots in non-mangrove vegetation, such as the 

tropical hammock at Shell Mound Trail and Legion Curve areas would also be beneficial. Because 

of the more complex nature of the vegetation structure in these areas, particularly higher species 

richness, larger plot sizes will be needed. Once established, the plots need to be sampled annually 

for approximately five years and then they can be split into two groups with each group sampled 

every other year. 

The survey team visited only a small portion of the JNDDNWR Complex, yet we observed a 

variety of invasive exotics. Conducting surveys for this group of plants requires different methods 

than for monitoring recovery. The only effective method is repeated, 100% coverage, followed by 

treatment to eradicate the pest plants. Seedlings of some exotic plants existed in the mangrove 

forests prior to Hurricane Charley, but were suppressed by the intact forest canopy. Loss of the 

mangrove canopy may allow these seedlings to begin vigorous growth. Furthermore, tip-up mounds 

will provide a different type of habitat for both native and exotic plants to colonize. 
Open-File Report 2006-1126 31

 We provide, here, some recommendations for determining sediment elevation in mangrove 

forests in relation to recovery of the forests. In may not seem to be logical, or feasible, but sampling 

sediment elevation is necessary. We know that large scale disturbance can result in sediment 

collapse in mangroves and retard, or even, prevent recovery (Cahoon and others, 2003). We 

recommend a study to look at sediment elevation changes in the heavily damaged mangroves. At 

least two sites should be examined, one on a large waterbird island (Lumpkin, Hemp, Givney) and 

the other in the Shell Mound Trail – Power Line Road area. The idea would be to test potential 

management actions that could be taken to prevent, slow, or ameliorate elevation loss. Such actions 

might include planting mangrove propagules, especially the red mangrove, with and without 

fertilization. An additional factor to examine is wetland water elevation. The experiment would be 

designed to give an answer as to which course of action (above) is feasible for refuge managers. 

Ecosystem function and refuge management

Disturbances, especially large infrequent disturbances (LIDs), affect ecosystem function in 

south Florida and the Caribbean basin. Ecosystems there have developed and are maintained by the 

periodic severe hurricanes (LIDs) on approximately 20-25 year intervals or more. Although 

ecologists have recognized the importance of LIDs in maintaining ecosystems (Turner and Dale, 

1998), there is still much to learn (Tanner and others, 1991). In the Caribbean basin, hurricanes are 

the major LID that organizes natural systems (Walker and others, 1991). 

Major ecosystem structural changes occur with hurricanes. One of the most important 

factors that result from hurricanes is control of species composition (Walker and others, 1991). 

Plant growth and recolonization occurs rapidly after storms, but predicting effects of storms is 

difficult because of the heterogeneity of storm damage within relatively small areas and differences 

between storms (Brokaw and Grear, 1991, Brokaw and Walker 1991, Walker 1991). Hurricanes 

also affect some aspects of ecosystem dynamics, such as processes caused from increased nutrients 
Open-File Report 2006-1126 32

from large amounts of litter fall (Tanner and others, 1991). All of these hurricane effects will take 

place on JNDDNWR Complex to some extent, depending on the location and severity of the storm 

in that area. 

Storm effects on animals, after the initial direct mortality (which is usually low), are highly 

correlated to changes in habitat structure and function. Increase in solar radiation in damaged forests 

stimulates plant growth, depending on the seed bank, which in turn creates habitat and food for 

animals (J. Meyers, personal observations). JNDDNWR Complex will experience these changes, 

which are similar to what has occurred after other storms in the Caribbean basin (Brokaw and Grear, 

1991, Brokaw and Walker, 1991, Doyle and others, 1995, Pimm and others, 1994, Scatena and 

others, 1996, Smith and others, 1994, Tanner and others, 1991, Waide, 1991a, 1991b, Walker, 1991, 

see also Biotropica Special Issue 28[4a]). Most vegetation at JNDDNWR Complex will recover 

rapidly. Exceptions may be old growth mangrove forests, which will recover slowly or not at all 

(see mangrove section). Insects, probably least disturbed by storms of all animal classes, will 

increase in species and numbers (outbreaks, Waide, 1991b). Butterflies (associated with new 

growth, see Torres, 1992), frogs (Woolbright, 1991, 1996), lizards (Reagan, 1991), and freshwater 

shrimp (Covich and others, 1996) increased after Hurricane Hugo. These increases, if they occur on 

JNDDNWR Complex, may affect populations of trust species, such as the threatened indigo snake 

and migratory birds. A modified/improved design and analysis for sampling trust species poststorm, e.g., presence/absence especially for birds, would be beneficial for long-term management 

and may also provide information on hurricane effects for management on other refuges in areas 

affected/unaffected by the hurricanes of 2004 (Boulinier and others, 1998, Nichols and Conroy, 

1996, Nichols and others, 1998a, 1998b). A regional approach using this type of design and analysis 

for all refuges (damaged and undamaged by hurricanes in coastal Florida and Alabama in 2004) may 

provide valuable information on the effects of the storms and potential management strategies for 

many priority, endangered, and trust species. 
Open-File Report 2006-1126 33

RECOMMENDATIONS 

Birds, other trust species, and their habitats 

 (1) Continue to monitor waterbird breeding colonies and extend surveys to additional islands 

to document losses or movement of colonies. Take special note of damaged structure and how 

waterbirds use the structures for nesting. Note nest losses caused by storm overwash in areas where 

tree or shrub nesting waterbirds nested on the ground. Publish recovery results related to storm and 

renesting in state or regional journal. 

 (2) Develop an ecological indicator for monitoring mangrove habitat recovery using the 

Mangrove Cuckoo and Black-whiskered Vireo. Use survey methods that account for detection 

probabilities (distance sampling or double-observer) on transects or point counts. 

 (3) Continue to monitor endangered species (e. g., eastern indigo snake, manatee, and Bald 

Eagle). Publish results of Bald Eagle renesting if it occurs in local or state bird journal. 

 (4) Continue to monitor sea grass beds for damage (losses after storm in previously damaged 

area, e.g., propeller damaged areas) and recovery. 

 (5) Continue cooperative manatee surveys with other agencies and provide information for 

regional approach to potential impact of major storms on manatee survival within three years poststorm. 

 (6) Develop a regional approach to monitoring effects of hurricanes on refuges using a 

species presence-absence method (Nichols and Conroy 1996; Boulinier and others, 1998, Nichols 

and others, 1998a, 1998b) (e.g., presence-absence, would be beneficial for long-term management 

and may also provide information on hurricane effects for management on other refuges in areas 

affected/unaffected during 2004-2005). 

 
Open-File Report 2006-1126 34

Vegetation, Hydrology, and Sediment 

(1) Upgrade the existing network of mangrove vegetation plots by using permanent tree tags, 

adding center stakes and mapping the locations of individual stems. Add plots to waterbird islands 

and the Shell Mound Trail area. 

(2) Establish sediment surface elevation monitoring sites at the Shell Mound Trail and on 

one of the larger waterbird islands to monitor for peat collapse. 

(3) Develop an understanding of what the pre-development watershed was like. What was 

connected where and how did the surface water flow? This is necessary so that managers can 

accurately judge what has changed. Some of this information is, or will soon be, available based on 

historic nautical charts (see Fig. 31). Other parts will need to be developed based on new data (see 

below). 

(4) An accurate topographic map of the JNDDNWR should be developed and entered in to 

the refuges GIS database. The “standard” USGS 7.5 minute Digital Ortho-photo Quarter 

Quadrangles (DOQQ) do not have the necessary vertical detail. A survey using small footprint 

airborne LIDAR (LIght Detection And Ranging) could yield the necessary information. This 

information would be valuable for more than just hydrology, it could aid in vegetation and wildlife 

work. 

(5) All water control structures and culverts on refuge roads should be located, mapped, 

measured for their size and elevation above mean sea level, and checked to see if they are functional. 

The data can be spatially referenced and put in GIS. 

(6) Three permanent stations should be established to monitor surface water level and 

conductivity on the refuge. One station should be placed in each impoundment and one in the bay, 

possibly near the junction of the dike that separates the two. Hypsometric curves need to be 

developed so that stage levels can be converted to flooding frequencies in the wetlands in the 

impoundments. Enough data need to be gathered to enable refuge staff to be certain, that when a 
Open-File Report 2006-1126 35

water control board is set to a given height, they know how much of an impoundment is flooded. 

The impoundments are more than the open water area, they include wetlands also. 

(7) Water levels should also be monitored in the interior freshwater wetlands of the refuge. 

This could be accomplished with staff gauges (and regular visits by staff) or by carefully choosing 

one or two sites for more permanent stations. 

(8) Continue to monitor and eradicate exotic plants, especially in hurricane damaged areas. 

 

Acknowledgements 

We thank Sara McDonald and FWRI for data and graphics on manatee distributions, Judd 

Kenworthy of NOAA’s Center for Coastal Fisheries and Habitat Research and Brad Robbins from 

Mote Marine Laboratory for reprints and information on seagrasses, and Dennis Krohn for 

information on the physical attributes of Hurricane Charley. Comments and suggestions from James 

Wiley, Graham Smith, Don Cahoon and an anonymous reviewer improved the manuscript. We 

especially thank the staff of J. N. “Ding” Darling NWR Complex for excellent assistance in the field 

and for providing Figures 1-5. Funding for this work was provided by the Office of the Eastern 

Regional Director, USGS. 
Open-File Report 2006-1126 36

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Open-File Report 2006-1126 40

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Table 1. Refuge, habitat, and locations for hurricane damage assessment using photographs (canopy 

and terrestrial), bearings, and GPS, 21-24 September 2004, J. N. “Ding” Darling National Wildlife 

Refuge (NWR) Complex, Sanibel, Florida. 

Refuge Habitat Location name 

J. N. “Ding” Darling NWR mangrove MG-05 

J. N. “Ding” Darling NWR mangrove GP 5 

J. N. “Ding” Darling NWR mangrove unknown 

J. N. “Ding” Darling NWR mangrove MG-06 

J. N. “Ding” Darling NWR mangrove Shell Mound 

J. N. “Ding” Darling NWR oak hammock Legion Curve 

J. N. “Ding” Darling NWR mangrove and field Power Line Road 

J. N. “Ding” Darling NWR mangrove MG-07, Dixie-Beach Boulevard 

Matlacha Pass NWR mangrove island Lumpkin Island 

Matlacha Pass NWR mangrove island Upper Bird Island 

Matlacha Pass NWR hammock - scrub Upper Bird Island 

Matlacha Pass NWR mangrove island Givney Key 

Matlacha Pass NWR mangrove island Lower Bird Island 

Pine Island NWR mangrove island Bird Key 

Pine Island NWR mangrove island Bird Key 

Pine Island NWR mangrove island Hemp Island 

________________________________________________________________________ 
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Table 2. General characteristics of seven waterbird islands visited by the survey team, 21-24 

September 2004, “Ding” Darling National Wildlife Refuge Complex. NM = Not measured; Other = 

tropical hardwood species. 

_____________________________________________________________________________ 

________Tree Density (number/ha)_______

Islands Geomorphic 

Type 

Black 

mangrove 

Red 

mangrove 

White 

mangrove

Other Tree Mortality 

Tarpon Bay 

Keys Overwash islands NM NM NM NM 

None apparent 

based on 

visual 

inspection 

Lower Bird 

Island Fringe NM NM NM NM 0 - 10%

Givney Key Fringe and basin 1200 200 0 0 0 - 17%

Upper Bird 

Island 

Fringe and 

overwash 1000-1600 0-200 0-600 0 0 - 25%

Lumpkin 

Island Fringe and basin 600-800 1200-1400 0 0 50 - 71%

Hemp Island Fringe and basin NM NM NM 900 50 - 75%

Bird Key Fringe and basin 400-900 100-200 0 0 60 - 90%
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Table 3. A partial list of plant species observed, or known to occur, on J.N. “Ding” Darling National 

Wildlife Refuge Complex, Florida. Also listed in the exotics category are species that may become 

of concern to management in the future (see Horvitz and others, 1995, 1998). 

Common Name Scientific Name Observed Growth habit 

NATIVES 

Leather fern Acrostichum aureum Yes Fern 

Black mangrove Avicennia germinans Yes Tree 

Red mangrove Rhizophora mangle Yes Tree 

White mangrove Laguncularia racemosa Yes Tree 

Buttonwood Conocarpus erectus Yes Tree 

Gumbo limbo Bursera simaruba Yes Tree 

Jamaica dogwood Piscidia piscipula Yes Tree 

Live oak Querus virginiana Yes Tree 

Sea grape Coccoloba uvifera Yes Tree 

Coral bean Erythrina herbacea Yes Shrub / Tree 

Cabbage palm Sabal palmetto Yes Palm 

Cats claw Pithecellobium unguis-cati Yes Shrub 

Necklace pod Sophora tomentosa Yes Shrub / Tree 

Seaside mahoe Thespesia populnea Yes Shrub / Tree 

Christmas berry Lycium carolinianum Yes Shrub 

Coin vine Dalbergia ecastophyllum No Vine 

Mangrove rubber vine Rhabdadenia biflora Yes Vine 

Nicker bean Caesalpinia spp. Yes Vine 

Milkweed vine Mikania scandens Yes Vine 

Milkwithe Sarcostemma clausem Yes Vine 

Marine vine Cissus trifoliata No Vine 

Virginina creeper Parthenocissus quinqefolia Yes Vine 

Poison ivy Rhus toxicodendron Yes Vine 

Devil's claws Pisonia aculeata Yes Vine 

Grapes Vitis spp. Yes Vine 

Morning glories Ipomoea spp. Yes Vine 

Snowberry Chiococca alba No Vine 

EXOTICS 

Brazillian pepper Schinus terebinthifolius Yes Shrub / Tree 

Papaya Carica papya Yes Tree 

Rosary pea Abrus precatorius Yes Vine 

Air potato Dioscorea bulbifora Yes Vine 

Lather leaf Colubrina asiatica No Vine 

Gold coast jasmine Jasminum dichotomum No Vine 

Brazilian jasmine Jasminum fluminense No Vine 

Mysore raspberry Rubus albescens No Vine 

Pothos Epipremnum pinnatum No Vine 

Caleurpa Cauleurpa taxifolia No Marine alga 
Figure 1. J. N. “Ding Darling National Wildlife Refuge Complex, Charlotte and Lee Counties, 

Florida. 

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Figure 2. Habitat types of J. N. “Ding” Darling National Wildlife Refuge, Florida. 

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Figure 3. Islands surveyed on Matlacha Pass National Wildlife Refuge, Florida, 20-24 September 

2004. 

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Figure 4. Islands surveyed on Pine Island National Wildlife Refuge, Florida, 20-24 September 2004. 

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Figure 5. Locations of study sites for Hurricane Charley damage assessment, J. N. “Ding” Darling 

National Wildlife Refuge, Florida, 20-24 September 2004. 

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Figure 6. Depiction of the surface wind field of Hurricane Charley just prior to landfall near Ding

Darling National Wildlife Refuge. Analysis and graphic provided by NOAA’s Hurricane Research 

Division of the Atlantic Oceanographic and Meteorological Laboratory 

(http://www.aoml.noaa.gov/hrd/Storm_pages/charley2004/wind.html). The eye of the hurricane is 

west of the arrow depicting the forward motion of the storm.

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Figure 7. Aerial photograph of the breach at North Captiva Island. Graphic provided by the USGS 

Coastal & Marine Geology Program, Hurricane and Extreme Storm Impact Studies. Accessed 

November 2004. http://coastal.er.usgs.gov/hurricanes/charley/index.html. 

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Figure 8. Visually estimated open coastal high water levels during Hurricane Charley (based on 

unsurveyed estimates subject to change and corrections) August 24, 2004. Data and Figure provided 

to USGS by the Coastal High Water Study Team under the Federal Emergency Management Agency 

(FEMA). 
Figure 9. Visually estimated open coastal high water levels during Hurricane Charley (based on 

unsurveyed estimates subject to change and corrections) August 24, 2004. Data and Figure provided 

to USGS by the Coastal High Water Study Team under the Federal Emergency Management Agency 

(FEMA). 

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Figure 10. Moderate damage from Hurricane Charley, 13 August 2004, to mangrove habitat along 

Wildlife Drive, “Ding” Darling National Wildlife Refuge, Sanibel, Florida, photographed 21 

September 2004. 

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Figure 11. Severe damage from Hurricane Charley, 13 August 2004, to mangrove habitat on the 

Shell Mound Trail, “Ding” Darling National Wildlife Refuge, Sanibel, Florida, photographed 21 

September 2004. 

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Figure 12. Moderate damage from Hurricane Charley, 13 August 2004, to upland live oak forests 

near “Legion Curve,” “Ding” Darling National Wildlife Refuge, Sanibel, Florida, photographed 22 

September 2004. 

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Figure 13. Seagrass beds at low tide along Wildlife Drive, “Ding” Darling National Wildlife 

Refuge, Sanibel, Florida, photographed 21 September 2004. Twenty to 30 wading birds were 

foraging in the area. 

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Figure 14. Catastrophic damage from Hurricane Charley, 13 August 2004, on the island edge (top) 

and interior (bottom) of Lumpkin Island, Matlacha Pass National Wildlife Refuge, Lee County, 

Florida, photographed 23 September 2004. 

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Figure 15. Moderate damage from Hurricane Charley, 13 August 2004, on Upper Bird Island (top), 

island edge (middle) and interior (bottom), Matlacha Pass National Wildlife Refuge, Lee County, 

Florida, photographed 23 September 2004. 

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Figure 16. Moderate damage from Hurricane Charley, 13 August 2004, on Givney Key: island edge 

(top) and interior (bottom), Matlacha Pass National Wildlife Refuge, Lee County, Florida, 

photographed 23 September 2004. 

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Figure 17. Moderate damage from Hurricane Charley, 13 August 2004, on Lower Bird Island, 

Matlacha Pass National Wildlife Refuge, Lee County, Florida, photographed 23 September 2004. 

Loss of leaf cover occurred on about 50% of coverage. 

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Figure 18. Moderate damage from Hurricane Charley, 13 August 2004, on Lower Bird Island: 

island edge (top – moderate), island edge (middle – mild), and island interior (bottom), Matlacha 

Pass National Wildlife Refuge, Lee County, Florida, photographed 23 September 2004. 

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Figure 19. Catastrophic damage from Hurricane Charley, 13 August 2004, on Bird Key: island edge 

(top, large snapped black mangrove is sprouting) and island interior (bottom), Pine Island National 

Wildlife Refuge, Lee County, Florida, photographed 24 September 2004. 
Figure 20. Catastrophic damage from Hurricane Charley, 13 August 2004, on Hemp Island, Pine 

Island National Wildlife Refuge, Lee County, Florida, photographed 24 September 2004. Large 

numbers of resting waterbirds had been using the island based on white wash and fecal matter on the 

ground. 

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Figure 21. Catastrophic damage from Hurricane Charley, 13 August 2004, on Hemp Island: island 

edge (top), rim (middle) and interior (bottom), Pine Island National Wildlife Refuge, Lee County, 

Florida, photographed 24 September 2004. 

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Figure 22. Wood Storks (3 of 11) leaving Hemp Island, Pine Island National Wildlife Refuge, Lee 

County, Florida, 24 September 2004. 

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Figure 23. Seagrass coverage of Matlacha Pass and Pine Island Sound, Florida, from 1999. Figure 

provided by FWRI. 

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Figure 24. Bathymetry of Matlacha Pass and Pine Island Sound, Florida. Figure provided by FWRI. 
Figure 25. Sand inundation of seagrass bed at the breach on North Captiva Island, Florida, and 

scarring from trees dragged by the storm.

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Figure 26. Relative abundance of manatees within the warm season (Mar.-Nov.) based on aerial 

surveys of Lee County, Florida, conducted 1994-1995 and 1997-1998. Analysis and Figure 

provided by FWRI. 

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Figure 27. Relative abundance of manatees within the cold season (Dec.-Feb.) based on aerial 

surveys of Lee County, Florida, conducted 1994-1995 and 1997-1998. Analysis and Figure 

provided by FWRI. 

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Figure 28. Manatee places and corridors for Matlacha Pass and Pine Island Sound, Florida. 

Analysis and figure provided by FWRI. 

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Figure 29. The Tarpon Bay Keys (red arrows), Florida, as depicted on topographic sheet T-693 from

1859 (left) and in a 1999 false color infra-red aerial photograph. The two images are not to equal 

scales. 

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Figure 30. The old and new of northern Pine Island Sound, Florida. Topographic sheet T-738 from 

1859 (left) and a false color infra-red aerial photograph from 1999. Bird Key is located near the 

center of both images (red arrow). The two images are not to equal scale.

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Figure 31. Comparison of the Shell Mound Trail area and West Impoundment area of J. N. “Ding” 

Darling NWR in 1859 (left) and 1999 (right), Florida. Lack of apparent shoreline change (red 

arrows) and apparent vegetation change (yellow arrows) are indicated. The two images are not to 

equal scale.

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Figure 32. Evidence of human occupation of Hemp Island, Florida. A tip-up mound and pit reveal 

the existence of past Calusa habitation in the form of conch, clam, and whelk shells (upper). The 

presence of lily and papaya plants indicate human occupation much after the Calusa habitation 

(lower). 

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Open-File Report 2006-1126 80

Figure 33. Two views of overwash deposits from Hurricane Charley. The top panel is a close-up 

showing approximately 13 cm of sediment on Upper Bird Island. The bottom panel shows an 

overwash lobe of about 50 cm depth on Givney Island, Florida. 
Figure 34. Levels of hurricane damage range from: leaf burn from salt (upper left), defoliation and 

branch loss (upper right), some stems blown down (lower right), and total canopy loss (lower left). 

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Figure 35. The ability to re-sprout following leaf and branch loss varies greatly among species. In 

general, species with a tropical origin have higher coppicing ability than do temperate species. 

These photographs were taken five weeks following Hurricane Charley. On the left is Black 

mangrove, Gumbo limbo is shown in the center panel, and Sea grape is pictured in the photo on the 

right. The red mangrove, a dominant species in the mangrove forests of Florida, lacks coppicing 

ability. 

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Open-File Report 2006-1126 83

Figure 36. Advanced regeneration, i.e., the presence of seedlings and saplings (from seed banks) in 

a forest’s understory is important to recovery following disturbance. It is abundant in some

locations, such as Bird Key (top), and almost totally absent in other areas, such as Givney Key 

(bottom), Florida. 
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Figure 37. Tip-ups increase sediment micro-topography by creating mounds and pits: Live oak in 

the Legion Curve area (upper left), Black mangrove on Bird Key (lower left), and a Gumbo limbo on 

Hemp Island (center right). 
Figure 38. Tip-up mounds also provide places for species to regenerate and colonize. Here, nonmangrove plant species (yellow arrows) colonize a tip-up mound on Givney Key, Florida. 

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Open-File Report 2006-1126 86

Figure 39. Proliferation of vines is common following disturbance. Nicker bean, a native species, 

grows on Hemp Island (left), while, air potato, and invasive exotic, spreads rapidly along Shell 

Mound Trail, Sanibel Island, Florida (right). 
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Figure 40. Nests of White Ibis (Eudocimus albus) in a Brazilian pepper tree on Hemp Island, 

Florida. 
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Figure 41. A dune swale freshwater marsh (top) and white-topped sedge (Rhyncospora latifolia) 

growing in the marsh (bottom), enlargement), Legion Curve area, Sanibel Island, Florida. 
Figure 42. Water control structures along Powerline Road, Sanibel, Island, Florida. A structure 

(left, yellow arrow) on east side of the road that directs surface water from south to north. A 

partially collapsed culvert (right, yellow arrow) with water flowing from the Shell Mound Trail area 

to east under Powerline Road. 

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Figure 43. Sanibel-Captiva Conservaton Foundation mangrove plot 7 located west of Dixie-Beach 

Boulevard, Sanibel Island, Florida. The yellow arrows point to the pink paint used to mark the 

border of the plot. 

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Open-File Report 2006-1126 91

Figure 44. This figure shows a schematic view of the plot layout (orange circle) used by the USGS 

for mangrove vegetation studies in coastal Everglades, Florida. From the permanent center stake 

(green dot), the distance and bearing (α) from North (N) to each stem is recorded as well as the 

diameter breast height (DBH) and species.