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The mention of commercial product trade names in this report does not constitute endorsement or recommendation for use by the Fish and Wildlife Service, U.S. Department of the Interior. The ecology of regularly flooded salt marshes of
The Okefenokee Swamp is a 200,000 ha palustrine, freshwater wetland in the southeastern United States managed as a National Wildlife Refuge and a National Wilderness Area. Wild- fires frequently occur, modifying vegetation structure and... more
The Okefenokee Swamp is a 200,000 ha palustrine, freshwater wetland in the southeastern United States managed as a National Wildlife Refuge and a National Wilderness Area. Wild- fires frequently occur, modifying vegetation structure and creating the swamp landscape mosaic. Following extensive wildfires in 1954- 1955, the Suwannee River was impounded by a dam (Suwannee River Sill) built outside the Wilderness Area but within the Refuge to exclude fire reoccurrence. By the late 1980s indications were that fire was not being excluded, although the swamp hydrology and vegetation suggested changes due to extended hydroperiod. The dam's effects were delineated with a spatial hydrology model and studies of species' hydrological sensitivities, and an Environmental Assessment considered the multiple uses and management goals to determine the best sill management alternative. The Okefenokee Swamp is a 200,000 ha palustrine, fresh- water wetland in southeast Georgia and northeast Flori...
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The Savannah Harbor is one of the busiest ports on the East Coast of the USA and is located just downstream of the Savannah National Wildlife Refuge (SNWR), which is one of the nation’s largest freshwater tidal marshes. The Lower Savannah... more
The Savannah Harbor is one of the busiest ports on the East Coast of the USA and is located just downstream of the Savannah National Wildlife Refuge (SNWR), which is one of the nation’s largest freshwater tidal marshes. The Lower Savannah River estuary has been studied for years by governmental agencies, water users, universities, and consultants having an interest in controlling water quality and predicting the potential impacts of a proposed harbor deepening. Consequently, many different databases have been created that describe the natural system’s complexity and behaviors. Variables having particular relevance include those describing bathymetry, meteorology, water level, and specific conductance. To evaluate the environmental impacts of the deepening, a three-dimensional hydrodynamic model (3DM) and a “marsh succession model” (MSM) were developed by different scientific teams. The 3DM predicts changes in riverine water levels and salinity in the system in response to potential ...
Invasive exotic species are spreading rapidly throughout the planet. These species can have widespread impacts on biodiversity, yet the ability for native species, particularly long-lived vertebrates, to respond rapidly to invasions... more
Invasive exotic species are spreading rapidly throughout the planet. These species can have widespread impacts on biodiversity, yet the ability for native species, particularly long-lived vertebrates, to respond rapidly to invasions remains mostly unknown. Here we provide evidence of rapid morphological change in the endangered snail kite (Rostrhamus sociabilis) across its North American range with the invasion of a novel prey, the island apple snail (Pomacea maculata), a much larger congener of the kite's native prey. In less than one decade since invasion, snail kite bill size and body mass increased substantially. Larger bills should be better suited to extracting meat from the larger snail shells, and we detected strong selection on increased size through juvenile survival. Using pedigree data, we found evidence of both genetic and environmental influences on trait expression and discovered that additive genetic variation in bill size increased with invasion. However, trends...
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While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate... more
While variation in age structure over time and space has long been considered important for population dynamics and conservation, reliable estimates of such spatio-temporal variation in age structure have been elusive for wild vertebrate populations. This limitation has arisen because of problems of imperfect detection, the potential for temporary emigration impacting assessments of age structure, and limited information on age. However, identifying patterns in age structure is important for making reliable predictions of both short- and long-term dynamics of populations of conservation concern. Using a multistate superpopulation estimator, we estimated region-specific abundance and age structure (the proportion of individuals within each age class) of a highly endangered population of snail kites for two separate regions in Florida over 17 years (1997-2013). We find that in the southern region of the snail kite-a region known to be critical for the long-term persistence of the spec...
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Understanding the spatial scale of population structure is fundamental to long-standing tenets of population biology, landscape ecology and conservation. Nonetheless, identifying such scales has been challenging because a key factor that... more
Understanding the spatial scale of population structure is fundamental to long-standing tenets of population biology, landscape ecology and conservation. Nonetheless, identifying such scales has been challenging because a key factor that influences scaling - movement among patches or local populations - is a multicausal process with substantial phenotypic and temporal variation. We resolve this problem via a novel application of network modularity. When applied to movements, modularity provides a formal description of the functional aggregation of populations and identifies potentially critical scales for ecological and evolutionary dynamics. We first test for modularity using several different types of biologically relevant movements across the entire geographic range of an endangered bird, the snail kite (Rostrhamus sociabilis plumbeus). We then ask whether variation in movement based on (i) age, (ii) sex and (iii) time (annual, seasonal and within-season movements) influences spa...
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Identifying impacts of non-native species on native populations is central to conservation and ecology. While effects of non-native predators on native prey populations have recently received much attention, impacts of introduced prey on... more
Identifying impacts of non-native species on native populations is central to conservation and ecology. While effects of non-native predators on native prey populations have recently received much attention, impacts of introduced prey on native predator populations are less understood. Non-native prey can influence predator behavior and demography through direct and indirect pathways, yet quantitative assessments of the relative impacts of multiple, potentially counteracting, effects on native predator population growth remain scarce. Using ≈20 years of range-wide monitoring data, we tested for effects of a recently introduced, rapidly spreading non-native prey species (Pomacea maculata) on the behavior and demography of the endangered Snail Kite (Rostrhamus sociabilis). Previous studies found that food-handling difficulties caused by the large size of P. maculata (relative to the native P. paludosa) can lead to energetic deficiencies in juvenile kites, suggesting the potential for evolutionary traps to occur. However, high densities of P. maculata populations could facilitate kites by providing supplemental food resources. Contrary to prior hypotheses, we found that juvenile apparent survival increased ≈50% in wetlands invaded by non-native snails. Breeding rates and number of young fledged/successful nests were also positively associated with non-native snail presence, suggesting direct trophic benefits to kites. We found no direct effects of the invasive snail on adult survival or daily nest survival rates. Kite movements and breeding distribution closely tracked the spread of non-native snail populations. Since 2005, kites have been heavily concentrated in northern regions where non-native snails have established. This geographic shift has had hidden costs, as use of northern regions is associated with lower adult survival. Despite negative impacts to this key vital rate, matrix population modeling indicated that the multifarious effects of the non-native snail invasion on kites culminated in increased population growth rates, likely lowering short-term extinction risks. Results suggest that considering only particular components of behavior or demography may be inadequate to infer the population-dynamic importance of non-native prey on native predators, including their role in creating potential evolutionary traps. Our findings provide information pertinent to Everglades restoration, highlighting potential management trade-offs for non-native species that may aid imperiled species recovery yet disrupt other native communities.
Research Interests: Wetlands, Reproduction, Survival Analysis, Environmental Monitoring, Biological Sciences, and 14 moreEnvironmental Sciences, United States, Animals, Florida, Population Density, Snails, Population Growth, Biological evolution, Introduced species, Time Factors, Seasons, Conservation of Natural Resources, Ecological Applications, and Predatory Behavior
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The movements of 165 adult Snail Kites (Rostrhamus sociabilis) were monitored at biweekly intervals in central and southern Florida using radiotelemetry. Over the 3-yr study period (15 April 1992-15 April 1995), 3361 kite locations were... more
The movements of 165 adult Snail Kites (Rostrhamus sociabilis) were monitored at biweekly intervals in central and southern Florida using radiotelemetry. Over the 3-yr study period (15 April 1992-15 April 1995), 3361 kite locations were obtained. Snail Kite habitats were classified as graminoid marsh, cypress prairie, northern lake, miscellaneous peripheral (e.g., agricultural retention ponds), or Lake Okeechobee. Kites showed seasonal
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... Stage data for this site were not available. The flow patterns at Heber Springs have been severely altered by dam. (Note: stage data not available electronically). The dam is holding back flow during the winter and spring months, and... more
... Stage data for this site were not available. The flow patterns at Heber Springs have been severely altered by dam. (Note: stage data not available electronically). The dam is holding back flow during the winter and spring months, and then releasing it during the summer. ...
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Research Interests: Zoology and Waterbirds
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... included for reference. Page 3. QUANTIFYING APPLE SNAIL ABUNDANCE 197 (1 to 3 m tall), emergent sedge which is a dominant feature of the Everglades ecosystem (Loveless 1959, Wood & Tanner 1990). Wet prairie... more
... included for reference. Page 3. QUANTIFYING APPLE SNAIL ABUNDANCE 197 (1 to 3 m tall), emergent sedge which is a dominant feature of the Everglades ecosystem (Loveless 1959, Wood & Tanner 1990). Wet prairie habitats ...
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Historical vegetation data are important to ecological studies, as many structuring processes operate at long time scales, from decades to centuries. Capturing the pattern of variability within a system (enough to declare a significant... more
Historical vegetation data are important to ecological studies, as many structuring processes operate at long time scales, from decades to centuries. Capturing the pattern of variability within a system (enough to declare a significant change from past to present) relies on correct assumptions about the temporal scale of the processes involved. Sufficient long-term data are often lacking, and current techniques have their weaknesses. To address this concern, we constructed multistate and artificial neural network models (ANN) to provide fore- and hindcast vegetation communities considered critical foraging habitat for an endangered bird, the Florida Snail Kite (Rostrhamus sociabilis). Multistate models were not able to hindcast due to our data not satisfying a detailed balance requirement for time reversibility in Markovian dynamics. Multistate models were useful for forecasting and providing environmental variables for the ANN. Results from our ANN hindcast closely mirrored the population collapse of the Snail Kite population using only environmental data to inform the model. The parallel between the two gives us confidence in the hindcasting results and their use in future demographic models.
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Page 1. Spatial and Temporal Changes in Tree Islands of the Arthur R. Marshall Loxahatchee National Wildlife Refuge in Response to Altered Hydrologies Prepared by: Laura A. Brandt University of Florida Everglades Research ...
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This report synthesizes extant literature detailing the ecology of bottomland hardwood swamps in the Southeast. The geographic scope focuses the report to the hardwoods occupying the floodplains of the rivers whose drainages originate in... more
This report synthesizes extant literature detailing the ecology of bottomland hardwood swamps in the Southeast. The geographic scope focuses the report to the hardwoods occupying the floodplains of the rivers whose drainages originate in the Appalachian Mountains/Piedmont and ...
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ABSTRACT Camera traps have increased our knowledge of animal distribution, activity, and behavior, but they are rarely used for small mammal research. This is likely because there are few techniques to that allow for species... more
ABSTRACT Camera traps have increased our knowledge of animal distribution, activity, and behavior, but they are rarely used for small mammal research. This is likely because there are few techniques to that allow for species identification, reduce disturbance of bait from non-target animals (e.g., raccoon [Procyon lotor]), and that can be used in all environments. In this paper we present a small mammal camera-trapping methodology, the Hunt trap, which was designed to 1) work in tidal environments, 2) eliminate capture myopathy, 3) allow for successful identification of small mammal species, and 4) allow for continued trapping after disturbance by non-target species. We tested the Hunt trap in the Lower Suwannee National Wildlife Refuge, Florida, USA, during February 2012 to February 2013. Live traps are still the best option when individuals must be physically captured for marking, radiotagging, demographic studies, or physiological assessments. However, if such data are not required, the Hunt trap design is an excellent technique to monitor species diversity, community composition, habitat selection, and distribution with efficiency and minimal effort. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.