Producing ducks using wire and electricity
Abstract has not been submitted
SEARCH · Search USGS
Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Abstract has not been submitted
In coastal South Carolina, many wetlands are impounded and managed as migratory waterfowl habitat. Impoundment effects on fish production and habitat quality largely are unknown. We used the size-frequency method to estimate summer production of fish guilds in three impoundments along the Combahee River, South Carolina. We predicted that guild-specific production would vary with impoundment salinity, which ranged from 3 to 21 practical salinity units. We expected that marine species that use the estuary as nursery habitat would have greatest production in the impoundment with the highest salinity regime, and that species that inhabit the upper reaches of the estuary would have greatest production in the impoundment with the lowest salinity regime. Finally, we expected that estuarine species would be highly productive in all study impoundments, because these species can reproduce within these structures. We found that guild-specific productivity varied both among years and among impoundments, generally following salinity gradients, though to a lesser extent than expected. Our guild-specific estimates of fish productivity fell on the low end of the range of previously published estuarine fish production estimates. Additionally, we observed large mortality events in the study impoundments each summer. The results of our study indicate that during the summer, the study impoundments provided poor-quality fish habitat to all guilds.
While many migrating and wintering shorebird (Charadriiformes) species face declines in quality and quantity of natural stopover sites, diked wetlands managed for shorebirds may provide supplemental habitat. We describe an integrative shorebird-waterfowl management strategy used at Tom Yawkey Wildlife Center on South Island, South Carolina, during 3 winter-spring seasons (1991-93). We compared shorebird use and invertebrate density between diked, managed wetlands and adjacent natural coastal mudflat areas. About 3,000 shorebirds overwintered each year at the site. Migration numbers peaked at 15,000-19,000 during late May. In 1991, shorebird density and absolute numbers were higher ( P < 0.05) in managed wetlands at high tide than natural mudflats at low tide. In 1993, we counted shorebird density at low tide both in managed wetlands and Mother Norton Shoals, the largest natural area. During February, shorebird frequency was higher in Mother Norton Shoals and lower in managed wetlands than expected values based on area ( P < 0.005). In contrast, from March to May, shorebird frequency was higher in managed wetlands and lower in natural mudflats than expected ( P < 0.005 for each month). Invertebrate density from March to May was generally greater in managed wetlands than at Mother Norton Shoals, which may explain shorebird preference during that time. Greater invertebrate density did not explain the pattern in February. Mean water depth in managed wetlands for each shorebird species was <5 cm except for American avocet ( Recurvirostra americana ) which used deeper water ( x̄ = 8.4 cm, SD = 4.5). Results indicate that an integrative shorebird-waterfowl management strategy provides supplemental shorebird habitat at high tide, and managed wetlands can be preferred to local natural mudflat areas at low tide.
In coastal South Carolina, most impounded marshes are managed for waterfowl; fewer are managed for fishes. Tidal control is central to each strategy but raises concerns that nursery function could be impaired. This research examined the assemblage composition of fishes during early-life stages. We sampled two impoundments of each management type monthly in 2008 and 2009. We used light traps to collect 61,527 sub-adult fish representing 21 species and 16 families and push nets to collect 12,670 sub-adult fish representing 13 species and 11 families. The effective number of species detected at larval stage in “fish” impoundments (summer mean = 2.52 ± 0.20, winter mean = 2.02 ± 0.66) was greater than in “waterfowl” impoundments (summer mean = 1.27 ± 0.14, winter mean = 1.06 ± 0.09); CI = 90 %. Species richness did not differ between management types, but hierarchical linear models predicted differences in assemblage composition. These findings underscore the importance of frequent water exchange for maintaining diverse assemblages of early-life-stage fishes in marsh impoundments.
Avian biology and collection of baseline population data was a major part of the first decade (1951-1961) of field research at the Savannah River Site (SRS). Baseline inventories involving organisms and land-use types were part of the mission in the early contracts between the Atomic Energy Commission (now the Department of Energy) and the University of Georgia prior to the establishment of the Savannah River Ecology Laboratory (SREL) as a National Environmental Research Park Laboratory. About 27% of the SREL publications during this first decade dealt with birds. Since that time, research on the SRS landscape has expanded and broadened with less than 10% of the publications dealing with birds. SRS changed also from an agriculturally dominated area with ca. 40% open areas (fields, crops, pastures) to a timber-managed area with ca. 80% forests, 12% open areas, and 2% open water impoundments. Baseline breeding bird populations of the SRS in the 1950s were typical for the region with avian species richness and density increasing with the age and succession of the vegetation (0-26 species and densities of 0-741 pairs/km2 for the habitats surveyed). During the first decade at the SRS, the resident game bird population of Northern Bobwhites (Colinus virginianus) increased and the Mourning Dove (Zenaida rnacroura) population, a migratory upland game bird, remained stable. Current avian research efforts, as well as new opportunities to reexamine the breeding bird populations and the landscape of SRS, will provide a better understanding of the potential causes of declines of neotropical migratory birds, declines of resident and migratory game birds, and how habitat influences invasions and extinctions of breeding birds in the region. Emphasis for future research and monitoring should be on neotropical migratory bird populations in decline (Yellow-billed Cuckoo, Coccyzus americanus; Eastern Wood-Pewee, Contopus virens; Wood Thrush, Hylocichla mustelina; Prairie Warbler, Dendroica discolor; and Painted Bunting, Passerina ciris), resident species in decline (e.g., Loggerhead Shrike, Lanius ludovicianus), certain species groups (e.g., waterfowl and wading birds), important habitat, and recent invasions and extinctions of breeding species. Old growth forested wetlands should be monitored because of the large number of neotropical migratory birds that depend on this habitat in the southeastern United States. A variety of survey techniques will be needed to determine population trends: line transects, call or song playbacks, roadside point surveys (call counts for game birds), aerial surveys, and presence or absence of species within stratified areas of SRS. The SRS provides opportunity for avian research at the landscape level with the potential to solve problems important to the survival of many bird populations as well as to increase our knowledge on how to manage and conserve our avian natural resources for the future.