Buler J.J.,University of Delaware |
Randall L.A.,National Wetlands Research Center |
Fleskes J.P.,Western Ecological Research Center |
Barrow W.C.,National Wetlands Research Center |
And 3 more authors.
PLoS ONE | Year: 2012
The current network of weather surveillance radars within the United States readily detects flying birds and has proven to be a useful remote-sensing tool for ornithological study. Radar reflectivity measures serve as an index to bird density and have been used to quantitatively map landbird distributions during migratory stopover by sampling birds aloft at the onset of nocturnal migratory flights. Our objective was to further develop and validate a similar approach for mapping wintering waterfowl distributions using weather surveillance radar observations at the onset of evening flights. We evaluated data from the Sacramento, CA radar (KDAX) during winters 1998-1999 and 1999-2000. We determined an optimal sampling time by evaluating the accuracy and precision of radar observations at different times during the onset of evening flight relative to observed diurnal distributions of radio-marked birds on the ground. The mean time of evening flight initiation occurred 23 min after sunset with the strongest correlations between reflectivity and waterfowl density on the ground occurring almost immediately after flight initiation. Radar measures became more spatially homogeneous as evening flight progressed because birds dispersed from their departure locations. Radars effectively detected birds to a mean maximum range of 83 km during the first 20 min of evening flight. Using a sun elevation angle of -5° (28 min after sunset) as our optimal sampling time, we validated our approach using KDAX data and additional data from the Beale Air Force Base, CA (KBBX) radar during winter 1998-1999. Bias-adjusted radar reflectivity of waterfowl aloft was positively related to the observed diurnal density of radio-marked waterfowl locations on the ground. Thus, weather radars provide accurate measures of relative wintering waterfowl density that can be used to comprehensively map their distributions over large spatial extents.
Howard R.J.,U.S. Geological Survey |
Wells C.J.,U.S. Geological Survey |
Michot T.C.,U.S. Geological Survey |
Michot T.C.,University of Louisiana at Lafayette |
Johnson D.J.,National Wetlands Research Center
Environmental Management | Year: 2014
Anthropogenic disturbances in wetland ecosystems can alter the composition and structure of plant assemblages and affect system functions. Extensive oil and gas extraction has occurred in wetland habitats along the northern Gulf of Mexico coast since the early 1900s. Activities involved with three-dimensional (3D) seismic exploration for these resources cause various disturbances to vegetation and soils. We documented the impact of a 3D seismic survey in coastal marshes in Louisiana, USA, along transects established before exploration began. Two semi-impounded marshes dominated by Spartina patens were in the area surveyed. Vegetation, soil, and water physicochemical data were collected before the survey, about 6 weeks following its completion, and every 3 months thereafter for 2 years. Soil cores for seed bank emergence experiments were also collected. Maximum vegetation height at impact sites was reduced in both marshes 6 weeks following the survey. In one marsh, total vegetation cover was also reduced, and dead vegetation cover increased, at impact sites 6 weeks after the survey. These effects, however, did not persist 3 months later. No effects on soil or water properties were identified. The total number of seeds that germinated during greenhouse studies increased at impact sites 5 months following the survey in both marshes. Although some seed bank effects persisted 1 year, these effects were not reflected in standing vegetation. The marshes studied were therefore resilient to the impacts resulting from 3D seismic exploration because vegetation responses were short term in that they could not be identified a few months following survey completion. © 2014 Springer Science+Business Media.
PubMed | The Institute for Marine Research and Observation, University of Queensland, Macquarie University, University of Wollongong and 4 more.
Type: Journal Article | Journal: Nature | Year: 2015
Sea-level rise can threaten the long-term sustainability of coastal communities and valuable ecosystems such as coral reefs, salt marshes and mangroves. Mangrove forests have the capacity to keep pace with sea-level rise and to avoid inundation through vertical accretion of sediments, which allows them to maintain wetland soil elevations suitable for plant growth. The Indo-Pacific region holds most of the worlds mangrove forests, but sediment delivery in this region is declining, owing to anthropogenic activities such as damming of rivers. This decline is of particular concern because the Indo-Pacific region is expected to have variable, but high, rates of future sea-level rise. Here we analyse recent trends in mangrove surface elevation changes across the Indo-Pacific region using data from a network of surface elevation table instruments. We find that sediment availability can enable mangrove forests to maintain rates of soil-surface elevation gain that match or exceed that of sea-level rise, but for 69 per cent of our study sites the current rate of sea-level rise exceeded the soil surface elevation gain. We also present a model based on our field data, which suggests that mangrove forests at sites with low tidal range and low sediment supply could be submerged as early as 2070.
Sheppard J.L.,University of Saskatchewan |
Clark R.G.,University of Saskatchewan |
Clark R.G.,Environment Canada |
Devries J.H.,Institute for Wetland and Waterfowl Research |
And 2 more authors.
Behavioural Processes | Year: 2013
In accordance with the differential allocation hypothesis, females are expected to increase their reproductive investment when mated to high-quality males. In waterfowl, reproductive, investment increased when captive female mallards (Anas platyrhynchos) were mated to more attractive males, but information for wild ducks is lacking. Studies of waterfowl mating systems have focused primarily on the importance of plumage coloration of males and female mate choice, whereas investigations of reproductive ecology examine female attributes and virtually ignore the role of males in investment decisions. Here, we used unique data for 253 pairs of wild mallards to test whether females mated to high-quality males would increase reproductive effort and reproduce more successfully. We derived measurements of female and male body size and condition, and indices of male plumage quality, and related these traits to patterns of reproductive effort and performance of females. Consistent with predictions, yearling females nested earlier and had higher nest survival when mated to males with better plumage scores. Furthermore, when paired with larger bodied males, yearling females renested more often, and nest and brood survival increased among older females. Although the strength of male effects varied with breeding stage and female age or experience, this is one of a few studies to demonstrate an additive effect of male quality on investment and success of females, in free-ranging birds. © 2013 Elsevier B.V.
Middleton B.A.,U.S. Geological Survey |
Johnson D.,National Wetlands Research Center |
Roberts B.J.,Louisiana Universities Marine Consortium
Ecohydrology | Year: 2015
As coastal wetlands subside worldwide, there is an urgency to understand the hydrologic drivers and dynamics of plant production and peat accretion. One incidental test of the effects of high rates of discharge on forested wetland production occurred in response to the 2010 Deepwater Horizon incident, in which all diversions in Louisiana were operated at or near their maximum discharge level for an extended period to keep offshore oil from threatened coastal wetlands. Davis Pond Diversion was operated at six times the normal discharge levels for almost 4months, so that Taxodium distichum swamps downstream of the diversion experienced greater inundation and lower salinity. After this remediation event in 2010, above-ground litter production increased by 2.7 times of production levels in 2007-2011. Biomass of the leaf and reproductive tissues of several species increased; wood litter was minimal and did not change during this period. Root production decreased in 2010 but subsequently returned to pre-remediation values in 2011. Both litter and root production remained high in the second growing season after hydrologic remediation. Annual tree growth (circumference increment) was not significantly altered by the remediation. The potential of freshwater pulses for regulating tidal swamp production is further supported by observations of higher T.distichum growth in lower salinity and/or pulsed environments across the U.S. Gulf Coast. Usage of freshwater pulses to manage altered estuaries deserves further consideration, particularly because the timing and duration of such pulses could influence both primary production and peat accretion. © 2015 The Authors. Ecohydrology published by John Wiley & Sons Ltd.
Ewing R.,University of Utah |
Hamidi S.,University of Texas at Arlington |
Grace J.B.,National Wetlands Research Center
Environment and Planning B: Planning and Design | Year: 2016
There is a long-running debate in the planning literature about the effects of the built environment on travel behavior and the degree to which apparent effects are due to the tendency of households to self-select into neighborhoods that reinforce their travel preferences. Those who want to walk will choose walkable neighborhoods, and those who want to use transit will choose transit-served neighborhoods. These households might have walked or used transit more than their neighbors wherever they lived. Most previous studies have shown that individual attitudes attenuate the relationship between the residential environment and travel choices, and so the effect of the built environment on travel may be overestimated. But there are other researchers who argue the reverse, claiming that residential preferences reinforce built environmental influences. This study assesses the relative importance of the built environment and residential preferences/travel attitudes for a sample of 962 households in the Greater Salt Lake region using structural equation modeling. For the sake of simplicity, we extracted two factors using principal component analysis, one representing the built environment and the other representing residential preferences/attitudes. Our findings are consistent with the view that the neighborhood built environment and residential preferences both influence household’s travel, that the built environment is the stronger influence, and that the built environment affects travel through two causal pathways, one direct and the other indirect, through attitudes. © 2015, © The Author(s) 2015.
Erxleben D.R.,Texas Tech University |
Erxleben D.R.,Texas Parks and Wildlife Department |
Butler M.J.,Texas Tech University |
Ballard W.B.,Texas Tech University |
And 10 more authors.
European Journal of Wildlife Research | Year: 2011
Road-based distance sampling is a common technique used to estimate the density of many wildlife species but potential biases exist unless the target population is randomly distributed around roads. Our objective was to determine if and when Rio Grande wild turkeys (Meleagris gallopavo intermedia; RGWT) were randomly distributed around roads to identify time periods in which road-based surveys would be most appropriate. We used triangulated locations obtained from radiotelemetry of RGWTs in the Edwards Plateau (2001-2003), Rolling Plains (2000-2006), and South Texas (2003-2006) ecoregions. Using a geographic information system, we conducted a use and availability analysis by sex, season, and time of day for each ecoregion to determine RGWT use of areas near roads (<200 m). We found the most appropriate time to conduct road-based distance sampling was from 1 December to 15 March during morning or afternoon. Our results suggested road-based surveys conducted during these periods should yield generally unbiased results in the Rolling Plains and Edwards Plateau ecoregions. We recommend researchers and managers investigate animal distributions around roads before implementing road-based monitoring programs for other wildlife species. © 2010 Springer-Verlag.
Erxleben D.R.,Texas Tech University |
Erxleben D.R.,Texas Parks and Wildlife Department |
Butler M.J.,Texas Tech University |
Ballard W.B.,Texas Tech University |
And 4 more authors.
Journal of Wildlife Management | Year: 2010
Traditional index-based techniques have indicated declines in Rio Grande wild turkey (Meleagris gallopavo intermedia; hereafter, wild turkey) populations across much of Texas, USA. However, population indices can be unreliable. Research has indicated that road-based surveys may be an efficacious technique for monitoring wild turkey populations on an ecoregion level. Therefore, our goal was to evaluate applicability of road-based distance sampling in the Cross Timbers, Edwards Plateau, Rolling Plains, and South Texas ecoregions of Texas. We conducted road-based surveys in each ecoregion during December 2007March 2008 to estimate wild turkey flock encounter rates and to determine survey effort (i.e., km of roads) required to obtain adequate sample sizes for distance sampling in each ecoregion. With simulations using inflatable turkey decoys, we also evaluated effects of distance to a flock, flock size, and vegetative cover on turkey flock detectability. Encounter rates of wild turkey flocks from road-based surveys varied from 0.1 (95 CI= 0.00.6) to 2.2 (95 CI= 0.86.0) flocks/100 km surveyed. Encounter rates from surveys restricted to riparian communities (i.e., areas ≤1 km from a river or stream) varied from 0.2 (95 CI= 0.10.6) to 2.9 (95 CI= 1.56.7) flocks/100 km surveyed. Flock detection probabilities from field simulations ranged from 22.5 (95 CI= 16.329.8) to 25.0 (95 CI= 13.639.6). Flock detection probabilities were lower than expected in all 4 ecoregions, which resulted in low encounter rates. Estimated survey effort required to obtain adequate sample sizes for distance sampling ranged from 2,765 km (95 CI= 2,5972,956 km) in the Edwards Plateau to 37,153 km (95 CI= 12,861107,329 km) in South Texas. When we restricted road-based surveys to riparian communities, estimated survey effort ranged from 2,222 km (95 CI= 2,0922,370 km) in the Edwards Plateau to 22,222 km (95 CI= 19,78225,349 km) in South Texas. © 2010 The Wildlife Society.
Huner J.,Louisiana Ecrevisse |
Jeske C.,National Wetlands Research Center
Freshwater Crayfish | Year: 2010
Waterbirds have vexed Louisiana crayfish farmers since the industry's earliest days. Large flocks are regularly encountered. High densities of crayfish predators and competitors would appear to be detrimental to production. As yet, no definitive studies have determined whether or not "perceived" problems are "real". However, "perceived" problems cause concern among crayfish farmers and should be of concern to those charged with addressing wildlife damage complaints. Conflicts between farmers and conservationists are exacerbated because of the clear value of the Louisiana's 67,000 ha of crayfish impoundments to over 100 species of waterbirds. Concern about waterbirds involves several issues. Direct prédation on crayfish is a clear concern. Birds are also competitors for crayfish food resources, including invertebrates, small vertebrate animals, and un-harvested seeds. Birds impact harvesting by removing cut fish bait and/or crayfish from traps, as well as dislodging traps permitting crayfish to escape. Finally, some birds hasten destruction of emergent vegetation that provides crayfish with protective cover, reduces absolute density per unit area and affords access to the surface during periods of low dissolved oxygen. Specific bird groups include: grebes, pelicans, cormorants, egrets, herons, night-herons, ibises, spoonbills, storks, geese, dabbling ducks, diving ducks, coots, shorebirds, gulls and terns. Information about control methods for dispersing birds, including non-lethal harassment, ex-closures, management of water depth and vegetative cover, and crayfish trap modification will be presented. The seasonality of "problem" birds varies and will be discussed. © 2010 International Association of Astacology.