Geology topics

Joshua D. Stafford

Publications and source records attributed to Joshua D. Stafford.

28 records · Page 2Linked to original sources

USGS2015

Evaluation of autonomous recording units for detecting 3 species of secretive marsh birds

Population status and habitat use of yellow rails ( Coturnicops noveboracensis ), Nelson's sparrows ( Ammodramus nelsoni ), and Le Conte's sparrows ( A. leconteii ) are poorly known, so standardized surveys of these species are needed to inform conservation planning and management. A protocol for monitoring secretive marsh birds exists; however, these species regularly call at night and may be missed during early morning surveys. We tested the effectiveness of autonomous recording units (hereafter, recording units) to survey these species by analyzing recorded vocalizations using bioacoustics software. We deployed 22 recording units at 54 sites in northern Minnesota and eastern North Dakota, USA, and conducted traditional broadcast surveys during May–June, 2010 and 2011. We compared detection probabilities between recording units and standard monitoring protocols using robust-design occupancy models. On average, recording units detected 0.59 (SE = 0.11) fewer Le Conte's sparrows, 0.76 (SE = 0.15) fewer Nelson's sparrows, and 1.01 (SE = 0.14) fewer yellow rails per survey than were detected using the standard protocol. Detection probabilities using the standard protocol averaged 0.95 (yellow rail; 95% CI = 0.86–0.98), 0.93 (Le Conte's sparrow; 95% CI = 0.78–0.98), and 0.89 (Nelson's sparrow; 95% CI = 0.56–0.98), but averaged 0.71 (yellow rail; 95% CI = 0.56–0.83), 0.61 (Le Conte's sparrow; 95% CI = 0.42–0.78), and 0.51 (Nelson's sparrow; 95% CI = 0.19–0.82) using recording units. Reduced detection by recording units was likely due to the ability of human listeners to identify birds calling at greater distances. Recording units may be effective for surveying nocturnal secretive marsh birds if investigators correct for differential detectability. Reduced detectability may be outweighed by the increased spatial and temporal coverage feasible with recording units.

Minnesota, North Dakota↗

USGS2015

Is income breeding an appropriate construct for waterfowl?

Breeding birds use a range of nutrient accumulation and allocation strategies to meet the nutritional demands of clutch formation and incubation. On one end of the spectrum, capital breeders use stored nutrients acquired prior to clutch formation and incubation to sustain metabolism during reproduction, while on the opposite end, income breeders derive nutrients solely from exogenous sources on the breeding grounds. Blue-winged Teal ( Anas discors ) are an ideal candidate to test for adoption of an income strategy among migratory waterfowl because of their small body size, temperate breeding range, and timing of reproduction relative to pulses in nutrient availability within breeding habitats. We collected migrating and pre-breeding Blue-winged Teal ( n = 110) during the warmest spring in over a century in the southern edge of the species’ breeding range, which produced ideal conditions to test for adoption of an income breeding strategy among migratory waterfowl. Regression analyses revealed that females accumulated protein and fat reserves early in follicle development and appeared to mobilize at least some reserves coincident with the onset of clutch formation. Accumulation and subsequent mobilization of nutrient reserves was inconsistent with adherence to an income breeding strategy and suggested breeding Blue-winged Teal used capital (albeit locally acquired) for reproduction. Our results add to existing knowledge on the ubiquity of endogenous nutrient reserve accumulation prior to and during reproduction by waterfowl, perhaps suggesting endogenous nutrient reserves are universally used for clutch formation or incubation to some degree. If indeed Blue-winged Teal and other waterfowl universally use capital for breeding, research and conservation efforts should shift from evaluating whether an income breeding strategy is used and focus on when and where necessary capital is acquired prior to clutch formation.

Journal of Ornithology↗

USGS2014

Influence of item distribution pattern and abundance on efficiency of benthic core sampling

ore sampling is a commonly used method to estimate benthic item density, but little information exists about factors influencing the accuracy and time-efficiency of this method. We simulated core sampling in a Geographic Information System framework by generating points (benthic items) and polygons (core samplers) to assess how sample size (number of core samples), core sampler size (cm 2 ), distribution of benthic items, and item density affected the bias and precision of estimates of density, the detection probability of items, and the time-costs. When items were distributed randomly versus clumped, bias decreased and precision increased with increasing sample size and increased slightly with increasing core sampler size. Bias and precision were only affected by benthic item density at very low values (500–1,000 items/m 2 ). Detection probability (the probability of capturing ≥ 1 item in a core sample if it is available for sampling) was substantially greater when items were distributed randomly as opposed to clumped. Taking more small diameter core samples was always more time-efficient than taking fewer large diameter samples. We are unable to present a single, optimal sample size, but provide information for researchers and managers to derive optimal sample sizes dependent on their research goals and environmental conditions.

Wetlands↗

USGS2014

Error propagation in energetic carrying capacity models

Conservation objectives derived from carrying capacity models have been used to inform management of landscapes for wildlife populations. Energetic carrying capacity models are particularly useful in conservation planning for wildlife; these models use estimates of food abundance and energetic requirements of wildlife to target conservation actions. We provide a general method for incorporating a foraging threshold (i.e., density of food at which foraging becomes unprofitable) when estimating food availability with energetic carrying capacity models. We use a hypothetical example to describe how past methods for adjustment of foraging thresholds biased results of energetic carrying capacity models in certain instances. Adjusting foraging thresholds at the patch level of the species of interest provides results consistent with ecological foraging theory. Presentation of two case studies suggest variation in bias which, in certain instances, created large errors in conservation objectives and may have led to inefficient allocation of limited resources. Our results also illustrate how small errors or biases in application of input parameters, when extrapolated to large spatial extents, propagate errors in conservation planning and can have negative implications for target populations.

Journal of Conservation Planning↗

USGS2014

Spring migration of waterfowl in the Northern Hemisphere: a management and conservation perspective

Spring migration is a key part of the annual cycle for waterfowl populations in the northern hemisphere, due to its temporal proximity to the breeding season and because resources may be limited at one or more staging sites. Research based on field observations during spring lags behind other periods of the year, despite the potential for fitness consequences through diminished survival or cross-seasonal effects of conditions experienced during migration. Consequently, conservation strategies for waterfowl on spring migration are often only refined versions of practices used during autumn and winter. Here we discuss the current state of knowledge of habitat requirements for waterfowl at their spring migratory sites and the intrinsic and extrinsic factors that lead to variability in those requirements. The provision of plant foods has become the main conservation strategy during spring because of the birds’ energy requirements at this time, not only to fuel migration but to facilitate early clutch formation on arrival at the breeding grounds. Although energy sources are important to migrants, there is little evidence on the extent to which the availability of carbohydrate-based food is limiting for many migratory waterfowl populations. Such limitation is relatively unlikely among populations that exploit agricultural grain during migration (e.g. arctic-nesting geese), suggesting that conservation strategies for these populations may be misplaced. In general, however, we found few cases in which an ecological understanding of spring-migrating waterfowl was sufficient to indicate true resource limitation during migration, and still fewer cases where conservation efforts ameliorated these limitations. We propose a framework that aims to address knowledge gaps and apply empirical research results to conservation strategies based on documented limitations and associated fitness impacts on migrating waterfowl. Such a strategy would improve allocation of scarce conservation resources during spring migration and greatly improve ecological understanding of migratory waterfowl and their habitats in the northern hemisphere.

Wildfowl↗

USGS2013

Management of wetlands for wildlife

Wetlands are highly productive ecosystems that provide habitat for a diversity of wildlife species and afford various ecosystem services. Managing wetlands effectively requires an understanding of basic ecosystem processes, animal and plant life history strategies, and principles of wildlife management. Management techniques that are used differ depending on target species, coastal versus interior wetlands, and available infrastructure, resources, and management objectives. Ideally, wetlands are managed as a complex, with many successional stages and hydroperiods represented in close proximity. Managing wetland wildlife typically involves manipulating water levels and vegetation in the wetland, and providing an upland buffer. Commonly, levees and water control structures are used to manipulate wetland hydrology in combination with other management techniques (e.g., disking, burning, herbicide application) to create desired plant and wildlife responses. In the United States, several conservation programs are available to assist landowners in developing wetland management infrastructure on their property. Managing wetlands to increase habitat quality for wildlife is critical, considering this ecosystem is one of the most imperiled in the world.

Book chapter↗

USGS2012

Impacts of mute swans ( Cygnus olor ) on submerged aquatic vegetation in Illinois River Valley backwaters

Wetland loss in North America has been considerable and well documented, and the establishment of exotic species in remaining wetlands can further reduce their ability to support native flora and fauna. In the Chesapeake Bay and Great Lakes ecosystems, exotic mute swans ( Cygnus olor ) have been found to negatively impact wetlands through degradation of submerged aquatic vegetation (SAV) communities. Mute swan populations have expanded into many areas of mid-continental North America outside the Great Lakes ecosystem, but the environmental impact of these populations is not well known. Mid-continental wetlands in North America differ in physical characteristics (e.g., size, depth, and permanency) and aquatic vegetation species composition compared to wetlands in other areas where mute swans have been studied and, thus, may be more or less susceptible to degradation from swan herbivory. To investigate the impact of mute swan herbivory on SAV communities in mid-continent wetlands, we used exclosures to prevent swans from foraging in 2 wetland complexes in central Illinois. Above-ground biomass of vegetation did not differ between exclosures and controls; however, mean below-ground biomass was greater in exclosures (52.0 g/m 2 , SE = 6.0) than in controls (34.4 g/m 2 SE = 4.0). Thus, although swan densities were lower in our study region compared to that of previous studies, we observed potentially detrimental impacts of swan herbivory on below-ground biomass of SAV. Our results indicate that both above-ground and below-ground impacts of herbivory should be monitored, and below-ground biomass may be most sensitive to swan foraging.

Illinois↗

USGS2010

Factors associated with hunter success for ducks on state-owned lands in Illinois, USA

Factors that influence hunter success for waterfowl are subject to varying levels of control by managers. The relative influence of these factors is poorly understood, but such information may be valuable to guide management actions intended to promote successful hunting and communicate management decisions to constituents. We used bag-check data to investigate factors influencing hunter success for mallards Anas platyrhynchos and other dabbling ducks (tribe Anatini) during the period 1981-2000 and 2002 at Illinois public waterfowl areas. Competing models of hunter success for mallards and other dabbling ducks included a negative association with average low temperature during the duck season (uncontrollable by managers) and positive associations with estimates of local and continental duck abundance, factors which we considered partially controllable by managers. Although a certain proportion of variation in hunter success for ducks cannot be directly influenced by managers, we suggest that programs and management efforts, which promote larger continental duck populations (e.g. Conservation Reserve Program) and local duck abundance (e.g. provide quality wetland foraging habitats), may positively influence hunter success.

Illinois↗

USGS2005

Multi-stage sampling for large scale natural resources surveys: A case study of rice and waterfowl

Large-scale sample surveys to estimate abundance and distribution of organisms and their habitats are increasingly important in ecological studies. Multi-stage sampling (MSS) is especially suited to large-scale surveys because of the natural clustering of resources. To illustrate an application, we: (1) designed a stratified MSS to estimate late autumn abundance (kg/ha) of rice seeds in harvested fields as food for waterfowl wintering in the Mississippi Alluvial Valley (MAV); (2) investigated options for improving the MSS design; and (3) compared statistical and cost efficiency of MSS to simulated simple random sampling (SRS). During 2000–2002, we sampled 25–35 landowners per year, 1 or 2 fields per landowner per year, and measured seed mass in 10 soil cores collected within each field. Analysis of variance components and costs for each stage of the survey design indicated that collecting 10 soil cores per field was near the optimum of 11–15, whereas sampling >1 field per landowner provided few benefits because data from fields within landowners were highly correlated. Coefficients of variation (CV) of annual estimates of rice abundance ranged from 0.23 to 0.31 and were limited by variation among landowners and the number of landowners sampled. Design effects representing the statistical efficiency of MSS relative to SRS ranged from 3.2 to 9.0, and simulations indicated SRS would cost, on average, 1.4 times more than MSS because clustering of sample units in MSS decreased travel costs. We recommend MSS as a potential sampling strategy for large-scale natural resource surveys and specifically for future surveys of the availability of rice as food for waterfowl in the MAV and similar areas.

Arkansas, Kentucky, Louisiana, Mississippi, Missou↗

USGS2003

SAS procedures for designing and analyzing sample surveys

Complex surveys often are necessary to estimate occurrence (or distribution), density, and abundance of plants and animals for purposes of re-search and conservation. Most scientists are familiar with simple random sampling, where sample units are selected from a population of interest (sampling frame) with equal probability. However, the goal of ecological surveys often is to make inferences about populations over large or complex spatial areas where organisms are not homogeneously distributed or sampling frames are in-convenient or impossible to construct. Candidate sampling strategies for such complex surveys include stratified,multistage, and adaptive sampling (Thompson 1992, Buckland 1994).

Bulletin of the Ecological Society of America↗