Geology topics

Sarah J. Thompson

Publications and source records attributed to Sarah J. Thompson.

9 recordsLinked to original sources

USGS2023

Examining dynamic occupancy of gray wolves in Idaho after a decade of managed harvest

Gray wolves ( Canis lupus ) were reintroduced to Idaho, USA, in 1995–1996. The removal of Endangered Species Act protections in 2011 transferred wolf management to the state where wolves were subsequently classified as a harvested (i.e., hunted, trapped) big game species. We implemented a camera-based survey across Idaho from 2016–2021 as part of a population monitoring program. We used the resulting camera images in multi-year, dynamic and single-season occupancy models to examine potential changes in the asymptotic proportion of area occupied by wolves and assess the effect of cumulative wolf harvest from 2016–2021 on occupancy in the last year of the study, 2021. We also wanted to understand how habitat, prey, humans, harvest, livestock, and prey-related wolf removals affected wolf occupancy through their effects on colonization and extinction of occupancy cells through time. Statewide wolf occupancy did not change appreciably over the course of our study, with the proportion of survey cells occupied at an estimated high of 0.44 ± 0.03 (SE) in 2018 and a low of 0.39 ± 0.03 in 2020. Wolf colonization (i.e., probability that a cell switched from unoccupied to occupied between years) was positively associated with forest cover, images of humans, and the percent of neighboring cells that were occupied. Cell extinction (i.e., probability of switching from occupied to unoccupied between years) was negatively associated with neighboring cell occupancy. There were non-linear relationships between wolf harvest, colonization, and extinction. The single-season occupancy model demonstrated a positive relationship between harvest and occupancy at low to moderate levels of harvest (10–30%), but there was also evidence that high levels of harvest (>30%) reduce occupancy. Our results indicate that although harvest might influence wolf occupancy at local scales, wolf occupancy remained relatively constant across the state and wolves remained well distributed across Idaho during the study.

Idaho↗

USGS2022

Optimizing surveys of fall-staging geese using aerial imagery and automated counting

Ocular aerial surveys allow efficient coverage of large areas and can be used to monitor abundance and distribution of wild populations. However, uncertainty around resulting population estimates can be large due to difficulty in visually identifying and counting animals from aircraft, as well as logistical challenges in estimating detection probabilities. Photographic aerial surveys can mitigate these challenges and can allow flight at higher altitudes to minimize disturbance of birds and improve safety for surveyors. We evaluated a photographic aerial survey that incorporated a systematic sampling design with automated photo capture and processing for fall-staging geese at Izembek Lagoon, Alaska, in 2017–2019. Ocular aerial surveys have been completed at Izembek Lagoon for >40 years. For the new photo survey, we used a commercial system to automatically trigger cameras at preset points. We then applied a machine-learning algorithm trained to automatically identify and count geese in our photos, manually corrected those counts, and quantified the algorithm's accuracy. We translated corrected counts into density and extrapolated mean density across the entire lagoon to estimate total population size for Pacific brant ( Branta bernicla ) and cackling geese ( B. hutchinsii ). The automated algorithm undercounted geese, but successfully identified the small subset of photos containing geese. Manual correction was therefore needed only for photos automatically identified as containing geese, allowing substantial reduction of workload. Manually-corrected, photo-based estimates of Pacific brant and cackling goose population sizes were larger and more precise than ocular estimates in all 3 years. To reduce costs with little penalty for variance around population estimates, the photographic survey design could be optimized by reducing the number of transects to ~67% of the current number while still manually correcting all photos in which the automated algorithm detected geese. Further years of both ocular and photo surveys would be needed to calibrate the photo estimates against the >40-year timeseries of the ocular survey, after which the photo series could successfully guide management of Pacific brant. As technologies continue to advance, we expect photographic surveys with automated counting to be easily implemented and advantageous to many monitoring programs.

Alaska↗

USGS2022

Prioritizing habitats based on abundance and distribution of molting waterfowl in the Teshekpuk Lake Special Area of the National Petroleum Reserve, Alaska

Alaska↗

USGS2020

Prioritizing habitats based on abundance and distribution of molting waterfowl in the Teshekpuk Lake Special Area of the National Petroleum Reserve, Alaska

The National Petroleum Reserve in Alaska (NPR-A) encompasses more than 9.5 million hectares of federally managed land on the Arctic Coastal Plain of northern Alaska, where it supports a diversity of wildlife, including millions of migratory birds. Within the NPR-A, Teshekpuk Lake and the surrounding area provide important habitat for migratory birds, including large numbers of waterfowl and shorebirds that use the area for breeding and molting. This area has been designated by the Bureau of Land Management as the Teshekpuk Lake Special Area (TLSA) and is estimated to host 22 percent of the entire Pacific black brant ( Branta bernicla nigricans ) population as it undergoes flightless wing molt. Additionally, numerous other waterfowl species use the area for breeding and molting, including greater white-fronted geese ( Anser albifrons ), snow geese ( Chen caerulescens ), Canada geese ( Branta hutchinsii ), and tundra swans ( Cygnus columbianus ). A data-derived procedure was developed to define important habitats based on recent distributions of molting birds. That procedure was used to identify areas that could be prioritized for exclusion from oil and gas development within a pre-defined “Goose Molting Area” in the TLSA. This analysis was requested by the Bureau of Land Management to provide information for the development of alternative scenarios for an updated NPR-A, Integrated Activity Plan/Environmental Impact Statement. Habitat selections were based on the population densities of Pacific black brant and Canada geese and pre-defined thresholds for the minimum fraction of the population contained within selected areas. Selections were based on long-term records of population density combined with global-positioning system data to reveal small-scale patterns of habitat use. The highest population density of the Pacific black brant was found along the Beaufort Sea coast on the eastern edge of the study area, whereas Canada geese were somewhat more widely distributed. Depending on the selection criteria and width of protective buffers placed around selected habitat units, 52–85 percent of the Goose Molting Area was identified as high-priority habitat. The effectiveness of this approach to habitat protection assumes that buffers around selected habitat units are wide enough to provide adequate protection from disturbance related to oil and gas development. This assumption remained a key source of uncertainty that could be addressed through additional study of disturbance effects on molting waterfowl.

Alaska↗

USGS2017

Vectors, hosts, and control measures for Zika virus in the Americas

We examine Zika virus (ZIKV) from an ecological perspective and with a focus on the Americas. We assess (1) the role of wildlife in ZIKV disease ecology, (2) how mosquito behavior and biology influence disease dynamics, and (3) how nontarget species and ecosystems may be impacted by vector control programs. Our review suggests that free-ranging, non-human primates may be involved in ZIKV transmission in the Old World; however, other wildlife species likely play a limited role in maintaining or transmitting ZIKV. In the Americas, a zoonotic cycle has not yet been definitively established. Understanding behaviors and habitat tolerances of Aedes aegypti and Aedes albopictus , two ZIKV competent vectors in the Americas, will allow more accurate modeling of disease spread and facilitate targeted and effective control efforts. Vector control efforts may have direct and indirect impacts to wildlife, particularly invertebrate feeding species; however, strategies could be implemented to limit detrimental ecological effects.

EcoHealth↗

USGS2017

Autonomous acoustic recorders reveal complex patterns in avian detection probability

Avian point‐count surveys are typically designed to occur during periods when birds are consistently active and singing, but seasonal and diurnal patterns of detection probability are often not well understood and may vary regionally or between years. We deployed autonomous acoustic recorders to assess how avian availability for detection (i.e., the probability that a bird signals its presence during a recording) varied during the breeding season with time of day, date, and weather‐related variables at multiple subarctic tundra sites in Alaska, USA, 2013–2014. A single observer processed 2,692 10‐minute recordings across 11 site‐years. We used time‐removal methods to assess availability and used generalized additive models to examine patterns of detectability (joint probability of presence, availability, and detection) for 16 common species. Despite lack of distinct dawn or dusk, most species displayed circadian vocalization patterns, with detection rates generally peaking between 0800 hours and 1200 hours but remaining high as late as 2000 hours for some species. Between 2200 hours and 0500 hours, most species’ detection rates dropped to near 0, signaling a distinctive rest period. Detectability dropped sharply for most species in early July. For all species considered, time‐removal analysis indicated nearly 100% likelihood of detection during a 10‐minute recording conducted in June, between 0500 hours and 2000 hours. This indicates that non‐detections during appropriate survey times and dates were attributable to the species’ absence or that silent birds were unlikely to initiate singing during a 10‐minute interval, whereas vocally active birds were singing very frequently. Systematic recordings revealed a gradient of species’ presence at each site, from ubiquitous to incidental. Although the total number of species detected at a site ranged from 16 to 27, we detected only 4 to 15 species on ≥5% of the site's recordings. Recordings provided an unusually detailed and consistent dataset that allowed us to identify, among other things, appropriate survey dates and times for species breeding at northern latitudes. Our results also indicated that more recordings of shorter duration (1–4 min) may be most efficient for detecting passerines.

Journal of Wildlife Management↗

USGS2016

When winners become losers: Predicted nonlinear responses of arctic birds to increasing woody vegetation

Climate change is facilitating rapid changes in the composition and distribution of vegetation at northern latitudes, raising questions about the responses of wildlife that rely on arctic ecosystems. One widely observed change occurring in arctic tundra ecosystems is an increasing dominance of deciduous shrub vegetation. Our goals were to examine the tolerance of arctic-nesting bird species to existing gradients of vegetation along the boreal forest-tundra ecotone, to predict the abundance of species across different heights and densities of shrubs, and to identify species that will be most or least responsive to ongoing expansion of shrubs in tundra ecosystems. We conducted 1,208 point counts on 12 study blocks from 2012–2014 in northwestern Alaska, using repeated surveys to account for imperfect detection of birds. We considered the importance of shrub height, density of low and tall shrubs (i.e. shrubs >0.5 m tall), percent of ground cover attributed to shrubs (including dwarf shrubs <0.5 m tall), and percent of herbaceous plant cover in predicting bird abundance. Among 17 species considered, only gray-cheeked thrush ( Catharus minimus ) abundance was associated with the highest values of all shrub metrics in its top predictive model. All other species either declined in abundance in response to one or more shrub metrics or reached a threshold where further increases in shrubs did not contribute to greater abundance. In many instances the relationship between avian abundance and shrubs was nonlinear, with predicted abundance peaking at moderate values of the covariate, then declining at high values. In particular, a large number of species were responsive to increasing values of average shrub height with six species having highest abundance at near-zero values of shrub height and abundance of four other species decreasing once heights reached moderate values (≤ 33 cm). Our findings suggest that increases in shrub cover and density will negatively affect abundance of only a few bird species and may potentially be beneficial for many others. As shrub height increases further, however, a considerable number of tundra bird species will likely find habitat increasingly unsuitable.

Alaska↗

USGS2015

Avoidance of unconventional oil wells and roads exacerbates habitat loss for grassland birds in the North American great plains

Oil development in the Bakken shale region has increased rapidly as a result of new technologies and strong demand for fossil fuel. This region also supports a particularly high density and diversity of grassland bird species, which are declining across North America. We examined grassland bird response to unconventional oil extraction sites (i.e. developed with hydraulic fracturing and horizontal drilling techniques) and associated roads in North Dakota. Our goal was to quantify the amount of habitat that was indirectly degraded by oil development, as evidenced by patterns of avoidance by birds. Grassland birds avoided areas within 150 m of roads (95% CI: 87–214 m), 267 m of single-bore well pads (95% CI: 157–378 m), and 150 m of multi-bore well pads (95% CI: 67–233 m). Individual species demonstrated variable tolerance of well pads. Clay-colored sparrows ( Spizella pallida ) were tolerant of oil-related infrastructure, whereas Sprague's pipit ( Anthus spragueii ) avoided areas within 350 m (95% CI: 215–485 m) of single-bore well pads. Given these density patterns around oil wells, the potential footprint of any individual oil well, and oil development across the region, is greatly multiplied for sensitive species. Efforts to reduce new road construction, concentrate wells along developed corridors, combine numerous wells on multi-bore pads rather than build many single-bore wells, and to place well pads near existing roads will serve to minimize loss of suitable habitat for birds. Quantifying environmental degradation caused by oil development is a critical step in understanding how to better mitigate harm to wildlife populations.

Biological Conservation↗

USGS2014

A multiscale assessment of tree avoidance by prairie birds

In North America, grassland bird abundances have declined, likely as a result of loss and degradation of prairie habitat. Given the expense and limited opportunity to procure new grasslands, managers are increasingly focusing on ways to improve existing habitat for grassland birds, using techniques such as tree removal. To examine the potential for tree removal to benefit grassland birds, we conducted 446 point counts on 35 grassland habitat patches in the highly fragmented landscape of west-central Minnesota during 2009–2011. We modeled density of four grassland bird species in relation to habitat composition at multiple scales, focusing on covariates that described grass, woody vegetation (trees and large shrubs), or combinations of grass and woody vegetation. The best-supported models for all four grassland bird species incorporated variables measured at multiple scales, including local features such as grass height, litter depth, and local tree abundance, as well as landscape-level measures of grass and tree cover. Savannah Sparrows ( Passerculus sandwichensis ), Sedge Wrens ( Cistothorus platensis ), and Bobolinks ( Dolichonyx oryzivorus ) responded consistently and negatively to woody vegetation, but response to litter depth, grass height, and grassland extent were mixed among species. Our results suggest that reducing shrub and tree cover is more likely to increase the density of grassland birds than are attempts to improve grass quality or quantity. In particular, tree removal is more likely to increase density of Savannah Sparrows and Sedge Wrens than any reasonable changes in grass quality or quantity. Yet tree removal may not result in increased abundance of grassland birds if habitat composition is not considered at multiple scales. Managers will need to either manage at large scales (80–300 ha) or focus their efforts on removing trees in landscapes that contain some grasslands but few nearby wooded areas.

Minnesota↗