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At least 631 records · Page 35Linked to original sources
USGS2022

Spatial and temporal distribution and habitat selection of native Yellowstone Cutthroat Trout and nonnative Utah Chub

Henrys Lake, Idaho, is a renowned trophy trout fishery that faces an uncertain future following the establishment of Utah Chub (UTC) Gila atraria . Utah Chub were first documented in the lake in 1993 and have become abundant over the past two decades. Little is known about the ecology of UTC, but they typically have negative effects on salmonids in systems where they have been introduced. We sought to fill knowledge gaps in UTC ecology and provide insight on potential interactions with Yellowstone Cutthroat Trout (YCT) Oncorhynchus clarkii bouvieri . Ninety-four YCT and 95 UTC were radio-tagged in spring 2019 and 2020 to better understand potential interactions between YCT and UTC in Henrys Lake. Fish were located via mobile tracking and fixed receivers from June to December 2019 and 2020. In June of both years, YCT and UTC were concentrated in nearshore habitats. As water temperatures increased, UTC were documented in deeper water (mean ± SD = 3.6 ± 1.4 m) and YCT became more concentrated in areas with cold water (e.g., mouths of tributaries, in-lake springs). In July and August, large congregations of UTC were observed. Yellowstone Cutthroat Trout were detected in tributaries from June to August, but no UTC were detected in the tributaries. By late fall (November–December), YCT were located along the shoreline and UTC were detected in the middle of the lake. Both YCT and UTC were observed in areas with dense vegetation. Macrophytes likely provided a food source for UTC and cover from predators for both species. Locations of YCT were negatively related to warm water temperatures, whereas UTC were positively associated with warm water temperatures. Results from this research fill knowledge gaps in UTC and YCT interactions as well as provide valuable insight on the ecology of UTC and adfluvial Cutthroat Trout populations. Furthermore, distribution patterns and habitat selectivity of YCT and UTC in Henrys Lake can be used to inform management decisions for fishery improvement and YCT conservation.

Idaho↗
USGS1989

Interaction assessment: Rationale and a test using plants

A non-manipulative method for deriving empirical expressions of population growth parameters from simple field data is presented. The derived expressions can be used to assess the intensity and form of density dependence and interspecies interactions, and have potential for parameterizing more mechanistic models of population dynamics and for use in applied ecology, e.g. land management or environmental risk assessment. The method is based on an assertion of invariant expected fitness across occupied microhabitats. Hence, its success depends upon the degree to which that assertion holds. The assertion, as used here, is broadly applicable. Thus, the method can be expected to yield reliable results even in nonequilibrium communities. Here, we apply the method to data on six desert plant species. Expressions generated from data in one stand, in one year, successfully predict plant cover values in other stands and years. The predicted patterns of plant species interactions are discussed in the light of current knowledge and theorics of desert succession.

Evolutionary Ecology↗
USGS2017

Landscape capability models as a tool to predict fine-scale forest bird occupancy and abundance

Context Species-specific models of landscape capability (LC) can inform landscape conservation design. Landscape capability is “the ability of the landscape to provide the environment […] and the local resources […] needed for survival and reproduction […] in sufficient quantity, quality and accessibility to meet the life history requirements of individuals and local populations.” Landscape capability incorporates species’ life histories, ecologies, and distributions to model habitat for current and future landscapes and climates as a proactive strategy for conservation planning. Objectives We tested the ability of a set of LC models to explain variation in point occupancy and abundance for seven bird species representative of spruce-fir, mixed conifer-hardwood, and riparian and wooded wetland macrohabitats. Methods We compiled point count data sets used for biological inventory, species monitoring, and field studies across the northeastern United States to create an independent validation data set. Our validation explicitly accounted for underestimation in validation data using joint distance and time removal sampling. Results Blackpoll warbler ( Setophaga striata ), wood thrush ( Hylocichla mustelina ), and Louisiana ( Parkesia motacilla ) and northern waterthrush ( P. noveboracensis ) models were validated as predicting variation in abundance, although this varied from not biologically meaningful (1%) to strongly meaningful (59%). We verified all seven species models [including ovenbird ( Seiurus aurocapilla ), blackburnian ( Setophaga fusca ) and cerulean warbler ( Setophaga cerulea )], as all were positively related to occupancy data. Conclusions LC models represent a useful tool for conservation planning owing to their predictive ability over a regional extent. As improved remote-sensed data become available, LC layers are updated, which will improve predictions.

Landscape Ecology↗
USGS2016

Molecular detection of bacteria in the families Rickettsiaceae and Anaplasmataceae in northern crested caracaras ( Caracara cheriway )

Bacterial pathogens of the families Anaplasmataceae and Rickettsiaceae are often spread to humans or other animals from bites from infected arthropod hosts. Recently, an increasing number of studies have implicated migratory birds in the circulation of these pathogens through the spread of arthropod vectors. However, few studies have examined the potential for resident bird populations to serve as reservoirs for these zoonoses. In this study, we used nested PCRs of the GroESL and 17 kDa genes to screen for Anaplasmataceae and Rickettsiaceae , respectively, in a resident population of the northern crested caracara ( Caracara cheriway ) from Florida ( n = 55). Additionally, a small number ( n = 6) of captive individuals from Texas were included. We identified one individual (1.64%) positive for Rickettsia felis and one (1.64%) positive for Ehrlichia chaffeensis; both these individuals were from Florida. Presence of these pathogens demonstrates that these birds are potential hosts; however, the low prevalence of infections suggests that these populations likely do not function as an ecological reservoir.

Ticks and Tick-borne Diseases↗
USGS2013

Infectious diseases of fishes in the Salish Sea

As in marine regions throughout other areas of the world, fishes in the Salish Sea serve as hosts for many pathogens, including nematodes, trematodes, protozoans, protists, bacteria, viruses, and crustaceans. Here, we review some of the better-documented infectious diseases that likely contribute to significant losses among free-ranging fishes in the Salish Sea and discuss the environmental and ecological factors that may affect the population-level impacts of disease. Demonstration of these diseases and their impacts to critical and endangered resources provides justification to expand pathogen surveillance efforts and to incorporate disease forecasting and mitigation tools into ecosystem restoration efforts.

Washington↗
USGS2019

Flexible timing of annual movements across consistently used sites by Marbled Godwits breeding in Alaska

The study of avian movement has detailed a spectrum of strategies for the timing and use of sites throughout the annual cycle, from near randomness to complete consistency. New tracking devices now permit the repeated tracking of individual animals throughout the annual cycle, detailing previously unappreciated levels of variation within migratory systems. Godwits (genus Limosa ) have featured prominently in studies of avian migration, but information derived from repeated tracking of individuals is limited. The Marbled Godwit subspecies Limosa fedoa beringiae breeds on the central Alaska Peninsula, and little is known about basic aspects of its migration ecology, including the repeatability with which this population times its annual migratory movements or uses migratory and nonbreeding sites. To address these questions, we equipped 9 Marbled Godwits breeding at a site near Ugashik, Alaska, with solar-powered satellite transmitters. We tracked individuals from July, 2008 to October, 2015 and obtained repeat migratory tracks from 5 of these birds. Individuals exhibited high fidelity to breeding, nonbreeding, and migratory stopover sites across years, but in contrast to congeners that conduct consistently timed, long, nonstop migrations, beringiae Marbled Godwits exhibited low levels of individual- or population-level repeatability in the timing of migratory movements. Their relatively short migrations may enable the integration of local environmental cues, potentially facilitating individual flexibility in the timing of annual migratory movements. Curiously, if local cues ultimately drive the timing of Marbled Godwit migratory movements, the population’s relatively constrained distribution during both the breeding and nonbreeding season should serve to synchronize birds if they are responding to similar cues. That our sample of Marbled Godwits nonetheless exhibited within- and between-year variation in the timing of their migratory movements suggests a complex integration of annually variable internal and external cues.

The Auk↗
USGS2024

The potential for species distribution models to distinguish source populations from sinks

1. While species distribution models (SDM) are frequently used to predict species occurrences to help inform conservation management, there is limited evidence evaluating whether habitat suitability can reliably predict intrinsic growth rates or distinguish source from sink populations. Filling this knowledge gap is critical for conservation science, as applications of SDMs for management purposes ultimately depend on these typically unobserved population or metapopulation dynamics. 2. Using regression, we associate previously published population level estimates of intrinsic growth and abundance derived from a Bayesian analysis of mark-recapture data for 17 bird species found in the contiguous United States with SDM habitat suitability estimates fitted here to opportunistic data for these same species. We then use AUC to measure how well SDMs can distinguish populations categorized as sources and sinks, depending on their intrinsic growth rates estimated from the mark-recapture data. We built SDMs using two different approaches, boosted regression trees (BRT) and Generalized Linear Models (GLM), and compared their predictive performance. Each SDM was built with presence points obtained from eBird and 10 environmental variables previously selected to model intrinsic growth rates and abundance for these species. 3. We show that SDMs built with opportunistic data are poor predictors of species demography in general; both BRT and GLM explained very little spatial variation of intrinsic growth rate and population abundance (median R2 across 17 species was close to 0.1 for both SDM methods). SDMs do, however, estimate higher suitability for source populations as compared to sinks. Out of 13 species which had both source and sink populations, both BRT and GLM had AUC values greater than 0.7 for 7 species when discriminating between sources and sinks. 4. Habitat suitability have the potential to be a useful measure to indicate a population’s ability to sustain itself as a source population, however more research on a diverse set of taxa is essential to fully explore this potential. This interpretation of habitat suitability can be particularly useful for conservation practice, and identification of explicit cases of when and how SDMs fail to match population demography can be informative for advancing ecological theory.

Journal of Animal Ecology↗
USGS2017

Estimating occupancy and abundance using aerial images with imperfect detection

Species distribution and abundance are critical population characteristics for efficient management, conservation, and ecological insight. Point process models are a powerful tool for modelling distribution and abundance, and can incorporate many data types, including count data, presence-absence data, and presence-only data. Aerial photographic images are a natural tool for collecting data to fit point process models, but aerial images do not always capture all animals that are present at a site. Methods for estimating detection probability for aerial surveys usually include collecting auxiliary data to estimate the proportion of time animals are available to be detected. We developed an approach for fitting point process models using an N -mixture model framework to estimate detection probability for aerial occupancy and abundance surveys. Our method uses multiple aerial images taken of animals at the same spatial location to provide temporal replication of sample sites. The intersection of the images provide multiple counts of individuals at different times. We examined this approach using both simulated and real data of sea otters ( Enhydra lutris kenyoni ) in Glacier Bay National Park, southeastern Alaska. Using our proposed methods, we estimated detection probability of sea otters to be 0.76, the same as visual aerial surveys that have been used in the past. Further, simulations demonstrated that our approach is a promising tool for estimating occupancy, abundance, and detection probability from aerial photographic surveys. Our methods can be readily extended to data collected using unmanned aerial vehicles, as technology and regulations permit. The generality of our methods for other aerial surveys depends on how well surveys can be designed to meet the assumptions of N -mixture models.

Methods in Ecology and Evolution↗
USGS2026

Using structured decision making to evaluate the tradeoffs of selective fish passage

Dams have dramatically altered rivers and are a major contributor to native fish population declines. However, many dams serve important ecological, social, and economic functions, such as flood control, invasive species control, and provision of recreational opportunities. Therefore, dam removal is often contentious among stakeholders and involves making tradeoffs among multiple competing objectives. This research uses structured decision making to evaluate the ecological, social, and economic consequences and tradeoffs of enhancing connectivity for migratory fishes in the Boardman River, Michigan. We describe efforts to engage a diverse group of stakeholders to elicit their objectives under various fish passage alternatives. We used multi-attribute tradeoff methods to help stakeholders weigh the costs and benefits of enhancing connectivity for several fish species with varying life history traits and initial distributions. We found that the optimal alternative was passage of native fishes only; however, the optimal alternative varied based on the weight stakeholders might place on each objective. We created four objective weighting scenarios to evaluate the sensitivity of the optimal alternative to changes in objective weights. This research will help inform decision-makers on fish passage alternatives that are preferred by stakeholders and that are likely to achieve their objectives.

Michigan↗
USGS2014

Comparative reproductive biology of sympatric species: Nest and chick survival of American avocets and black-necked stilts

Identifying differences in reproductive success rates of closely related and sympatrically breeding species can be useful for understanding limitations to population growth. We simultaneously examined the reproductive ecology of American avocets Recurvirostra americana and black-necked stilts Himantopus mexicanus using 1274 monitored nests and 240 radio-marked chicks in San Francisco Bay, California. Although there were 1.8 times more avocet nests than stilt nests, stilts nonetheless fledged 3.3 times more chicks. Greater production by stilts than avocets was the result of greater chick survival from hatching to fledging (avocet: 6%; stilt: 40%), and not because of differences in clutch size (avocet: 3.84; stilt: 3.77), nest survival (avocet: 44%; stilt: 35%), or egg hatching success (avocet: 90%; stilt: 92%). We reviewed the literature and confirmed that nest survival and hatching success are generally similar when avocets and stilts breed sympatrically. In addition to species, chick survival was strongly influenced by age, site, and year. In particular, daily survival rates increased rapidly with chick age, with 70% of mortalities occurring ≤ 1 week after hatch. California gulls Larus californicus caused 55% of avocet, but only 15% of stilt, chick deaths. Differential use of micro-habitats likely reduced stilt chick’s vulnerability to gull predation, particularly during the first week after hatch, because stilts nested in vegetation 2.7 times more often than avocets and vegetation height was 65% taller at stilt nests compared with avocet nests. Our results demonstrate that two co-occurring and closely related species with similar life history strategies can differ markedly in reproductive success, and simultaneous studies of such species can identify differences that limit productivity.

California↗
USGS2015

Conservation planning for offsetting the impacts of development: a case study of biodiversity and renewable energy in the Mojave Desert

Balancing society’s competing needs of development and conservation requires careful consideration of tradeoffs. Renewable energy development and biodiversity conservation are often considered beneficial environmental goals. The direct footprint and disturbance of renewable energy, however, can displace species’ habitat and negatively impact populations and natural communities if sited without ecological consideration. Offsets have emerged as a potentially useful tool to mitigate residual impacts after trying to avoid, minimize, or restore affected sites. Yet the problem of efficiently designing a set of offset sites becomes increasingly complex where many species or many sites are involved. Spatial conservation prioritization tools are designed to handle this problem, but have seen little application to offset siting and analysis. To address this need we designed an offset siting support tool for the Desert Renewable Energy Conservation Plan (DRECP) of California, and present a case study of hypothetical impacts from solar development in the Western Mojave subsection. We compare two offset scenarios designed to mitigate a hypothetical 15,331 ha derived from proposed utility-scale solar energy development (USSED) projects. The first scenario prioritizes offsets based precisely on impacted features, while the second scenario offsets impacts to maximize biodiversity conservation gains in the region. The two methods only agree on 28% of their prioritized sites and differ in meeting species-specific offset goals. Differences between the two scenarios highlight the importance of clearly specifying choices and priorities for offset siting and mitigation in general. Similarly, the effects of background climate and land use change may lessen the durability or effectiveness of offsets if not considered. Our offset siting support tool was designed specifically for the DRECP area, but with minor code modification could work well in other offset analyses, and could provide continuing support for a potentially innovative mitigation solution to environmental impacts.

California↗
USGS2005

Nest survival relative to patch size in a highly fragmented shortgrass prairie landscape

Understanding the influences of habitat fragmentation on vertebrate populations is essential for the protection and ecological restoration of strategic sites for native species. We examined the effects of prairie fragmentation on avian reproductive success using artificial and natural nests on 26 randomly selected, privately owned patches of shortgrass prairie ranging in size from 7 to 454 ha within a cropland matrix in Washington County, Colorado, summer 2000. Survival trends of artificial and natural nests differed. Daily survival of artificial nests increased with patch size up to about 65 ha and differed little at larger patch sizes, whereas daily survival of Lark Bunting ( Calamospiza melanocorys ) and Horned Lark ( Eremophila alpestris ) nests decreased with increasing size of the grassland patch. We hypothesize that our unexpected findings of lower survival of natural nests with increasing patch sizes and different trends between artificial and natural nests are due to the particular structure of predator communities in our study area and the ways in which individual predators respond to artificial and natural nests. We recommend that the value of small habitat patches in highly fragmented landscapes not be overlooked.

The Wilson Bulletin↗
USGS2010

Tuning stochastic matrix models with hydrologic data to predict the population dynamics of a riverine fish

We developed stochastic matrix models to evaluate the effects of hydrologic alteration and variable mortality on the population dynamics of a lotie fish in a regulated river system. Models were applied to a representative lotic fish species, the flathead catfish (Pylodictis olivaris), for which two populations were examined: a native population from a regulated reach of the Coosa River (Alabama, USA) and an introduced population from an unregulated section of the Ocmulgee River (Georgia, USA). Size-classified matrix models were constructed for both populations, and residuals from catch-curve regressions were used as indices of year class strength (i.e., recruitment). A multiple regression model indicated that recruitment of flathead catfish in the Coosa River was positively related to the frequency of spring pulses between 283 and 566 m 3 /s. For the Ocmulgee River population, multiple regression models indicated that year class strength was negatively related to mean March discharge and positively related to June low flow. When the Coosa population was modeled to experience five consecutive years of favorable hydrologic conditions during a 50-year projection period, it exhibited a substantial spike in size and increased at an overall 0.2% annual rate. When modeled to experience five years of unfavorable hydrologic conditions, the Coosa population initially exhibited a decrease in size but later stabilized and increased at a 0.4% annual rate following the decline. When the Ocmulgee River population was modeled to experience five years of favorable conditions, it exhibited a substantial spike in size and increased at an overall 0.4% annual rate. After the Ocmulgee population experienced five years of unfavorable conditions, a sharp decline in population size was predicted. However, the population quickly recovered, with population size increasing at a 0.3% annual rate following the decline. In general, stochastic population growth in the Ocmulgee River was more erratic and variable than population growth in the Coosa River. We encourage ecologists to develop similar models for other lotic species, particularly in regulated river systems. Successful management of fish populations in regulated systems requires that we are able to predict how hydrology affects recruitment and will ultimately influence the population dynamics of fishes. ?? 2010 by the Ecological Society of America.

Ecological Applications↗
USGS2017

U.S. Geological Survey Cooperative Fish and Wildlife Research Units Program—2016–2017 Research Abstracts

The U.S. Geological Survey (USGS) has several strategic goals that focus its efforts on serving the American people. The USGS Ecosystems Mission Area has responsibility for the following objectives under the strategic goal of “Science to Manage and Sustain Resources for Thriving Economies and Healthy Ecosystems”: Understand, model, and predict change in natural systems Conserve and protect wildlife and fish species and their habitats Reduce or eliminate the threat of invasive species and wildlife disease This report provides abstracts of the majority of ongoing research investigations of the USGS Cooperative Fish and Wildlife Research Units program and is intended to complement the 2016 Cooperative Research Units Program Year in Review Circular 1424 ( https://doi.org/10.3133/cir1424 ). The report is organized by the following major science themes that contribute to the objectives of the USGS: Advanced Technologies Climate Science Decision Science Ecological Flows Ecosystem Services Endangered Species Conservation, Recovery, and Proactive Strategies Energy Human Dimensions Invasive Species Landscape Ecology Species of Greatest Conservation Need Species Population, Habitat, and Harvest Management Wildlife Health and Disease

Circular↗
USGS2017

Hierarchical population monitoring of greater sage-grouse ( Centrocercus urophasianus ) in Nevada and California—Identifying populations for management at the appropriate spatial scale

Population ecologists have long recognized the importance of ecological scale in understanding processes that guide observed demographic patterns for wildlife species. However, directly incorporating spatial and temporal scale into monitoring strategies that detect whether trajectories are driven by local or regional factors is challenging and rarely implemented. Identifying the appropriate scale is critical to the development of management actions that can attenuate or reverse population declines. We describe a novel example of a monitoring framework for estimating annual rates of population change for greater sage-grouse ( Centrocercus urophasianus ) within a hierarchical and spatially nested structure. Specifically, we conducted Bayesian analyses on a 17-year dataset (2000–2016) of lek counts in Nevada and northeastern California to estimate annual rates of population change, and compared trends across nested spatial scales. We identified leks and larger scale populations in immediate need of management, based on the occurrence of two criteria: (1) crossing of a destabilizing threshold designed to identify significant rates of population decline at a particular nested scale; and (2) crossing of decoupling thresholds designed to identify rates of population decline at smaller scales that decouple from rates of population change at a larger spatial scale. This approach establishes how declines affected by local disturbances can be separated from those operating at larger scales (for example, broad-scale wildfire and region-wide drought). Given the threshold output from our analysis, this adaptive management framework can be implemented readily and annually to facilitate responsive and effective actions for sage-grouse populations in the Great Basin. The rules of the framework can also be modified to identify populations responding positively to management action or demonstrating strong resilience to disturbance. Similar hierarchical approaches might be beneficial for other species occupying landscapes with heterogeneous disturbance and climatic regimes.

California, Nevada↗
USGS2001

The Foraging Ecology of Royal and Sandwich Terns in North Carolina, USA

Population sizes of territorial male red-winged blackbirds (Agelaius phoeniceus) were determined with counts of territorial males (area count) and a Petersen-Lincoln Index method for roadsides (roadside estimate). Weather conditions and time of day did not influence either method. Combined roadside estimates had smaller error bounds than the individual transect estimates and were not hindered by the problem of zero recaptures. Roadside estimates were usually one-half as large as the area counts, presumably due to an observer bias for marked birds. The roadside estimate provides only an index of major changes in populations of territorial male redwings. When the roadside estimate is employed, the area count should be used to determine the amount and nature of observer bias. For small population surveys, the area count is probably more reliable and accurate than the roadside estimate.

Waterbirds↗
USGS2002

Evaluation of genetic variability in a small, insular population of spruce grouse

Using microsatellite markers we determined genetic variability for two populations of spruce grouse in eastern North America, one on a coastal Maine island where breeding habitat is limited and highly fragmented, the other in central New Brunswick (NB), where suitable breeding habitat is generally contiguous across the region. We examined six markers for both populations and all were polymorphic. Although the number of alleles per locus and the proportion of unique alleles were lower in the island population, and probably a result of small sample.size, heterozygosity and a breeding coefficient (Fis) indicated slightly more variability in the island population. Deviation from Hardy-Weinberg equilibrium also was more evident in loci for the mainland population. Several traits previously documented in the island population: relatively long natal dispersal distances, reproductive success, territoriality, adult survival, and longevity support the maintenance of hetrerzygosity, at least in the short-term. Sample collection from two small (500 ha), separate areas in NB, and the predicted importance of immigration density to supplement this population demonstrate the need for behavioral and ecological information when interpreting genetic variation. We discuss the relevance of these issues with respect to genetic variability and viability.

Book chapter↗
USGS2006

Demographic patterns of postfire regeneration in Mediterranean-climate shrublands of California

This study uses detailed demographic data to determine the extent to which functional groupings, based on seedling recruitment and resprouting response to fire, capture the dynamics of postfire responses and early successional change in fire-prone ecosystems. Following massive wildfires in southern California, USA, we sampled chaparral and sage scrub vegetation in nested 0.1-ha plots from 90 sites for five postfire years. Prefire density of woody skeletons and cover and density of all postfire species were recorded. Functional types of postfire obligate seeder, facultative seeder, and obligate resprouter are broadly useful but fail to capture much of the dynamics of postfire succession in these shrublands. For the woody flora, stratifying these three regeneration modes by life-form captures important differences. Postfire obligate-seeding shrubs exhibit a single postfire seedling cohort whereas the faster growing suffrutescent species reach reproductive maturity by the second year and produce multiple seedling cohorts. Postfire obligate-resprouting shrubs reach reproductive maturity early but have very limited seedling recruitment in the early postfire years, whereas obligate-resprouting subshrubs flower the first year from resprouts and have seedling recruitment pulses in the second and subsequent postfire years. For the rich herbaceous flora, further subdivisions are needed to capture the range of variation. Herbaceous perennials are nearly all postfire obligate resprouters, and there are important demographic differences during early succession in different growth forms such as geophytes and rhizomatous grasses. Annuals lack resprouting ability and are postfire obligate seeders. Some exhibit extreme life-history specialization and are present only in the immediate postfire year(s). Others are highly specialized on fire but persist during early succession, and still others are opportunistic species widely distributed on open sites but can expand their populations during early succession. ?? 2006 by the Ecological Society of America.

Ecological Monographs↗