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At least 37 records · Page 2Linked to original sources
USGS2004

Fort Collins Science Center: Species and Habitats of Federal Interest

Ecosystem changes directly affect a wide variety of plant and animal species, floral and faunal communities, and groups of species such as amphibians and grassland birds. Appropriate management of public lands plays a crucial role in the conservation and recovery of endangered species and can be a key element in preventing a species from being listed under the Endangered Species Act. The Species and Habitats of Federal Interest Branch of the Fort Collins Science Center (FORT) conducts research on the ecology, habitat requirements, distribution and abundance, population dynamics, and genetics and systematics of many species facing threatened or endangered status or of special concern to resource management agencies. FORT scientists develop reintroduction and restoration techniques, technologies for monitoring populations, and novel methods to analyze data on population trends and habitat requirements. FORT expertise encompasses both traditional and specialized natural resource disciplines within wildlife biology, including population dynamics, animal behavior, plant and community ecology, inventory and monitoring, statistics and computer applications, conservation genetics, stable isotope analysis, and curatorial expertise.

Fact Sheet↗
USGS2015

Trust Species and Habitat Branch: using the innovative approaches of today to conserve biodiversity for tomorrow

Some of the biggest challenges facing wildlife today are changes to their environment from both natural and anthropogenic causes. Natural resource managers, planners, policy makers, industry and private landowners must make informed decisions and policies regarding management, conservation, and restoration of species, habitats, and ecosystem function in response to these changes. Specific needs include (1) a better understanding of population status and trends; (2) understanding of species’ habitat needs and roles in supporting ecosystem functions; (3) the ability to assess species’ responses to environmental changes and predict future responses; and (4) the development of innovative techniques and tools to better understand, minimize or prevent any unintended consequences of environmental change. The Trust Species and Habitats Branch of the Fort Collins Science Center includes a diverse group of scientists encompassing both traditional and specialized expertise in wildlife biology, ecosystem ecology, quantitative ecology, disease ecology, molecular genetics, and stable isotope geochemistry. Using our expertise and collaborating with others around the world, our goal is to provide the information, tools, and technologies that our partners need to support conservation, management, and restoration of terrestrial vertebrate populations, habitats, and ecosystem function in a changing world.

Fact Sheet↗
USGS2009

Simulation of streamflow using a multidimensional flow model for white sturgeon habitat, Kootenai River near Bonners Ferry, Idaho – Supplement to Scientific Investigations Report 2005-5230

During 2005, the U.S. Geological Survey (USGS) developed, calibrated, and validated a multidimensional flow model for simulating streamflow in the white sturgeon spawning habitat of the Kootenai River in Idaho. The model was developed as a tool to aid understanding of the physical factors affecting quality and quantity of spawning and rearing habitat used by the endangered white sturgeon (Acipenser transmontanus) and for assessing the feasibility of various habitat-enhancement scenarios to re-establish recruitment of white sturgeon. At the request of the Kootenai Tribe of Idaho, the USGS extended the two-dimensional flow model developed in 2005 into a braided reach upstream of the current white sturgeon spawning reach. Many scientists consider the braided reach a suitable substrate with adequate streamflow velocities for re-establishing recruitment of white sturgeon. The 2005 model was extended upstream to help assess the feasibility of various strategies to encourage white sturgeon to spawn in the reach. At the request of the Idaho Department of Fish and Game, the USGS also extended the two-dimensional flow model several kilometers downstream of the white sturgeon spawning reach. This modified model can quantify the physical characteristics of a reach that white sturgeon pass through as they swim upstream from Kootenay Lake to the spawning reach. The USGS Multi-Dimensional Surface-Water Modeling System was used for the 2005 modeling effort and for this subsequent modeling effort. This report describes the model applications and limitations, presents the results of a few simple simulations, and demonstrates how the model can be used to link physical characteristics of streamflow to the location of white sturgeon spawning events during 1994-2001. Model simulations also were used to report on the length and percentage of longitudinal profiles that met the minimum criteria during May and June 2006 and 2007 as stipulated in the U.S. Fish and Wildlife Biological Opinion.

Idaho↗
USGS2006

Model weights and the foundations of multimodel inference

Statistical thinking in wildlife biology and ecology has been profoundly influenced by the introduction of AIC (Akaike?s information criterion) as a tool for model selection and as a basis for model averaging. In this paper, we advocate the Bayesian paradigm as a broader framework for multimodel inference, one in which model averaging and model selection are naturally linked, and in which the performance of AIC-based tools is naturally evaluated. Prior model weights implicitly associated with the use of AIC are seen to highly favor complex models: in some cases, all but the most highly parameterized models in the model set are virtually ignored a priori. We suggest the usefulness of the weighted BIC (Bayesian information criterion) as a computationally simple alternative to AIC, based on explicit selection of prior model probabilities rather than acceptance of default priors associated with AIC. We note, however, that both procedures are only approximate to the use of exact Bayes factors. We discuss and illustrate technical difficulties associated with Bayes factors, and suggest approaches to avoiding these difficulties in the context of model selection for a logistic regression. Our example highlights the predisposition of AIC weighting to favor complex models and suggests a need for caution in using the BIC for computing approximate posterior model weights.

Ecology↗
USGS2025

Integrating climate change, biological invasions, and infectious wildlife diseases

Climate change is likely to affect infectious diseases that are facilitated by biological invasions, with repercussions for wildlife conservation and zoonotic risks. Current invasion management and policy are underprepared for the future risks associated with such invasion-related wildlife diseases. By considering evidence from bioclimatology, invasion biology, and disease research, we illustrate how climate change is anticipated to affect disease agents (parasites and pathogens), hosts, and vectors across the different stages of invasions. We highlight the opportunity to integrate these disciplines to identify the effects of climate change on invasion related wildlife diseases. In addition, shifting to a proactive stance in implementing management and policy, such as by incorporating climate-change effects either into preventative and mitigation measures for biosecurity or with rapid response protocols to limit disease spread and impacts, could help to combat future ecological, economic, and human health risks stemming from invasion-related wildlife diseases.

Frontiers in Ecology and the Environment↗
USGS2007

Optimal management of non-Markovian biological populations

Wildlife populations typically are described by Markovian models, with population dynamics influenced at each point in time by current but not previous population levels. Considerable work has been done on identifying optimal management strategies under the Markovian assumption. In this paper we generalize this work to non-Markovian systems, for which population responses to management are influenced by lagged as well as current status and/or controls. We use the maximum principle of optimal control theory to derive conditions for the optimal management such a system, and illustrate the effects of lags on the structure of optimal habitat strategies for a predator-prey system.

Ecological Modelling↗
USGS1993

In my experience: Mitochondrial DNA in wildlife taxonomy and conservation biology: Cautionary notes

Several recently published papers discussed the importance of systematics (the study of evolutionary and genetic relationships among organisms) and taxonomy (the naming and classification of organisms) for managing wildlife (Ryder 1986, Avise 1989, Amato 1991, O'Brien and Mayr 1991, Dowling et al. 1992), Often, classification below the species level is needed; for example, the Endangered Species Act of 1973 applies to local populations and subspecies as well as species. Conservation efforts may focus below the species level because of concerns about the fitness, evolutionary potentials, and locally adapted gene pools of natural populations (Soulé 1986, Hedrick and Milller 1992). This can be considered the genetic component of biodiversity. Recent systematic studies with wildlife management applications have used modern molecular genetic methods. Analyses of a specific molecular marker, mitochondrial DNA (mtDNA), have been used in many of these studies (e.g., Shields and Wilson 1987, Avise and Nelson 1989, O'Brien et al. 1990, Wayne and Jenks 1991, Cronin 1992), However, there are limitations to the use of mtDNA in systematics (e.g., Overden et al., 1987, Pamilo and Nei 1988, Dowling et al. 1992). In my experience as a geneticist working with wildlife biologists, I have found a need for clarification of the use and limitations of modern molecular genetics. I specifically discuss the limitations of mtDNA data in systematic assessments of wildlife at and below the species level.

Wildlife Society Bulletin↗
USGS2010

Uncovering a latent multinomial: Analysis of mark–recapture data with misidentification

Natural tags based on DNA fingerprints or natural features of animals are now becoming very widely used in wildlife population biology. However, classic capture-recapture models do not allow for misidentification of animals which is a potentially very serious problem with natural tags. Statistical analysis of misidentification processes is extremely difficult using traditional likelihood methods but is easily handled using Bayesian methods. We present a general framework for Bayesian analysis of categorical data arising from a latent multinomial distribution. Although our work is motivated by a specific model for misidentification in closed population capture-recapture analyses, with crucial assumptions which may not always be appropriate, the methods we develop extend naturally to a variety of other models with similar structure. Suppose that observed frequencies f are a known linear transformation f=A'x of a latent multinomial variable x with cell probability vector pi= pi(theta). Given that full conditional distributions [theta | x] can be sampled, implementation of Gibbs sampling requires only that we can sample from the full conditional distribution [x | f, theta], which is made possible by knowledge of the null space of A'. We illustrate the approach using two data sets with individual misidentification, one simulated, the other summarizing recapture data for salamanders based on natural marks.

Biometrics↗
USGS2019

Current state of knowledge on biological effects from contaminants on arctic wildlife and fish

Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to organohalogen compounds (OHCs) in Arctic biota, there has been a considerable number of new Arctic effect studies. Here, we provide an update on the state of the knowledge of OHC, and also include mercury, exposure and/or associated effects in key Arctic marine and terrestrial mammal and bird species as well as in fish by reviewing the literature published since the last AMAP assessment in 2010. We aimed at updating the knowledge of how single but also combined health effects are or can be associated to the exposure to single compounds or mixtures of OHCs. We also focussed on assessing both potential individual as well as population health impacts using population-specific exposure data post 2000. We have identified quantifiable effects on vitamin metabolism, immune functioning, thyroid and steroid hormone balances, oxidative stress, tissue pathology, and reproduction. As with the previous assessment, a wealth of documentation is available for biological effects in marine mammals and seabirds, and sentinel species such as the sledge dog and Arctic fox, but information for terrestrial vertebrates and fish remain scarce. While hormones and vitamins are thoroughly studied, oxidative stress, immunotoxic and reproductive effects need further investigation. Depending on the species and population, some OHCs and mercury tissue contaminant burdens post 2000 were observed to be high enough to exceed putative risk threshold levels that have been previously estimated for non-target species or populations outside the Arctic. In this assessment, we made use of risk quotient calculations to summarize the cumulative effects of different OHC classes and mercury for which critical body burdens can be estimated for wildlife across the Arctic. As our ultimate goal is to better predict or estimate the effects of OHCs and mercury in Arctic wildlife at the individual, population and ecosystem level, there remain numerous knowledge gaps on the biological effects of exposure in Arctic biota. These knowledge gaps include the establishment of concentration thresholds for individual compounds as well as for realistic cocktail mixtures that in fact indicate biologically relevant, and not statistically determined, health effects for specific species and subpopulations. Finally, we provide future perspectives on understanding Arctic wildlife health using new in vivo, in vitro, and in silico techniques, and provide case studies on multiple stressors to show that future assessments would benefit from significant efforts to integrate human health, wildlife ecology and retrospective and forecasting aspects into assessing the biological effects of OHC and mercury exposure in Arctic wildlife and fish.

Science of the Total Environment↗
USGS2006

A system to evaluate the scientific quality of biological and restoration objectives using National Wildlife Refuge Comprehensive Conservation Plans as a case study

It is widely accepted that plans for restoration projects should contain specific, measurable, and science-based objectives to guide restoration efforts. The United States Fish and Wildlife Service (USFWS) is in the process of developing Comprehensive Conservation Plans (CCPs) for more than 500 units in the National Wildlife Refuge System (NWRS). These plans contain objectives for biological and ecosystem restoration efforts on the refuges. Based on USFWS policy, a system was developed to evaluate the scientific quality of such objectives based on three critical factors: (1) Is the objective specific, measurable, achievable, results-oriented, and time-fixed? (2) What is the extent of the rationale that explains the assumptions, logic, and reasoning for the objective? (3) How well was available science used in the development of the objective? The evaluation system scores each factor on a scale of 1 (poor) to 4 (excellent) according to detailed criteria. The biological and restoration objectives from CCPs published as of September 2004 (60 total) were evaluated. The overall average score for all biological and restoration objectives was 1.73. Average scores for each factor were: Factor 1-1.97; Factor 2-1.86; Factor 3-1.38. The overall scores increased from 1997 to 2004. Future restoration efforts may benefit by using this evaluation system during the process of plan development, to ensure that biological and restoration objectives are of the highest scientific quality possible prior to the implementation of restoration plans, and to allow for improved monitoring and adaptive management.

Journal for Nature Conservation↗
USGS2013

Intraseasonal variation in survival and probable causes of mortality in greater sage-grouse Centrocercus urophasianus

The mortality process is a key component of avian population dynamics, and understanding factors that affect mortality is central to grouse conservation. Populations of greater sage-grouse Centrocercus urophasianus have declined across their range in western North America. We studied cause-specific mortality of radio-marked sage-grouse in Eureka County, Nevada, USA, during two seasons, nesting (2008-2012) and fall (2008-2010), when survival was known to be lower compared to other times of the year. We used known-fate and cumulative incidence function models to estimate weekly survival rates and cumulative risk of cause-specific mortalities, respectively. These methods allowed us to account for temporal variation in sample size and staggered entry of marked individuals into the sample to obtain robust estimates of survival and cause-specific mortality. We monitored 376 individual sage-grouse during the course of our study, and investigated 87 deaths. Predation was the major source of mortality, and accounted for 90% of all mortalities during our study. During the nesting season (1 April - 31 May), the cumulative risk of predation by raptors (0.10; 95% CI: 0.05-0.16) and mammals (0.08; 95% CI: 0.03-013) was relatively equal. In the fall (15 August - 31 October), the cumulative risk of mammal predation was greater (M (mam) = 0.12; 95% CI: 0.04-0.19) than either predation by raptors (M (rap) = 0.05; 95% CI: 0.00-0.10) or hunting harvest (M (hunt) = 0.02; 95% CI: 0.0-0.06). During both seasons, we observed relatively few additional sources of mortality (e.g. collision) and observed no evidence of disease-related mortality (e.g. West Nile Virus). In general, we found little evidence for intraseasonal temporal variation in survival, suggesting that the nesting and fall seasons represent biologically meaningful time intervals with respect to sage-grouse survival.

Nevada↗
USGS2015

Process, policy, and implementation of pool-wide drawdowns on the Upper Mississippi River: a promising approach for ecological restoration of large impounded rivers

The Upper Mississippi River (UMR) has been developed and subsequently managed for commercial navigation by the U.S. Army Corps of Engineers (USACE). The navigation pools created by a series of lock and dams initially provided a complex of aquatic habitats that supported a variety of fish and wildlife. However, biological productivity declined as the pools aged. The River Resources Forum, an advisory body to the St. Paul District of the USACE, established a multiagency Water Level Management Task Force (WLMTF) to evaluate the potential of water level management to improve ecological function and restore the distribution and abundance of fish and wildlife habitat. The WLMTF identified several water level management options and concluded that summer growing season drawdowns at the pool scale offered the greatest potential to provide habitat benefits over a large area. Here we summarize the process followed to plan and implement pool-wide drawdowns on the UMR, including involvement of stakeholders in decision making, addressing requirements to modify reservoir operating plans, development and evaluation of drawdown alternatives, pool selection, establishment of a monitoring plan, interagency coordination, and a public information campaign. Three pool-wide drawdowns were implemented within the St. Paul District and deemed successful in providing ecological benefits without adversely affecting commercial navigation and recreational use of the pools. Insights are provided based on more than 17 years of experience in planning and implementing drawdowns on the UMR.

River Research and Applications↗
USGS2015

Assessing local population vulnerability to wind energy development with branching process models: an application to wind energy development

Quantifying the impact of anthropogenic development on local populations is important for conservation biology and wildlife management. However, these local populations are often subject to demographic stochasticity because of their small population size. Traditional modeling efforts such as population projection matrices do not consider this source of variation whereas individual-based models, which include demographic stochasticity, are computationally intense and lack analytical tractability. One compromise between approaches is branching process models because they accommodate demographic stochasticity and are easily calculated. These models are known within some sub-fields of probability and mathematical ecology but are not often applied in conservation biology and applied ecology. We applied branching process models to quantitatively compare and prioritize species locally vulnerable to the development of wind energy facilities. Specifically, we examined species vulnerability using branching process models for four representative species: A cave bat (a long-lived, low fecundity species), a tree bat (short-lived, moderate fecundity species), a grassland songbird (a short-lived, high fecundity species), and an eagle (a long-lived, slow maturation species). Wind turbine-induced mortality has been observed for all of these species types, raising conservation concerns. We simulated different mortality rates from wind farms while calculating local extinction probabilities. The longer-lived species types (e.g., cave bats and eagles) had much more pronounced transitions from low extinction risk to high extinction risk than short-lived species types (e.g., tree bats and grassland songbirds). High-offspring-producing species types had a much greater variability in baseline risk of extinction than the lower-offspring-producing species types. Long-lived species types may appear stable until a critical level of incidental mortality occurs. After this threshold, the risk of extirpation for a local population may rapidly increase with only minimal increases in wind mortality. Conservation biologists and wildlife managers may need to consider this mortality pattern when issuing take permits and developing monitoring protocols for wind facilities. We also describe how our branching process models may be generalized across a wider range of species for a larger assessment project and then describe how our methods may be applied to other stressors in addition to wind.

Ecosphere↗
USGS2026

Biological and environmental drivers of early life fawn survival in a declining pronghorn population

Pronghorn Antilocapra americana occupy only a portion of their historical range and in Oklahoma occur at the eastern edge of the species' contemporary distribution. Monitoring has suggested pronghorn populations in Oklahoma have declined in recent years. We captured and collared 125 adult females across two winters, monitored them for signs of parturition during each subsequent spring, and then captured and radio-collared 70 fawns ≤ 4 days old. We assessed cause-specific mortality, estimated proportional survival, and visualized survival of fawns through 60 days of life with Kaplan–Meier curves. Nearly 87% of fawn mortalities were attributed to predation, with > 77% of predations attributed to coyotes Canis latrans . Our results indicated that fawn survival was lowest during the first 15 days of life, with 33% of fawns surviving to 15 days and 12% surviving to 60 days. We used known-fate models to evaluate the influence of biological factors (i.e. sex, mass, birth timing), environmental factors (i.e. ambient temperature, precipitation, vegetation), and temporal variation on the probability of early life (i.e. the first 15 days) survival. For each adult female with a collared fawn, we used female space-use patterns for 30 days before and 15 days after parturition to collect environmental covariates. Early life probability of survival was lower for larger fawns, those born earlier in the parturition period (i.e. earlier in the year relative to the range of parturition days), and those with higher pre-parturition temperatures; daily probability of survival decreased with time-since-parturition within the first 15 days of life. Our results indicate poor fawn survival, highlight a potential limitation of population growth, and can inform population management by identifying factors influencing early life fawn survival.

Oklahoma↗
USGS2009

Dietary response of sympatric deer to fire using stable isotope analysis of liver tissue

Carbon (?? 13 C) and nitrogen (?? 15 N) isotopes in biological samples from large herbivores identify photosynthetic pathways (C 3 vs. C 4 ) of plants they consumed and can elucidate potential nutritional characteristics of dietary selection. Because large herbivores consume a diversity of forage types, ?? 13 C and ?? 15 N in their tissue can index ingested and assimilated diets through time. We assessed ?? 13 C and ?? 15 N in metabolically active liver tissue of sympatric mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) to identify dietary disparity resulting from use of burned and unburned areas in a largely forested landscape. Interspecific variation in dietary disparity of deer was documented 2-3 years post-fire in response to lag-time effects of vegetative response to burning and seasonal (i.e., summer, winter) differences in forage type. Liver ?? 13 C for mule deer were lower during winter and higher during summer 2 years post-fire on burned habitat compared to unburned habitat suggesting different forages were consumed by mule deer in response to fire. Liver ?? 15 N for both species were higher on burned than unburned habitat during winter and summer suggesting deer consumed more nutritious forage on burned habitat during both seasons 2 and 3 years post-fire. Unlike traditional methods of dietary assessment that do not measure uptake of carbon and nitrogen from dietary components, analyses of stable isotopes in liver or similar tissue elucidated ?? 13 C and ?? 15 N assimilation from seasonal dietary components and resulting differences in the foraging ecology of sympatric species in response to fire.

Wildlife Biology in Practice↗
USGS2022

Defining biologically relevant and hierarchically nested population units to inform wildlife management

Wildlife populations are increasingly affected by natural and anthropogenic changes that negatively alter biotic and abiotic processes at multiple spatiotemporal scales and therefore require increased wildlife management and conservation efforts. However, wildlife management boundaries frequently lack biological context and mechanisms to assess demographic data across the multiple spatiotemporal scales influencing populations. To address these limitations, we developed a novel approach to define biologically relevant subpopulations of hierarchically nested population levels that could facilitate managing and conserving wildlife populations and habitats. Our approach relied on the Spatial “K”luster Analysis by Tree Edge Removal clustering algorithm, which we applied in an agglomerative manner (bottom-to-top). We modified the clustering algorithm using a workflow and population structure tiers from least-cost paths, which captured biological inferences of habitat conditions (functional connectivity), dispersal capabilities (potential connectivity), genetic information, and functional processes affecting movements. The approach uniquely included context of habitat resources (biotic and abiotic) summarized at multiple spatial scales surrounding locations with breeding site fidelity and constraint-based rules (number of sites grouped and population structure tiers). We applied our approach to greater sage-grouse ( Centrocercus urophasianus ), a species of conservation concern, across their range within the western United States. This case study produced 13 hierarchically nested population levels (akin to cluster levels, each representing a collection of subpopulations of an increasing number of breeding sites). These closely approximated population closure at finer ecological scales (smaller subpopulation extents with fewer breeding sites; cluster levels ≥2), where >92% of individual sage-grouse's time occurred within their home cluster. With available population monitoring data, our approaches can support the investigation of factors affecting population dynamics at multiple scales and assist managers with making informed, targeted, and cost-effective decisions within an adaptive management framework. Importantly, our approach provides the flexibility of including species-relevant context, thereby supporting other wildlife characterized by site fidelity.

Ecology and Evolution↗
USGS2021

Seasonal variation in resource selection by subadult golden eagles in the Great Basin Desert

Golden eagles Aquila chrysaetos are a long-lived and wide-ranging species believed to be stable or in slight decline across North America. Golden eagles have an extended subadult stage (4–5 years) that is critical to maintaining recruitment into the breeding population and population viability. Compared to adult golden eagles, the ecology of subadult golden eagles (hereafter, subadults) has received little attention. We investigated patterns of resource selection for subadults in the Great Basin Desert of the western United States during summer and winter, 2013–2019. We monitored 46 subadults with GPS transmitters and related locations (n = 99 037) with predictors hypothesized to influence seasonal patterns of space use with mixed-effects logistic regression. Subadults selected for ridges and upper slopes in summer and winter, but higher elevations in summer. Subadults showed weak selection for lower ridge density in summer, which was likely facilitated by selection for areas with greater thermal wind current potential. In contrast, subadults showed strong selection for higher ridge density in winter. Subadults selected areas further from roads in summer and closer to roads and electrical transmission lines in winter, which may be related to winter scavenging of road-killed ungulates. Resource selection functions suggested subadults selected for shrublands and woodlands in both seasons, but odds ratios revealed that during winter subadults avoided shrublands and increased selection of woodlands relative to summer. Subadults selected for areas with infrequent fires in both seasons; areas with frequent fires were avoided in summer but selected for in winter. Seasonal changes in resource selection suggested that subadults used woodlands more than expected, potentially reflecting spatial partitioning by subadults to lower-quality habitats to minimize competition with breeding adults during winter when energetic demands for thermoregulation were presumably higher and prey more limited.

Utah↗
USGS2023

Genetic mark–recapture analysis reveals large annual variation in pre-breeding sex ratio of greater sage-grouse

Sex ratio, and the extent to which it varies over time, is an important factor in the demography, management, and conservation of wildlife populations. Greater sage-grouse Centrocercus urophasianus populations in western North America are monitored using counts of males at leks in spring. Population estimates derived from lek-count data typically assume a constant, female-biased sex ratio, yet few rigorous, empirically derived estimates of sex ratio are available to test that assumption. We estimated pre-breeding sex ratio of greater sage-grouse in a peripheral, geographically isolated population in northwestern Colorado during two consecutive winters using closed-population, robust-design, multi-state, genetic mark–recapture models in program MARK. Sex ratio varied markedly between years, with estimates of 3.29 (95% CI: 2.36–4.59) females per male in winter 2012–2013 and 1.54 (95% CI: 1.22–1.95) females per male in winter 2013–2014. Rather than assuming a constant sex ratio, biologists should consider the potential for large annual variation in sex ratio of greater sage-grouse populations when estimating population size or trend from male lek-count data.

Wildlife Biology↗