Geology topics

David J. Delehanty

Publications and source records attributed to David J. Delehanty.

36 records · Page 2Linked to original sources

USGS2018

Movements of female Sage Grouse Centrocercus urophasianus during incubation recess

We combined GPS data‐loggers, VHF transmitters, and DVR video‐monitoring to measure fine‐scale movement patterns during daily incubation recesses by female Sage Grouse Centrocercus urophasianus , a species with uniparental incubation that has experienced widespread population decline and distributional contraction. Most (69.6%) Sage Grouse recess activity was highly localized within a core recess area averaging 2.58 ± 0.64 ha and females remained within 242.3 ± 30.0 m from the nest during recesses (total recess areas were 11.06 ± 2.27 ha). Visually conspicuous Sage Grouse movements near nests at the start and end of recesses and consistent occupation of core recess areas point to a mechanism for newly abundant predators such as the Northern Raven Corvus corax to detect and depredate Sage Grouse nests. Our methods apply to other avian species of scientific interest and conservation concern.

Ibis↗

USGS2018

Broad‐scale occurrence of a subsidized avian predator: reducing impacts of ravens on sage‐grouse and other sensitive prey

Expanding human enterprise across remote environments impacts numerous wildlife species. Anthropogenic resources provide subsidies for generalist predators that can lead to cascading effects on prey species at lower trophic levels. A fundamental challenge for applied ecologists is to disentangle natural and anthropogenic influences on species occurrence, and subsequently develop spatially explicit models to help inform management and conservation decisions. Using Bayesian hierarchical occupancy models, we mapped the broad‐scale occurrence of common ravens Corvus corax as a function of natural and anthropogenic landscape covariates using >15,000 point count surveys performed during 2007–2016 within the Great Basin region, USA. Raven abundance and distribution is substantially increasing across the American west due to unintended anthropogenic resource subsidies. Importantly, ravens prey on eggs and chicks of numerous species including greater sage‐grouse Centrocercus urophasianus , an indicator species whose decline is at the centre of national conservation strategies and land use policies.Anthropogenic factors that contributed to greater raven occurrence were: increased road density, presence of transmission lines, agricultural activity, and presence of roadside rest areas. Natural landscape characteristics included lower elevations with greener vegetation (NDVI), greater stream and habitat edge densities, and lower percentages of big sagebrush A. tridentata spp . Interactions between anthropogenic sources of nesting substrate and food subsidies suggested that raven occurrence increased multiplicatively when these resource subsidies co‐occurred. Overall, the average probability of raven occurrence estimated within sagebrush ecosystems of the study area was ~0.83. Synthesis and applications . We demonstrate how anthropogenic factors can be disentangled from natural effects when making spatially‐explicit predictions of subsidized predators occurring across expansive landscapes. This approach can guide management decisions where subsidized predators overlap sensitive prey habitats. For example, we identify areas where elevated raven occurrence coincides with breeding sage‐grouse concentration areas and appears to be largely driven by anthropogenic factors. Management applications could focus on reducing raven access to anthropogenic subsidies in these areas, while prioritizing habitat improvements for sage‐grouse elsewhere. Our approach is applicable to other species where widespread survey data are available.

Journal of Applied Ecology↗

USGS2018

Post-release breeding of translocated sharp-tailed grouse and an absence of artificial insemination effects

Context: Translocation has become a widely used method to restore wildlife populations following extirpation. For some species, such as lekking grouse, which breed at traditional mating grounds, reproduction is linked to culturally established geographic locations. Cultural centres are lost upon extirpation, making restoration into otherwise rehabilitated habitats especially challenging. The process by which species with culturally dependent reproduction sometimes become re-established is poorly understood and merits investigation to improve conservation strategies. Aims: We reintroduced CSTG to vacant habitat in north-central Nevada, USA, from 2013 to 2017, with concordant goals of promoting females to nest and males to lek. We tested the utility of performing artificial insemination (AI) on females before translocation and we conducted paternity analyses to understand male reproduction. Methods: We monitored females for the effects of AI on nest initiation, nest survival and egg fertility. We used post-hatch extra-embryonic membranes and other tissues to evaluate paternity of chicks produced at the restoration site. Key results: Artificial insemination had no effect on female survival or nest initiation, and did not fertilise any eggs within nine sampled clutches ( n = 102 eggs). Most paternity was attributable to male residents that had survived for ≥1 year at the restoration site before the arrival of translocated females. Conclusions: Artificial insemination neither aided nor harmed female reproduction. A small number of translocated, resident adult males sired reproduction following female release. Implications: The presence of resident males at restoration sites may be more likely to result in post-translocation reproduction than is pre-translocation AI. Restoring CSTG to vacant habitat should focus on translocating females into suitable nesting habitat while simultaneously ensuring that reproductively capable males are available within or adjacent to the nesting habitat.

Wildlife Research↗

USGS2017

Greater sage-grouse ( Centrocercus urophasianus ) nesting and brood-rearing microhabitat in Nevada and California—Spatial variation in selection and survival patterns

Greater sage-grouse ( Centrocercus urophasianus ; hereinafter, "sage-grouse") are highly dependent on sagebrush ( Artemisia spp.) dominated vegetation communities for food and cover from predators. Although this species requires the presence of sagebrush shrubs in the overstory, it also inhabits a broad geographic distribution with significant gradients in precipitation and temperature that drive variation in sagebrush ecosystem structure and concomitant shrub understory conditions. Variability in understory conditions across the species’ range may be responsible for the sometimes contradictory findings in the scientific literature describing sage-grouse habitat use and selection during important life history stages, such as nesting. To help understand the importance of this variability and to help guide management actions, we evaluated the nesting and brood-rearing microhabitat factors that influence selection and survival patterns in the Great Basin using a large dataset of microhabitat characteristics from study areas spanning northern Nevada and a portion of northeastern California from 2009 to 2016. The spatial and temporal coverage of the dataset provided a powerful opportunity to evaluate microhabitat factors important to sage-grouse reproduction, while also considering habitat variation associated with different climatic conditions and areas affected by wildfire. The summary statistics for numerous microhabitat factors, and the strength of their association with sage-grouse habitat selection and survival, are provided in this report to support decisions by land managers, policy-makers, and others with the best-available science in a timely manner.

California, Nevada↗

USGS2016

Spatially explicit modeling of annual and seasonal habitat for greater sage-grouse ( Centrocercus urophasianus ) in Nevada and Northeastern California—An updated decision-support tool for management

Successful adaptive management hinges largely upon integrating new and improved sources of information as they become available. As a timely example of this tenet, we updated a management decision support tool that was previously developed for greater sage-grouse ( Centrocercus urophasianus , hereinafter referred to as “sage-grouse”) populations in Nevada and California. Specifically, recently developed spatially explicit habitat maps derived from empirical data played a key role in the conservation of this species facing listing under the Endangered Species Act. This report provides an updated process for mapping relative habitat suitability and management categories for sage-grouse in Nevada and northeastern California (Coates and others, 2014, 2016). These updates include: (1) adding radio and GPS telemetry locations from sage-grouse monitored at multiple sites during 2014 to the original location dataset beginning in 1998; (2) integrating output from high resolution maps (1–2 m 2 ) of sagebrush and pinyon-juniper cover as covariates in resource selection models; (3) modifying the spatial extent of the analyses to match newly available vegetation layers; (4) explicit modeling of relative habitat suitability during three seasons (spring, summer, winter) that corresponded to critical life history periods for sage-grouse (breeding, brood-rearing, over-wintering); (5) accounting for differences in habitat availability between more mesic sagebrush steppe communities in the northern part of the study area and drier Great Basin sagebrush in more southerly regions by categorizing continuous region-wide surfaces of habitat suitability index (HSI) with independent locations falling within two hydrological zones; (6) integrating the three seasonal maps into a composite map of annual relative habitat suitability; (7) deriving updated land management categories based on previously determined cut-points for intersections of habitat suitability and an updated index of sage-grouse abundance and space-use (AUI); and (8) masking urban footprints and major roadways out of the final map products. Seasonal habitat maps were generated based on model-averaged resource selection functions (RSF) derived for 10 project areas (813 sage-grouse; 14,085 locations) during the spring season, 10 during the summer season (591 sage-grouse, 11,743 locations), and 7 during the winter season (288 sage-grouse, 4,862 locations). RSF surfaces were transformed to HSIs and averaged in a GIS framework for every pixel for each season. Validation analyses of categorized HSI surfaces using a suite of independent datasets resulted in an agreement of 93–97 percent for habitat versus non-habitat on an annual basis. Spring and summer maps validated similarly well at 94–97 percent, while winter maps validated slightly less accurately at 87–93 percent. We then provide an updated example of how space use models can be integrated with habitat models to help inform conservation planning. We used updated lek count data to calculate a composite abundance and space use index (AUI) that comprised the combination of probabilistic breeding density with a non-linear probability of occurrence relative to distance to nearest lek. The AUI was then classified into two categories of use (high and low-to-no) and intersected with the HSI categories to create potential management prioritization scenarios based on information about sage-grouse occupancy coupled with habitat suitability. Compared to Coates and others (2014, 2016), the amount of area classified as habitat across the region increased by 6.5 percent (approximately 1,700,000 acres). For management categories, core increased by 7.2 percent (approximately 865,000 acres), priority increased by 9.6 percent (approximately 855,000 acres), and general increased by 9.2 percent (approximately 768,000 acres), while non-habitat decreased (that is, classified non-habitat occurring outside of areas of concentrated use) by 11.9 percent (approximately 2,500,000 acres). Importantly, seasonal and annual maps represent habitat for all age and sex classes of sage-grouse (that is, sample sizes of marked grouse were insufficient to only construct models for reproductive females). This revised sage-grouse habitat mapping product helps improve adaptive application of conservation planning tools based on intersections of spatially explicit habitat suitability, abundance, and space use indices.

California, Nevada↗

USGS2016

Landscape characteristics and livestock presence influence common ravens: Relevance to greater sage-grouse conservation

Common raven ( Corvus corax ; hereafter, raven) population abundance in the sagebrush steppe of the American West has increased threefold during the previous four decades, largely as a result of unintended resource subsidies from human land-use practices. This is concerning because ravens frequently depredate nests of species of conservation concern, such as greater sage-grouse ( Centrocercus urophasianus ; hereafter, sage-grouse). Grazing by livestock in sagebrush ecosystems is common practice on most public lands, but associations between livestock and ravens are poorly understood. The primary objective of this study was to identify the effects of livestock on raven occurrence while accounting for landscape characteristics within human-altered sagebrush steppe habitat, particularly in areas occupied by breeding sage-grouse. Using data from southeastern Idaho collected during spring and summer across 3 yr, we modeled raven occurrence as a function of the presence of livestock while accounting for multiple landscape covariates, including land cover features, topographical features, and proximity to sage-grouse lek sites (breeding grounds), as well as site-level anthropogenic features. While accounting for landscape characteristics, we found that the odds of raven occurrence increased 45.8% in areas where livestock were present. In addition, ravens selected areas near sage-grouse leks, with the odds of occurrence decreasing 8.9% for every 1-km distance, increase away from the lek. We did not find an association between livestock use and distance to lek. We also found that ravens selected sites with relatively lower elevation containing increased amounts of cropland, wet meadow, and urbanization. Limiting raven access to key anthropogenic subsidies and spatially segregating livestock from sage-grouse breeding areas would likely reduce exposure of predatory ravens to sage-grouse nests and chicks.

Idaho↗

USGS2016

Survival of translocated sharp-tailed grouse: Temporal threshold and age effects

Context: The Columbian sharp-tailed grouse ( Tympanuchus phasianellus columbianus) is a subspecies of conservation concern in the western United States, currently occupying ≤10% of its historic range. Land and management agencies are employing translocation techniques to restore Columbian sharp-tailed grouse (CSTG) populations. However, establishing self-sustaining populations by translocating grouse often is unsuccessful, owing, in part, to low survivorship of translocated grouse following release. Aims: We measured and modelled patterns of CSTG mortality for 150 days following translocation into historic range, to better understand patterns and causes of success or failure in conservation efforts to re-establish grouse populations. Methods: We conducted two independent multi-year translocations and evaluated individual and temporal factors associated with CSTG survival up to 150 days following their release. Both translocations were reintroduction attempts in Nevada, USA, to establish viable populations of CSTG into their historic range. Key results: We observed a clear temporal threshold in survival probability, with CSTG mortality substantially higher during the first 50 days following release than during the subsequent 100 days. Additionally, translocated yearling grouse exhibited higher overall survival (0.669 ± 0.062) than did adults (0.420 ± 0.052) across the 150-day period and higher survival than adults both before and after the 50-day temporal threshold. Conclusions: Translocated CSTG are especially vulnerable to mortality for 50 days following release, whereas translocated yearling grouse are more resistant to mortality than are adult grouse. On the basis of the likelihood of survival, yearling CSTG are better candidates for population restoration through translocation than are adult grouse. Implications: Management actions that ameliorate mortality factors for 50 days following translocation and translocations that employ yearling grouse will increase the likelihood of population establishment.

Idaho, Nevada↗

USGS2015

Integrating spatially explicit indices of abundance and habitat quality: an applied example for greater sage-grouse management

Predictive species distributional models are a cornerstone of wildlife conservation planning. Constructing such models requires robust underpinning science that integrates formerly disparate data types to achieve effective species management. Greater sage-grouse Centrocercus urophasianus , hereafter “sage-grouse” populations are declining throughout sagebrush-steppe ecosystems in North America, particularly within the Great Basin, which heightens the need for novel management tools that maximize use of available information. Herein, we improve upon existing species distribution models by combining information about sage-grouse habitat quality, distribution, and abundance from multiple data sources. To measure habitat, we created spatially explicit maps depicting habitat selection indices (HSI) informed by > 35 500 independent telemetry locations from > 1600 sage-grouse collected over 15 years across much of the Great Basin. These indices were derived from models that accounted for selection at different spatial scales and seasons. A region-wide HSI was calculated using the HSI surfaces modelled for 12 independent subregions and then demarcated into distinct habitat quality classes. We also employed a novel index to describe landscape patterns of sage-grouse abundance and space use (AUI). The AUI is a probabilistic composite of: (i) breeding density patterns based on the spatial configuration of breeding leks and associated trends in male attendance; and (ii) year-round patterns of space use indexed by the decreasing probability of use with increasing distance to leks. The continuous AUI surface was then reclassified into two classes representing high and low/no use and abundance. Synthesis and application s. Using the example of sage-grouse, we demonstrate how the joint application of indices of habitat selection, abundance, and space use derived from multiple data sources yields a composite map that can guide effective allocation of management intensity across multiple spatial scales. As applied to sage-grouse, the composite map identifies spatially explicit management categories within sagebrush steppe that are most critical to sustaining sage-grouse populations as well as those areas where changes in land use would likely have minimal impact. Importantly, collaborative efforts among stakeholders guide which intersections of habitat selection indices and abundance and space use classes are used to define management categories. Because sage-grouse are an umbrella species, our joint-index modelling approach can help target effective conservation for other sagebrush obligate species, and can be readily applied to species in other ecosystems with similar life histories, such as central-placed breeding.

California, Nevada↗

USGS2015

Nest-site selection and reproductive success of greater sage-grouse in a fire-affected habitat of northwestern Nevada

Identifying links between micro-habitat selection and wildlife reproduction is imperative to population persistence and recovery. This information is particularly important for landscape species such as greater sage-grouse ( Centrocercus urophasianus ; sage-grouse). Although this species has been widely studied, because environmental factors can affect sage-grouse populations, local and regional studies are crucial for developing viable conservation strategies. We studied the habitat-use patterns of 71 radio-marked sage-grouse inhabiting an area affected by wildfire in the Virginia Mountains of northwestern Nevada during 2009–2011 to determine the effect of micro-habitat attributes on reproductive success. We measured standard vegetation parameters at nest and random sites using a multi-scale approach (range = 0.01–15,527 ha). We used an information-theoretic modeling approach to identify environmental factors influencing nest-site selection and survival, and determine whether nest survival was a function of resource selection. Sage-grouse selected micro-sites with greater shrub canopy cover and less cheatgrass ( Bromus tectorum ) cover than random sites. Total shrub canopy, including sagebrush ( Artemisia spp.) and other shrub species, at small spatial scales (0.8 ha and 3.1 ha) was the single contributing selection factor to higher nest survival. These results indicate that reducing the risk of wildfire to maintain important sagebrush habitats could be emphasized in sage-grouse conservation strategies in Nevada. Managers may seek to mitigate the influx of annual grass invasion by preserving large intact sagebrush-dominated stands with a mixture of other shrub species. For this area of Nevada, the results suggest that ≥40% total shrub canopy cover in sage-grouse nesting areas could yield improved reproductive success.

Nevada↗

USGS2014

Common raven occurrence in relation to energy transmission line corridors transiting human-altered sagebrush steppe

Energy-related infrastructure and other human enterprises within sagebrush steppe of the American West often results in changes that promote common raven ( Corvus corax ; hereafter, raven) populations. Ravens, a generalist predator capable of behavioral innovation, present a threat to many species of conservation concern. We evaluate the effects of detailed features of an altered landscape on the probability of raven occurrence using extensive raven survey ( n = 1045) and mapping data from southern Idaho, USA. We found nonlinear relationships between raven occurrence and distances to transmission lines, roads, and facilities. Most importantly, raven occurrence was greater with presence of transmission lines up to 2.2 km from the corridor.We further explain variation in raven occurrence along anthropogenic features based on the amount of non-native vegetation and cover type edge, such that ravens select fragmented sagebrush stands with patchy, exotic vegetative introgression. Raven occurrence also increased with greater length of edge formed by the contact of big sagebrush ( Artemisia tridentate spp.) with non-native vegetation cover types. In consideration of increasing alteration of sagebrush steppe, these findings will be useful for planning energy transmission corridor placement and other management activities where conservation of sagebrush obligate species is a priority.

Idaho↗

USGS2014

Selection of anthropogenic features and vegetation characteristics by nesting Common Ravens in the sagebrush ecosystem

Common Raven ( Corvus corax ) numbers and distribution are increasing throughout the sagebrush steppe, influencing avian communities in complex ways. Anthropogenic structures are thought to increase raven populations by providing food and nesting subsidies, which is cause for concern because ravens are important nest predators of sensitive species, including Greater Sage-Grouse ( Centrocercus urophasianus ). During 2007–2009, we located raven nests in southeastern Idaho and conducted a resource selection analysis. We measured variables at multiple spatial scales for 72 unique nest locations, including landscape-level vegetation characteristics and anthropogenic structures. Using generalized linear mixed models and an information-theoretic approach, we found a 31% decrease in the odds of nesting by ravens for every 1 km increase in distance away from a transmission line. Furthermore, a 100-m increase in distance away from the edge of two different land cover types decreased the odds of nesting by 20%, and an increase in the amount of edge by 1 km within an area of 102.1 ha centered on the nest increased the odds of nesting by 49%. A post hoc analysis revealed that ravens were most likely to nest near edges of adjoining big sagebrush ( Artemisia tridentata ) and land cover types that were associated with direct human disturbance or fire. These findings contribute to our understanding of raven expansion into rural environments and could be used to make better-informed conservation decisions, especially in the face of increasing renewable energy development.

Idaho↗

USGS2014

Landscape alterations influence differential habitat use of nesting buteos and ravens within sagebrush ecosystem: implications for transmission line development

A goal in avian ecology is to understand factors that influence differences in nesting habitat and distribution among species, especially within changing landscapes. Over the past 2 decades, humans have altered sagebrush ecosystems as a result of expansion in energy production and transmission. Our primary study objective was to identify differences in the use of landscape characteristics and natural and anthropogenic features by nesting Common Ravens ( Corvus corax ) and 3 species of buteo (Swainson's Hawk [ Buteo swainsoni ], Red-tailed Hawk [ B. jamaicensis ], and Ferruginous Hawk [ B. regalis ]) within a sagebrush ecosystem in southeastern Idaho. During 2007–2009, we measured multiple environmental factors associated with 212 nest sites using data collected remotely and in the field. We then developed multinomial models to predict nesting probabilities by each species and predictive response curves based on model-averaged estimates. We found differences among species related to nesting substrate (natural vs. anthropogenic), agriculture, native grassland, and edge (interface of 2 cover types). Most important, ravens had a higher probability of nesting on anthropogenic features (0.80) than the other 3 species (<0.10), and the probability of nesting near agriculture was greatest for ravens (0.55) followed by Swainson's Hawk (0.28). We also describe changes in nesting densities over 4 decades at this site as related to natural and anthropogenic disturbances. Since the 1970s, the composition of the raptor and raven nesting community has drastically changed with anthropogenic alterations and loss of continuous stands of sagebrush ( Artemisia spp.), favoring increased numbers of nesting ravens and fewer nesting Ferruginous Hawks. Our results indicate that habitat alterations, fragmentation, and forthcoming disturbances anticipated with continued energy development in sagebrush steppe ecosystems can lead to predictable changes in raptor and raven communities.

Idaho↗

USGS2014

Spatially explicit modeling of greater sage-grouse ( Centrocercus urophasianus ) habitat in Nevada and northeastern California: a decision-support tool for management

Greater sage-grouse ( Centrocercus urophasianus , hereafter referred to as “sage-grouse”) populations are declining throughout the sagebrush ( Artemisia spp.) ecosystem, including millions of acres of potential habitat across the West. Habitat maps derived from empirical data are needed given impending listing decisions that will affect both sage-grouse population dynamics and human land-use restrictions. This report presents the process for developing spatially explicit maps describing relative habitat suitability for sage-grouse in Nevada and northeastern California. Maps depicting habitat suitability indices (HSI) values were generated based on model-averaged resource selection functions informed by more than 31,000 independent telemetry locations from more than 1,500 radio-marked sage-grouse across 12 project areas in Nevada and northeastern California collected during a 15-year period (1998–2013). Modeled habitat covariates included land cover composition, water resources, habitat configuration, elevation, and topography, each at multiple spatial scales that were relevant to empirically observed sage-grouse movement patterns. We then present an example of how the HSI can be delineated into categories. Specifically, we demonstrate that the deviation from the mean can be used to classify habitat suitability into three categories of habitat quality (high, moderate, and low) and one non-habitat category. The classification resulted in an agreement of 93–97 percent for habitat versus non-habitat across a suite of independent validation datasets. Lastly, we provide an example of how space use models can be integrated with habitat models to help inform conservation planning. In this example, we combined probabilistic breeding density with a non-linear probability of occurrence relative to distance to nearest lek (traditional breeding ground) using count data to calculate a composite space use index (SUI). The SUI was then classified into two categories of use (high and low-to-no) and intersected with the HSI categories to create potential management prioritization scenarios based oninformation about sage-grouse occupancy coupled with habitat suitability. This provided an example of a conservation planning application that uses the intersection of the spatially-explicit HSI and empirically-based SUI to identify potential spatially explicit strategies for sage-grouse management. Importantly, the reported categories for the HSI and SUI can be reclassified relatively easily to employ alternative conservation thresholds that may be identified through decision-making processes with stake-holders, managers, and biologists. Moreover, the HSI/SUI interface map can be updated readily as new data become available.

California;Nevada↗

USGS2013

Greater sage-grouse nest predators in the Virginia Mountains of northwestern Nevada

Greater sage-grouse Centrocercus urophasianus, hereafter sage-grouse, populations have declined across their range due to the loss, degradation, and fragmentation of habitat. Habitat alterations can lead not only to vegetative changes but also to shifts in animal behavior and predator composition that may influence population vital rates, such as nest success. For example, common ravens Corvus corax are sage-grouse nest predators, and common raven abundance is positively associated with human-caused habitat alterations. Because nest success is a central component to sage-grouse population persistence, research that identifies factors influencing nest success will better inform conservation efforts. We used videography to unequivocally identify sage-grouse nest predators within the Virginia Mountains of northwestern Nevada, USA, from 2009 to 2011 and used maximum likelihood to calculate daily probability of nest survival. In the Virginia Mountains, fires, energy exploration, and other anthropogenic activities have altered historic sage-grouse habitat. We monitored 71 sage-grouse nests during the study, placing video cameras at 39 nests. Cumulative nest survival for all nests was 22.4% (95% CI, 13.0–33.4%), a survival rate that was significantly lower than other published results for sage-grouse in the Great Basin. Depredation was the primary cause for nest failure in our study (82.5%), and common ravens were the most frequent sage-grouse nest predator, accounting for 46.7% of nest depredations. We also successfully documented a suite of mammalian and reptilian species depredating sage-grouse nests, including some predators never previously confirmed in the literature to be sage-grouse nest predators (i.e., bobcats Lynx rufus and long-tailed weasels Mephitis frenata). Within the high elevation, disturbed habitat of the Virginia Mountains, low sage-grouse nest success may be limiting sage-grouse population growth. These results suggest that management actions that restore habitat in the Virginia Mountains and decrease anthropogenic subsidies of ravens will benefit sage-grouse.

Nevada↗

USGS2013

Survival of mountain quail translocated from two distinct source populations

Translocation of mountain quail (Oreortyx pictus) to restore viable populations to their former range has become a common practice. Because differences in post-release vital rates between animals from multiple source populations has not been well studied, wildlife and land managers may arbitrarily choose the source population or base the source population on immediate availability when planning translocation projects. Similarly, an understanding of the optimal proportion of individuals from different age and sex classes for translocation would benefit translocation planning. During 2006 and 2007, we captured and translocated 125 mountain quail from 2 ecologically distinct areas: 38 from southern California and 87 from southwestern Oregon. We released mountain quail in the Bennett Hills of south-central Idaho. We radio-marked and monitored a subsample of 58 quail and used them for a 2-part survival analysis. Cumulative survival probability was 0.23 ± 0.05 (SE) at 150 days post-release. We first examined an a priori hypothesis (model) that survival varied between the 2 distinct source populations. We found that source population did not explain variation in survival. This result suggests that wildlife managers have flexibility in selecting source populations for mountain quail translocation efforts. In a post hoc examination, we pooled the quail across source populations and evaluated differences in survival probabilities between sex and age classes. The most parsimonious model indicated that adult male survival was substantially less than survival rates of other mountain quail age and sex classes (i.e., interaction between sex and age). This result suggests that translocation success could benefit by translocating yearling males rather than adult males, perhaps because adult male breeding behavior results in vulnerability to predators

Journal of Wildlife Management↗

USGS2012

A modified night-netting technique for recapturing quail

Difficulties in recapturing radiomarked birds often prevent wildlife researchers from replacing transmitters and continuing to collect data over long time periods. We developed an effective, inexpensive capture technique for radiomarked mountain quail (Oreortyx pictus). Twenty-three of 25 mountain quail in south-central Idaho, USA, in 2006 and 2007 were recaptured for transmitter replacement. This technique will provide researchers with an opportunity to recapture relatively small birds, particularly those in dense vegetation, to help conduct long-term studies.

Wildlife Society Bulletin↗

USGS2011

Preliminary analysis of Greater Sage-grouse reproduction in the Virginia Mountains of northwestern Nevada

Relationships between habitat selection and population vital rates of greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse), recently designated as a candidate species under the Endangered Species Act, within the Great Basin are not well-understood. The growing development of renewable energy infrastructure within areas inhabited by sage-grouse is thought to influence predator and vegetation communities. For example, common ravens (Corvus corax), a synanthropic sage-grouse nest predator, are increasing range-wide and select transmission lines and other tall structures for nesting and perching. In the Virginia Mountains of northwestern Nevada, we collected preliminary information of space-use, habitat selection, and population vital rates during the nesting and brood-rearing period over two years on 56 sage-grouse. Additionally, videography at nest sites (n = 22) was used to identify sage-grouse nest predators. The study area is a potential site for renewable energy developments (i.e., wind and solar), and we plan to continue monitoring this population using a before-after-control-impact study design. The results reported here are preliminary and further data are required before conclusions can be drawn from this population of sage-grouse.

Nevada↗

USGS2008

Effects of environmental factors on incubation patterns of Greater Sage-Grouse

Birds in which only one sex incubates the eggs are often faced with a direct conflict between foraging to meet metabolic needs and incubation. Knowledge of environmental and ecological factors that shape life-history strategies of incubation is limited. We used continuous videography to make precise measurements of female Greater Sage-Grouse ( Centrocercus urophasianus ) incubation constancy (percentage of time spent at the nest in a 24-hour period) and recess duration. We used an information-theoretic approach to evaluate incubation patterns in relation to grouse age, timing of incubation, raven abundance, microhabitat, weather, and food availability. Overall, sage-grouse females showed an incubation constancy of 96% and a distinctive bimodal distribution of brief incubation recesses that peaked at sunset and 30 min prior to sunrise. Grouse typically returned to their nests during low light conditions. Incubation constancy of yearlings was lower than that of adults, particularly in the later stages of incubation. Yearlings spent more time away from nests later in the morning and earlier in the evening compared to adults. Video images revealed that nearly all predation events by Common Ravens ( Corvus corax ), the most frequently recorded predator at sage-grouse nests, took place during mornings and evenings after sunrise and before sunset, respectively. These were the times of the day when sage-grouse typically returned from incubation recesses. Recess duration was negatively related to raven abundance. We found evidence that incubation constancy increased with greater visual obstruction, usually from vegetation, of nests. An understanding of how incubation patterns relate to environmental factors will help managers make decisions aimed at increasing productivity through successful incubation.

The Condor↗