Globally accelerating frequency and extent of wildfire threatens the persistence of specialist wildlife species through direct loss of habitat and indirect facilitation of exotic invasive species. ...Habitat specialists may be especially prone to rapidly changing environmental conditions because their ability to adapt lags behind the rate of habitat alteration. As a result, these populations may become increasingly susceptible to ecological traps by returning to suboptimal breeding habitats that were dramatically altered by disturbance. We demonstrate a multistage modeling approach that integrates habitat selection and survival during the key nesting life‐stage of a bird species of high conservation concern, the greater sage‐grouse (Centrocercus urophasianus; hereafter, sage‐grouse). We applied these spatially explicit models to a spatiotemporally robust dataset of sage‐grouse nest locations and fates across wildfire‐altered sagebrush ecosystems of the Great Basin ecoregion, western United States. Female sage‐grouse exhibited intricate habitat selection patterns that varied across regional gradients of ecological productivity among sagebrush communities, but often selected nest sites that disproportionately resulted in nest failure. For example, 23% of nests occurred in wildfire‐affected habitats characterized by reduced sagebrush cover and greater composition of invasive annual grasses. We found survival of nests was negatively associated with wildfire‐affected areas, but positively associated with higher elevations with increased ruggedness and overall shrub cover. Strong site fidelity likely drove sage‐grouse to continue nesting in habitats degraded by wildfire. Hence, increasing frequency and extent of wildfire may contribute disproportionately to reduced reproductive success by creating ecological traps that act as population sinks. Identifying such habitat mismatches between selection and survival facilitates deeper understanding of the mechanisms driving reduced geographic niche space and population decline at broad spatiotemporal scales, while guiding management actions to areas that would be most beneficial to the species.
Wildfire frequency and severity has increased within Great Basin sagebrush ecosystems. Non‐native annual grasses invade burned areas, providing new fuels and promoting additional fire through a positive feedback cycle. Greater sage‐grouse can become “trapped” in the wildfire‐invasive grass feedback loop, due to strong breeding and nest site fidelity to areas where sagebrush cover and subsequent nest success becomes reduced following wildfire. Landscape modeling of nest site selection and nest survival suggests that long‐term losses in sagebrush and permanent transitions to annual grassland facilitate maladaptive breeding habitat selection and ecological niche loss.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Wildfire events are becoming more frequent and severe on a global scale. Rising temperatures, prolonged drought, and the presence of pyrophytic invasive grasses are contributing to the degradation of ...native vegetation communities. Within the Great Basin region of the western U.S., increasing wildfire frequency is transforming the ecosystem toward a higher degree of homogeneity, one dominated by invasive annual grasses and declining landscape productivity. Greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse) are a species of conservation concern that rely on large tracts of structurally and functionally diverse sagebrush (Artemisia spp.) communities. Using a 12-year (2008-2019) telemetry dataset, we documented immediate impacts of wildfire on demographic rates of a population of sage-grouse that were exposed to two large wildfire events (Virginia Mountains Fire Complex-2016; Long Valley Fire-2017) near the border of California and Nevada. Spatiotemporal heterogeneity in demographic rates were accounted for using a Before-After Control-Impact Paired Series (BACIPS) study design. Results revealed a 40% reduction in adult survival and a 79% reduction in nest survival within areas impacted by wildfires. Our results indicate that wildfire has strong and immediate impacts to two key life stages of a sagebrush indicator species and underscores the importance of fire suppression and immediate restoration following wildfire events.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Anthropogenic resource subsidization across western ecosystems has contributed to widespread increases in generalist avian predators, including common ravens (Corvus corax; hereafter, raven). Ravens ...are adept nest predators and can negatively impact species of conservation concern. Predation effects from ravens are especially concerning for greater sage‐grouse (Centrocercus urophasianus; hereafter, sage‐grouse), which have experienced prolonged population decline. Our objectives were to quantify spatiotemporal patterns in raven density, evaluate sage‐grouse nest success concurrent with fluctuating raven densities, and demonstrate a spatially explicit decision support tool to guide management applications to appropriate conflict areas. We combined ~28,000 raven point count surveys with data from more than 900 sage‐grouse nests between 2009 and 2019 within the Great Basin, USA. We modeled variation in raven density using a Bayesian hierarchical distance sampling approach with environmental covariates on detection and abundance. Concurrently, we modeled sage‐grouse nest survival using a hierarchical frailty model as a function of raven density and other environmental covariates that influence the risk of nest failure. Raven density commonly exceeded 0.5 ravens km−2 and increased at low elevations with more anthropogenic development and/or agriculture. Reduced sage‐grouse nest survival was strongly associated with elevated raven density (e.g., >0.5 ravens km−2) and varied with topographic ruggedness, shrub cover, and burned areas. For conservation application, we developed a spatially explicit planning tool that predicts nest survival under current and reduced raven numbers within the Great Basin to help direct management actions to localized areas where sage‐grouse nests are at highest risk of failure. Our modeling framework can be generalized to multiple species where spatially registered abundance and demographic data are available.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Unprecedented conservation efforts for sagebrush (
Artemisia
spp.) ecosystems across the western United States have been catalyzed by risks from escalated wildfire activity that reduces habitat for ...sagebrush-obligate species such as Greater Sage-Grouse (
Centrocercus urophasianus
). However, post-fire restoration is challenged by spatial variation in ecosystem processes influencing resilience to disturbance and resistance to non-native invasive species, and spatial and temporal lags between slower sagebrush recovery processes and faster demographic responses of sage-grouse to loss of important habitat. Decision-support frameworks that account for these factors can help users strategically apply restoration efforts by predicting short and long-term ecological benefits of actions. Here, we developed a framework that strategically targets burned areas for restoration actions (e.g., seeding or planting sagebrush) that have the greatest potential to positively benefit sage-grouse populations through time. Specifically, we estimated sagebrush recovery following wildfire and risk of non-native annual grass invasion under four scenarios: passive recovery, grazing exclusion, active restoration with seeding, and active restoration with seedling transplants. We then applied spatial predictions of integrated nest site selection and survival models before wildfire, immediately following wildfire, and at 30 and 50 years post-wildfire based on each restoration scenario and measured changes in habitat. Application of this framework coupled with strategic planting designs aimed at developing patches of nesting habitat may help increase operational resilience for fire-impacted sagebrush ecosystems.
Resource managers and scientists across western U.S. agencies seek methodologies for identifying environmental attributes important to both wildlife conservation and broad-scale land stewardship. The ...Greater Sage-Grouse (Centrocercus urophasianus; hereafter, sage-grouse) exemplifies a species in need of this broad-scale approach given widespread population declines that have resulted from loss and degradation of habitat from natural and anthropogenic disturbances. These include agricultural land conversion, conifer expansion, energy development, and wildfire coupled with ecological conversion by invasive plants such as cheatgrass (Bromus tectorum). Development of habitat assessments and conservation actions for sage-grouse benefit from studies that link demographic responses to habitat selection patterns. To address this, we examined nest survival of sage-grouse in relation to fine-scale habitat patterns (i.e., field-based habitat measurements) that influenced nest site selection, using data from nests of telemetered females at 17 sites over 6 years in Nevada and northeastern California, USA. Importantly, sites spanned mesic and xeric average precipitation conditions that contributed substantially to vegetation community structure across cold desert ecosystems of the North American Great Basin. Vegetative cover immediately surrounding sage-grouse nests was important for both nest site selection and nest survival, but responses varied between mesic and xeric sites. For example, while taller perennial grasses were selected at xeric sites, we found no evidence of selection for perennial grass at mesic sites, indicating a functional response to availability of habitat features between hydrographic regions. Furthermore, perennial grass height and forb height both had positive effects on nest survival at xeric sites, but we found varying effects at mesic sites. We emphasize that precipitation conditions driving ecosystem productivity vary regionally among sagebrush communities, shaping vegetation structure and suitable habitat conditions for nesting sage-grouse. How to Cite Brussee, B. E., P. S. Coates, S. T. O'Neil, M. A. Ricca, J. E. Dudko, S. P. Espinosa, S. C. Gardner, M. L. Casazza, and D. J. Delehanty (2022). Influence of fine-scale habitat characteristics on sage-grouse nest site selection and nest survival varies by mesic and xeric site conditions. Ornithological Applications 125:duac052. LAY SUMMARY Effective conservation and management for sensitive species requires maintenance of habitat conditions that promote demographic success and persistence of populations. We measured field-based fine-scale vegetation characteristics at nests of Greater Sage-Grouse across 17 sites within California and Nevada, USA, during 2012–2017, and we examined associations with nest selection and nest survival among female sage-grouse nesting in mesic and xeric sagebrush-steppe environments. We demonstrate strong associations with fine-scale features and variation in these associations across precipitation conditions. Our results suggest differences in the regional availability of important vegetation components across xeric and mesic conditions that influence sage-grouse occurrence and reproductive success and highlight the importance of ecological context and long-term average precipitation when developing habitat management prescriptions. Variation in the relative influences of herbaceous cover among habitat types within our study helps to elucidate discrepancies observed among studies of grass-related variables affecting selection or survival of sage-grouse nests. Los administradores de recursos y los científicos de las agencias del oeste de EEUU buscan metodologías para identificar atributos ambientales importantes tanto para la conservación de la vida silvestre como para la gobernanza de la tierra a gran escala. Centrocercus urophasianus es un ejemplo de una especie que necesita este enfoque a gran escala dada la disminución generalizada de la población como resultado de la pérdida y degradación del hábitat por disturbios naturales y antropogénicos. Estos incluyen la conversión de tierras agrícolas, la expansión de coníferas, el desarrollo energético y los incendios forestales, junto con la conversión ecológica por plantas invasoras como Bromus tectorum. El desarrollo de evaluaciones de hábitat y acciones de conservación para C. urophasianus se beneficia de estudios que vinculan las respuestas demográficas con los patrones de selección de hábitat. Para abordar esto, examinamos la supervivencia de los nidos de C. urophasianus en relación con patrones de hábitat a escala fina (i.e., mediciones de hábitat basadas en el campo) que influyeron en la selección del sitio de anidación, utilizando datos de nidos provenientes de hembras medidas con telemetría en 17 sitios durante 6 años en Nevada y el noreste de California, EEUU. Es importante destacar que los sitios abarcaron condiciones de precipitación promedio mésicas y xéricas que contribuyeron sustancialmente a la estructura de la comunidad de la vegetación en los ecosistemas desérticos fríos de la Gran Cuenca de América del Norte. La cobertura vegetal alrededor de los nidos de C. urophasianus fue importante tanto para la selección del sitio de anidación como para la supervivencia del nido, pero las respuestas variaron entre los sitios mésicos y xéricos. Por ejemplo, aunque se seleccionaron pastos perennes más altos en sitios xéricos, no encontramos evidencia de selección de pastos perennes en sitios mésicos, lo que indica una respuesta funcional a la disponibilidad de las características del hábitat entre regiones hidrográficas. Más aún, la altura del pasto perenne y la altura de las hierbas tuvieron efectos positivos en la supervivencia del nido en los sitios xéricos, pero encontramos efectos variables en los sitios mésicos. Enfatizamos en que las condiciones de precipitación que impulsan la productividad del ecosistema varían regionalmente entre las comunidades de artemisa, dando forma a la estructura de la vegetación y a las condiciones del hábitat adecuadas para la anidación de C. urophasianus.
•Hunter-harvested wings indicate Greater Sage-Grouse productivity (R).•Mesic habitat availability can be indicated via remotely sensed satellite imagery.•Mesic availability, annual precipitation, and ...landcover collectively drive R.•Snowpack and topography drive mesic habitat resources that support sage-grouse.•Management for drought resilient and mesic habitat should benefit sage-grouse.
Anticipating and mitigating the effects climate change will have on wildlife populations requires an improved understanding of the ways in which those populations are currently adapted to climate and how they are affected by variation in weather conditions. We used over 70,000 greater sage-grouse (Centrocercus urophasianus) wings, derived from hunter harvest in three western states, to characterize spatiotemporal variation in sage-grouse productivity throughout the North American Great Basin during 1993 – 2020. We then tested the hypothesis that previously-identified associations between precipitation and sage-grouse productivity are mediated by the availability of mesic habitats, which provide the diet resources required by broods during typical late-summer seasonal drought. We used random forest regression to model sage-grouse productivity as a function of mesic habitat availability (defined as those areas with maximum Normalized Difference Vegetation Index (NDVI) ≥0.3) during the late brood-rearing period, the more general effect of annual precipitation, and landcover composition. We also evaluated potential acute direct effects of exposure to inclement weather on sage-grouse productivity. Finally, we examined which weather and topographic variables best predict mesic habitat availability. We found the predicted positive relationship between mesic habitat availability and sage-grouse productivity, but annual precipitation explained additional variation in productivity even after accounting for mesic habitat availability. Hence, precipitation and drought may drive sage-grouse productivity via more than one mechanism acting on multiple demographic rates. Productivity was also limited by exotic annual grass invasion and conifer encroachment. Mesic habitat availability was a function of topographic relief, mean elevation, annual mean snow water equivalent, and winter temperatures, indicating that snowpack recharges the late summer mesic resources that support sage-grouse productivity. Management actions focused on maintaining and restoring mesic resources and drought resilient habitats, limiting the spread of exotic annual grasses, and reversing conifer encroachment should support future sage-grouse recruitment and help mitigate the effects of climate change.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Defining boundaries of species' habitat across broad spatial scales is often necessary for management decisions, and yet challenging for species that demonstrate differential variation in seasonal ...habitat use. Spatially explicit indices that incorporate temporal shifts in selection can help overcome such challenges, especially for species of high conservation concern. Greater sage‐grouse Centrocercus urophasianus (hereafter, sage‐grouse), a sagebrush obligate species inhabiting the American West, represents an important case study because sage‐grouse exhibit seasonal habitat patterns, populations are declining in most portions of their range and are central to contemporary national land use policies. Here, we modeled spatiotemporal selection patterns for telemetered sage‐grouse across multiple study sites (1,084 sage‐grouse; 30,690 locations) in the Great Basin. We developed broad‐scale spatially explicit habitat indices that elucidated space use patterns (spring, summer/fall, and winter) and accounted for regional climatic variation using previously published hydrographic boundaries. We then evaluated differences in selection/avoidance of each habitat characteristic between seasons and hydrographic regions. Most notably, sage‐grouse consistently selected areas dominated by sagebrush with few or no conifers but varied in type of sagebrush selected by season and region. Spatiotemporal variation was most apparent based on availability of water resources and herbaceous cover, where sage‐grouse strongly selected upland natural springs in xeric regions but selected larger wet meadows in mesic regions. Additionally, during the breeding period in spring, herbaceous cover was selected strongly in the mesic regions. Lastly, we expanded upon an existing joint–index framework by combining seasonal habitat indices with a probabilistic index of sage‐grouse abundance and space use to produce habitat maps useful for sage‐grouse management. These products can serve as conservation planning tools that help predict expected benefits of restoration activities, while highlighting areas most critical to sustaining sage‐grouse populations. Our joint–index framework can be applied to other species that exhibit seasonal shifts in habitat requirements to help better guide conservation actions.
Sage‐grouse habitat and populations are declining across their range, which has put this species at the center of national land use policies in western North America. Our study provides valuable information of seasonally important areas for sage‐grouse populations for restoration and/or protection, as well as spatially explicit indices that can be integrated into quantitative planning tools to aid decisions related to sage‐grouse population restoration. We developed these spatially explicit products for populations within Nevada and California, which comprise the majority of sage‐grouse within the Great Basin.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Managers require quantitative yet tractable tools that identify areas for restoration yielding effective benefits for targeted wildlife species and the ecosystems they inhabit. As a contemporary ...example of high national significance for conservation, the persistence of Greater Sage-grouse (Centrocercus urophasianus) in the Great Basin is compromised by strongly interacting stressors of conifer expansion, annual grass invasion, and more frequent wildfires occurring in sagebrush ecosystems. Associated restoration treatments to a sagebrush-dominated state are often costly and may yield relatively little ecological benefit to sage-grouse if implemented without estimating how Sage-grouse may respond to treatments, or do not consider underlying processes influencing sagebrush ecosystem resilience to disturbance and resistance to invasive species. Here, we describe example applications of a spatially explicit conservation planning tool (CPT) to inform prioritization of: (1) removal of conifers (i.e., pinyon-juniper); and (2) wildfire restoration aimed at improving habitat conditions for the Bi-State Distinct Population Segment of Sage-grouse along the California–Nevada state line. The CPT measures ecological benefits to sage-grouse for a given management action through a composite index comprised of resource selection functions and estimates of abundance and space use. For pinyon-juniper removal, we simulated changes in land-cover composition following the removal of sparse trees with intact understories, and ranked treatments on the basis of changes in ecological benefits per dollar-unit of cost. For wildfire restoration, we formulated a conditional model to simulate scenarios for land cover changes (e.g., sagebrush to annual grass) given estimated fire severity and underlying ecosystem processes influencing resilience to disturbance and resistance to invasion by annual grasses. For both applications, we compared CPT rankings to land cover changes along with sagebrush resistance and resilience metrics. Model results demonstrated how the CPT can be an important step in identifying management projects that yield the highest quantifiable benefit to Sage-grouse while avoiding costly misallocation of resources, and highlight the importance of considering changes in sage-grouse ecological response and factors influencing sagebrush ecosystem resilience to disturbance and resistance to invasion. This unique framework can be adopted to help inform other management questions aimed at improving habitat for other species across sagebrush and other ecosystems.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
Energy development and its associated infrastructure, including power lines, may influence wildlife population dynamics through effects on survival, reproduction, and movements of individuals. These ...infrastructure impacts may be direct or indirect, the former occurring when development acts directly as an agent of mortality (e.g., collision) and the latter when impacts occur as a by-product of other processes that are altered by infrastructure presence. Functional or numerical responses by predators to power-line corridors are indirect impacts that may suppress demographic rates for certain species, and perceived predation risk may affect animal behaviors such as habitat selection. Greater sage-grouse (Centrocercus urophasianus) are a species of conservation concern across western North America that may be affected by power lines. Previous studies, however, have not provided evidence for causal mechanisms influencing demographic rates. Our primary objective was to assess the influence of power lines on multiple sage-grouse vital rates, greater sage-grouse habitat selection, and ultimately greater sage-grouse population dynamics. We used demographic and behavioral data for greater sage-grouse collected from 2003 to 2012 in central Nevada, USA, accounting for sources of underlying environmental heterogeneity. We also concurrently monitored populations of common ravens (Corvus corax), a primary predator of sage-grouse nests and young. We focused primarily on a single 345 kV transmission line that was constructed at the beginning of our study; however, we also determined if similar patterns were associated with other nearby, preexisting power lines. We found that numerous behaviors (e.g., nest-site selection, brood-site selection) and demographic rates (e.g., nest survival, recruitment, and population growth) were affected by power lines, and that these negative effects were predominantly explained by temporal variation in the relative abundance of common ravens. Specifically, in years of high common raven abundance, avoidance of the transmission line was extended farther from the line, re-nesting propensity was reduced, and nest survival was lower near the transmission line relative to areas more distant from the transmission line. Additionally, we found that before and immediately after construction of the transmission line, habitats near the footprint of the transmission line were generally more productive (e.g., greater reproductive success and population growth) than areas farther from the transmission line. However, multiple demographic rates (i.e., pre-fledging chick survival, annual male survival, per capita recruitment, and population growth) for groups of individuals that used habitats near the transmission line declined to a greater extent than for individuals using habitats more distant in the years following construction of the transmission line. These decreases were correlated with an increase in common raven abundance. The geographical extent to which power lines negatively influence greater sage-grouse demographic processes was thus contingent on local raven abundance and behavior. In this system, we found that effects of power lines, depending on the behavior or demographic rate, extended 2.5–12.5 km, which exceeds current recommendations for the placement of structures in areas around sage-grouse leks. Nests located 12.5 km from the transmission line had 0.06 to 0.14 higher probabilities of hatching in years of average to high levels of raven abundance, relative to nests located within 1 km of the transmission line. Similarly, leks located 5 km from the transmission line had 0.02 to 0.16 higher rates of population growth (λ) in years of average to high levels of raven abundance, relative to leks located within 1 km of the transmission line. Our finding that negative impacts of the transmission line were associated with common raven abundance suggest that management actions that decouple this association between common raven abundance and power lines may reduce the negative indirect impacts of power lines on greater sage-grouse population dynamics. However, because the removal of common ravens or the use of perch deterrents on power lines has not been demonstrated to be consistently effective in reducing common raven predation rates on greater sage-grouse nests, we recommend preferential treatment to mitigation strategies that reduce the number of elevated structures placed within 10 km of critical greater sage-grouse habitat.
El desarrollo de energías, así como de su infraestructura asociada (incluyendo líneas eléctricas) puede afectar la dinámica poblacional de la vida silvestre debido a sus efectos en supervivencia, reproducción y movimiento. Estos efectos causados por la infraestructura pueden ser directos, o indirectos, los primeros, cuando la infraestructura actúa como un agente o causa de mortalidad (e.g., colisiones), y la segunda, cuando los efectos ocurren derivados de procesos que son alterados por la presencia de infraestructura. Respuestas funcionales o numéricas por depredadores a corredores de líneas eléctricas son considerados impactos indirectos que pueden reducir las tasas demográficas de ciertas especies. La percepción del riesgo de depredación puede afectar conductas tales como la selección de hábitat. El Gallo de Salvia (Centrocercus urophasianus) es una especie de preocupación para la conservación en el oeste de Norteamérica, que puede ser afectada por líneas eléctricas. Sin embargo, estudios previos no han proporcionada evidencia de los mecanismos causales que influencian las tasas demográficas. Utilizamos datos demográficos y conductuales del gallo de salvia recogidos del 2003 al 2012 en la zona centro de Nevada, USA, contemplando fuentes de heterogeneidad ambiental subyacente. Concurrentemente, monitoreamos poblaciones del cuervo común (Corvus corax), un depredador primario de nidos y jóvenes del gallo de salvia. Nos enfocamos principalmente en una línea de transmisión de 345kV que fue construida al inicio del estudio; sin embargo, también exploramos si patrones similares estaban asociados con otras líneas eléctricas cercanas. Encontramos que numerosas conductas (e.g., selección del sitio de anidación, y selección del sitio de crianza) y tasas demográficas (e.g., supervivencia del nido, reclutamiento, y crecimiento poblacional) fueron afectados por líneas eléctricas, y que estos efectos negativos fueron explicados predominantemente por variaciones temporales en la abundancia relativa del cuervo común. Específicamente, en años de alta abundancia del cuervo común, se incrementó la conducta de evitar las líneas eléctricas, la propensión a repetir un sitio de anidación se redujo, y la supervivencia en el nido se redujo en zonas cercanas a líneas eléctricas. Adicionalmente, encontramos que antes, e inmediatamente después de la construcción de la línea eléctrica, hábitats cercanos a la huella de la línea eléctricas fueron generalmente más productivos (e.g., mayor éxito reproductivo y crecimiento poblacional) en comparación con áreas alejadas de la línea de alta tensión. Sin embargo, múltiples tasas demográficas (e.g., supervivencia de juveniles, supervivencia anual de los machos, reclutamiento per cápita, y crecimiento poblacional) disminuyeron en mayor grado para grupos de individuos que utilizaron hábitats cercanos a las líneas de transmisión que para individuos que utilizaron hábitats más lejanos a las líneas de transmisión. Estas disminuciones estuvieron correlacionadas con un incremento en la abundancia del cuervo común. La extensión geográfica en que las líneas eléctricas tuvieron una influencia negativa en los procesos demográficos del gallo de salvia estuvo condicionada a la abundancia y conducta del cuervo común. En este sistema, encontramos que los efectos de las líneas eléctricas, dependiendo de la conducta o tasa demográfica, se extendieron 2.5–12.5 km, lo cual excede recomendaciones actuales para la colocación de estructuras en áreas alrededor de leks del gallo de salvia. Nidos encontrados a 12.5 km de la línea de transmisión tuvieron una probabilidad de eclosión en años de alta abundancia 0.06 a 0.14 mayor que nidos localizados a 1 km de la línea de transmisión. De manera similar, leks localizados a 5 km de la línea de transmisión, en años de alta abundancia de cuervos, tuvieron tasas de crecimiento poblacional (λ) 0.02 a 0.16 mayores que leks localizados a 1 km de la línea de transmisión. Nuestro descubrimiento de que los impactos negativos de las líneas de transmisión estaban asociados con la abundancia de cuervos, sugieren que las acciones de manejo que separen ésta asociación entre la abundancia del cuervo común y las líneas de transmisión pueden reducir los impactos negativos de las líneas eléctricas sobre la dinámica poblacional del gallo de salvia. Sin embargo, debido a que no se ha demostrado consistentemente la efectividad de la remoción de cuervos o el uso de disuasivos de percha de aves en las líneas de transmisión en la reducción de la depredación por cuervos en el gallo de salvia, recomendamos un tratamiento preferencial alas estrategias de mitigación que reduzcan el número de estructuras elevadas colocadas en un radio de 10 km de hábitat crítico del gallo de salvia.
Le développement énergétique et les infrastructures associées, dont les lignes électriques, peuvent influencer les dynamiques de la vie sauvage par des effets sur la survie, la reproduction et les mouvements des individus. Ces impacts des infrastructures peuvent être directs ou indirects, ce premier ayant lieu quand le développement agit directement comme agent de mortalité (par exemple par collisions) et ce dernier quand les impacts sont le produit secondaire de l’altération d’autres processus par la présence d’infrastructures. Les réponses fonctionnelles et numériques des prédateurs aux couloirs de lignes électriques sont des impacts indirects qui pourraient écraser les taux démographiq
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Translocations of North American prairie-grouse (genus Tympanuchus) present a conservation paradox wherein they are performed to augment, restore, or reintroduce populations, but translocated ...individuals exhibit a diminished ability to contribute to population restoration. For reintroduced populations without immigration, persistence can only be achieved through reproductive contributions by translocated individuals and their progeny. Due to the disruptive nature of translocation (e.g., physiological chronic stress), progeny produced at restoration sites may outperform founder populations in terms of demographics, but this hypothesis has yet to be tested. We reintroduced Columbian Sharp-tailed Grouse (T. phasianellus columbianus; CSTG) to north central Nevada from 2013 to 2017 and used integrated population models (IPMs) to evaluate the process of population establishment and estimate latent contributions of progeny hatched at the restoration site to population rate of change (). Specifically, we used annual lek (i.e. communal breeding arenas) counts and demographic data from translocated individuals to build two separate IPMs to estimate . While keeping demographic contributions by translocated individuals identical between models, one IPM assumed local progeny performance was demographically similar to translocated individuals (i.e. the baseline-IPM), and the second assumed that local progeny performed demographically similar to non-translocated CSTG (i.e. the informative-IPM). The baseline-IPM predicted strong population declines following the conclusion of translocations and extirpation by 2020, and it failed to predict observed lek counts. Conversely, the informative-IPM predicted population growth rates ( = 1.17, 95% credible interval CI: 0.74–1.50) that were more similar to field observations. Offspring of translocated individuals likely perform at similar levels to non-translocated populations, and by not accounting for demographic differences between translocated individuals and non-translocated progeny hatched at the restoration site, managers could underestimate population performance and persistence. Thus, translocation practices that maximize the number of offspring immediately recruited into restoration sites are likely to be the most successful. LAY SUMMARY Translocations of species of North American prairie-grouse (genus Tympanuchus) and sage-grouse (genus Centrocercus) often fail because translocated individuals experience high mortality and depressed reproduction. We translocated 215 Columbian Sharp-tailed Grouse (Tympanuchus phasianellus columbianus) as a species reintroduction project to Nevada, 2013–2017. Integrated population models (IPMs) derived solely from estimated demographic vital rates of translocated individuals fail to predict population growth and can erroneously predict population failure. Accurate predictions of population growth were achieved by modeling the non-monitored offspring cohort (of translocated individuals), hatched and reared at the restoration site using source population demographic rates. While translocated individuals exhibit diminished demographic vital rates, their offspring appear to mirror source populations. Offspring of translocated individuals constituted the core of the restored population. By maximizing the cohort of native offspring, managers can improve sage- and prairie-grouse translocation projects. We provide evidence for the process by which population restoration occurs in successful reintroduction projects.
PDF
