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Novel landscape elements within natural gas fields increase densities but not fitness of an important songbird nest predator

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... Nest predation was the primary source of nest mortality (over 90% of nest failures), and the deer mouse (Peromyscus maniculatus) was the most common predator observed depredating nests, accounting for 54% of 50 Brewer's Sparrow and 29% of 38 of Sage Thrasher depredations captured on video during 2011-2019 (Hethcoat and Chalfoun 2015b, A. D. Chalfoun personal observation). Deer mice were particularly attracted to the re-seeded areas surrounding well pads and along pipelines, which simultaneously provided food subsidies and cover (Sanders and Chalfoun 2018), and increased mouse abundance was correlated with increased rates of nest predation (Hethcoat and Chalfoun 2015b). Many other species depredate sagebrush songbird nests, however, including least chipmunks (Tamias minimus), thirteen-lined ground squirrels (Ictidomys tridecemlineatus), Wyoming ground squirrels (Urocitellus elegans), American badgers (Taxidea taxis), Loggerhead Shrikes (Lanius ludovicianus), corvids, and raptors (Hethcoat and Chalfoun 2015b, A. D. Chalfoun personal observation), creating the potential for nest predation in this system to operate in either an additive or compensatory manner. ...
... Plots were paired and separated by ≥650 m within pairs and ≥800 m among pairs to limit deer mouse movement between plots and pairs and ensure spatial independence. These distances were informed by the extent of mouse movements documented by powder tracking experiments during a previous, nearby study (Sanders and Chalfoun 2018). We randomly selected one plot within each pair to comprise the deer mouse removal plot, with the other serving as a reference. ...
... Specifically, we used 49 trap locations arranged in a 7 × 7 array with 40-m spacing between traps. The spacing for our reference plot trapping grids was informed by previous small mammal trapping and abundance estimation within the same study area (Sanders and Chalfoun 2018). We used Sherman live traps, baited with a mixture of peanut butter and oats at all trapping grids. ...
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Predator removal comprises one management strategy to increase the reproductive success of a prey species of concern, particularly within human-altered landscapes. The efficacy of such an approach, however, depends partly on the extent to which predation risk is additive or compensatory, which remains unknown for many systems. We experimentally reduced the local abundance of deer mice (Peromyscus maniculatus), a primary nest predator of three sagebrush-obligate songbirds—Brewer’s Sparrow (Spizella breweri), Sagebrush Sparrow (Artemisiospiza nevadensis), and Sage Thrasher (Oreoscoptus montanus)—during May to August 2019 in western Wyoming, USA, to assess whether nest predation risk was additive or compensatory, and whether nest predator removal could comprise a potentially effective management tool. Deer mouse removal did not affect the daily nest survival of songbirds between experimental and control plots, despite a reduction of 68%–85% in deer mouse abundance within treatment areas. Therefore, nest predation in this system likely operated in a compensatory way, in which deer mice that escaped removal, new immigrants, or other species of nest predator maintained similar levels of nest predation risk regardless of the prevalence of a primary predator. We caution that predator removal may not be an effective management tool in systems that lack barriers to predator immigration or have several alternative species of predators, even when a single species typically is responsible for the majority of predation events.
... The bird species with the greatest number of tests was the great-er sage-grouse (Centrocercus urophasianus) with 52 tests X(N = 11 studies), followed by the chestnut-collared longspur (Calcarius ornatus), with 51 tests from eight studies. Of the mammal papers, the majority focused on ungulates (N = 32 tests from 14 studies), with three on medium-sized mammals (small canids and mustelids) [17][18][19], two on the deer mouse [17,20], one on least chipmunks (Tamias minimus) [21], one on pygmy rabbits (Brachylagus idahoensis) [22•], and one on a large carnivore (grizzly bear, Ursus arctos) [23]. The two mammalian species that received the most study were pronghorn (Antilocapra americana; N = 19 tests from six studies) and mule deer (Odocoileus hemionus; N = 13 tests from eight studies). ...
... Understanding the processes underlying observed patterns holds particular value for formulating effective mitigation measures. As a case study, sagebrush songbirds nesting within natural gas fields experienced higher nest predation rates, which was associated with increased densities of synanthropic rodents attracted to the reseeded areas around well pads and pipelines [17,20,21]. Reproductive success of songbirds would therefore likely benefit from the reduction of initially disturbed soils and/or reclamation practices that more closely mimic initial conditions. ...
... Negative responses, however, were universally detected (albeit with relatively low frequency) across taxa, locations, and development type, and with respect to different response types and development indices (Fig. 1). Moreover, positive responses to development by some species can have negative downstream consequences for other species, such as the case of increased rodent abundance and the nest predation rates of sagebrush songbirds [17,20,21]. ...
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Purpose of Review Anthropogenic activities can lead to the loss, fragmentation, and alteration of wildlife habitats. I reviewed the recent literature (2014–2019) focused on the responses of avian, mammalian, and herpetofaunal species to oil and natural gas development, a widespread and still-expanding land use worldwide. My primary goals were to identify any generalities in species’ responses to development and summarize remaining gaps in knowledge. To do so, I evaluated the directionality of a wide variety of responses in relation to taxon, location, development type, development metric, habitat type, and spatiotemporal aspects. Recent Findings Studies ( n = 70) were restricted to the USA and Canada, and taxonomically biased towards birds and mammals. Longer studies, but not those incorporating multiple spatial scales, were more likely to detect significant responses. Negative responses of all types were present in relatively low frequencies across all taxa, locations, development types, and development metrics but were context-dependent. The directionality of responses by the same species often varied across studies or development metrics. Summary The state of knowledge about wildlife responses to oil and natural gas development has developed considerably, though many biases and gaps remain. Studies outside of North America and that focus on herpetofauna are lacking. Tests of mechanistic hypotheses for effects, long-term studies, assessment of response thresholds, and experimental designs that isolate the effects of different stimuli associated with development, remain critical. Moreover, tests of the efficacy of habitat mitigation efforts have been rare. Finally, investigations of the demographic effects of development across the full annual cycle were absent for non-game species and are critical for the estimation of population-level effects.
... We defined surface disturbance as any area that had been converted from sagebrush habitat as a result of development activities, including roads, pipelines, well pads, and reclaimed areas (in which mature sagebrush habitat had been removed during well, road, or pipeline construction and re-seeded). Whereas areas where habitat has been disturbed by energy development activities may represent habitat loss for sagebrushobligate songbirds (which breed and forage exclusively in the shrub layer), these areas represent altered, but still useable habitat for rodents (Sanders and Chalfoun 2018). ...
... Indeed, habitat modifications that lead to increased edge habitat and food resources, such as urbanization, agriculture, and energy development, tend to have the most positive effects on synanthropic species, such as deer mice and ground squirrels (Eagan et al. 2011). See Sanders and Chalfoun (2018) for further investigation into this potential mechanism. Because we could not estimate emigration and immigration rates for deer mice, our estimates of apparent survival could be confounded (Williams et al. 2002). ...
... Given our results, apex predators living near energy development do not need to be controlled to protect declining songbird populations (sensu Dinkins et al. 2016)-rather, apex predators may actually be helping to regulate rodents on natural gas fields. Moreover, our elimination of the mesopredator release hypothesis is important for strong inference and clears a path for the assessment of alternate explanations for observed patterns in mesopredator density and altered species interactions with energy extraction (Sanders and Chalfoun 2018). Effective strategies for the mitigation of negative effects of human-induced habitat change on species of concern rely on such mechanistic understanding. ...
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Anthropogenic activities are changing landscapes and the context in which predator–prey dynamics evolved, thereby altering key ecological processes and community structure. Yet, the specific mechanisms underlying such changes are rarely understood. We tested whether a mesopredator release explained increased rodent density and concomitant predation of songbird nests near natural gas development. From 2015 to 2016, we surveyed apex predators (coyotes, badgers, raptors, and corvids) and measured apparent survival and perceived predation risk of deer mice (Peromyscus maniculatus; a primary nest predator), at 12 plots spanning a gradient of surface disturbance caused by energy development in Wyoming, USA. Additionally, we measured densities of three nest predators: deer mice, least chipmunks (Tamias minimus), and thirteen‐lined ground squirrels (Ictidomys tridecemlineatus). Contrary to the mesopredator release hypothesis, counts of apex predators and perceived predation risk of deer mice increased with surface disturbance from energy development, whereas apparent survival of mice decreased. Densities of mice and ground squirrels, however, increased with surface disturbance, despite increased predation pressure. We therefore rejected the mesopredator release hypothesis as a potential mechanism underlying altered trophic dynamics near energy development. Our results suggest that apex predator control measures would not benefit declining songbirds on natural gas fields. Rather, apex predator abundance may be regulated from the bottom‐up by rodents in this system. Our results corroborate a pattern showing weakened effects of mesopredator release in habitats modified by humans. Understanding how predator–prey dynamics may be altered in novel environments requires an understanding of how predators and prey alike respond to habitat change under different contexts.
... Plots were paired and separated by ≥ 650 m within pairs and ≥ 800 m among pairs to limit deer mouse movement between plots and pairs and ensure spatial independence. These distances were informed by the extent of movements documented by powder tracking experiments of deer mice during a previous, nearby study (Sanders and Chalfoun 2018). One plot within each pair was randomly selected as the experimental plot, with the other serving as a reference. ...
... In the three reference plots, trapping 8 grids consisted of 49 trap locations arranged in a 7 x 7 array with 40 meter spacing between traps. The spacing for our reference plot trapping grids were informed by previous research in the study area (Sanders and Chalfoun 2018) and were sufficient to evaluate the density of deer mice within a plot. Both trapping grids consisted of Sherman live traps, baited with a mixture of peanut butter and oats. ...
Thesis
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Many species of wildlife go through portions of their life history where they are especially vulnerable to the impacts of biotic factors, such as predation, or numerous abiotic factors, such as weather events. The early life history of many bird species is characterized by a particularly vulnerable life stage in which they are immobile and bound to their nest location. Any selective pressures occurring during this period modulate avian biology to a large extent. We used a multifaceted approach (i.e., a controlled field experiment and an empirical study) in Wyoming, USA to address the following questions related to sagebrush songbird (Brewer’s Sparrow, Sagebrush Sparrow, Sage Thrasher) reproductive success: Chapter 1) Does nest predation by a synanthropic nest predator constitute additive or compensatory nest mortality? Chapter 2) How does an important phenotypic metric (mass) vary among nestlings in larger brood sizes and among three songbird species? We found little evidence that nest predation by deer mice on songbird nests operated in an additive manner. The year in which we conducted our experimental removal, however, had very high rates of nest survival. In our second study, intrabrood mass variation between the largest and smallest siblings of a brood differed by species (Brewer’s sparrow, Vesper Sparrow, Sage Thrasher) but was overall more extreme in larger broods. How size differences among siblings specifically manifested, however, differed by species. Our findings help characterize the survival pressures nestlings experience early in life and provide additional information regarding this critical life stage.
... The specific mechanisms that drive impacts of energy development (i.e., increased predation risk) on songbird nest survival are not well understood (but see Sanders and Chalfoun 2019). Impacts of energy development on songbird nest survival have been attributed to the physical footprint (hereafter footprint) of development (native habitat removal, fragmentation, and anthropogenic edge; Hethcoat and Chalfoun 2015a, Bernath-Plaisted and Koper 2016, Sanders and Chalfoun 2018 and to specific energy infrastructure features such as power lines (DeGregorio et al. 2014). ...
... Within these scales we used zonal statistics to calculate vegetation covariates including mean Normalized Difference Vegetation Index (NDVI), mean forb and grass understory cover, percent big sagebrush canopy cover, average sagebrush height (cm), and the standard deviation of sagebrush height (Table 1; Xian et al. 2015, Robinson et al. 2017, Jones et al. 2018, Yang et al. 2018. NDVI is as a measure of primary productivity (Robinson et al. 2017 Greater grass and forb cover and higher NDVI values can be positively associated with the abundance of deer mice (Peromyscus maniculatus), which are known to depredate Brewer's Sparrow nests (Hanser et al. 2011, Heathcoat and Chalfoun 2015a, Sanders and Chalfoun 2018. We used 30-m resolution NDVI products generated every 16 days (Robinson et al. 2017) to calculate Mean NDVI layers. ...
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Songbird communities that rely on sagebrush habitat for breeding are experiencing steep population declines, while a large amount of the sagebrush ecosystem continues to be impacted by energy development. Reclamation is increasingly emphasized as a means of mitigating impacts on species that have been affected by oil and gas development; however, the response of sagebrush species to reclamation has largely been untested. We used nest survival of the Brewer's Sparrow (Spizella breweri breweri) as an indicator of fitness responses to short-term reclamation in sagebrush habitat. We assessed oil and gas reclamation ~5 years after reclamation, but sagebrush reestablishment is a slow process; thus, the legacy of these disturbances (i.e., disturbance scars) will likely remain for decades. We compared Brewer's Sparrow nest survival across a gradient of oil and gas development from undisturbed and active development to areas that had undergone oil and gas reclamation. Nest survival was assessed at multiple scales from microhabitat to landscape. The distribution of nest sites in the active and reclamation areas suggested local avoidance of disturbance, both active and reclamation disturbance, when establishing nesting territories. We found that reclamation benefited nest survival at a local-scale when disturbance exposure exceeded 15%. Our findings demonstrated scale-dependent nest survival relationships. Across microhabitat and landscape scales, sagebrush canopy cover and composition were important to Brewer's Sparrow nest survival. Combined, these finding emphasize the importance of avoiding the removal of sagebrush habitat whenever possible and expediting sagebrush reestablishment in reclamation areas to maintain high quality sagebrush habitat for breeding songbird populations.
... Negative impacts for habitat generalists along with specialists suggests negative energy development impacts extend beyond specialists to species typically more tolerant of other forms of human development (e.g., agricultural or urban), which provide ornamental fruit-bearing trees and shrubs and other supplemental food resources (Evans et al., 2009). Non-native grasses planted for reclamation of well pad sites can promote deer mice (Peromyscus maniculatus), which may elevate nest predation pressure for birds in general (Sanders & Chalfoun, 2018). The BLM requires native seed mixes for reclamation, which occurs both after well activation in disturbed areas not required for production and after well retirement, but non-native grasses can become established, especially on private lands. ...
Article
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Estimated population trends can identify declining species to focus biologicalconservation, but monitoring may fail to illuminate causes of populationchange and strategies for reversing declines. Monitoring programs can relatetrends with environmental attributes to test causal hypotheses, but typical ana-lytical approaches do not explicitly support causal inference, diluting availabledata for informing conservation. The U.S. Bureau of Land Management(BLM) extended Integrated Monitoring in Bird Conservation Regions with aquasi-experimental sampling design over a 10-year period (2010–2019) to eval-uate the impacts of oil and gas development on sagebrush birds within theAtlantic Rim Natural Gas Field Development Project in southern Wyoming.We analyzed resulting data using a multiscale community occupancy model toestimate trends in species occupancy and richness relevant to managementtriggers. Additionally, we employed path analysis to evaluate mechanismsunderlying observed trends to inform potential management responses.Fine-scale occupancy for sage thrasher (Oreoscoptes montanus) declined withinthe high-development stratum at a rate sufficient to meet an a priori manage-ment trigger established by the BLM. Two additional sagebrush-associatedspecies, Brewer’s(Spizella breweri) and sagebrush sparrow (Artemisiospizanevadensis), exhibited negative development relationships with trend, as didoverall species richness, and richness of grassland, sagebrush, and generalistguilds. We identified well pad density and invasive plants associated withenergy development as causal factors contributing to these negative develop-ment impacts. We demonstrate an analytical approach for both estimatingoccupancy trends and identifying underlying causes to inform conservationaction. Reducing the development footprint, including well pad density andassociated invasive plants, could help reduce or limit impacts on birds withinthis landscape.
... The success of restoring or protecting habitat is dependent on whether species will use and persist in such habitat. At the patch scale, characteristics such as habitat composition, structure and quality are known to influence species occurrence and fitness parameters in a variety of taxa (Street et al. 2016;Gardiner et al. 2018;Sanders and Chalfoun 2018;Rios et al. 2021). At the landscape scale, the availability of resources such as the area of habitat available (e.g., available forest cover) and distance to high value resources (e.g., water) are important to ensure species can recolonise new areas and persist when extreme events such as drought or bushfires occur (Bjørneraas et al. 2012;Lesmerises et al. 2012). ...
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Given the high proportion of Earth’s ecosystems already anthropogenically modified, especially through clearing, it is critical we determine whether species can persist outside of their primary habitat as a means of ensuring population persistence in the remaining landscape. The koala (Phascolarctos cinereus) has been heavily impacted by habitat loss through clearing, and recently upgraded to endangered across its eastern distribution. It is timely to understand what variables may influence the occurrence of koalas in secondary habitat, which can then guide conservation efforts. We surveyed 959 sites with detection dogs to determine the occurrence of koalas through the presence of scats. Using GLMMs, we accounted for environmental and anthropogenic variables that may influence koala occurrence, meanwhile focusing on the use of secondary eucalyptus forests at multiple spatial scales (250, 500, 1500 m radii). Overall koala occurrence was negatively associated with secondary eucalyptus forests compared to primary forests, while there was no effect of total forest area present at any scale. However, we found interactive effects between secondary forest and (1) distance from the closest major road at the smallest landscape scale (250 m radii) and (2) water area at the larger landscape scales (500 m, 1500 m radii). This suggests that occurrence of koalas in secondary forests are predicted to increase when the distance to major roads, and the water area, increase. While protecting primary eucalyptus forests should always be a prioritisation for the conservation of koalas, our results emphasize the important role that secondary eucalyptus forests can play in conservation, as long as these are carefully considered in the landscape context to maximise restoration investments.
... Altered species' abundance can in turn affect interactions such as predation or competition with important fitness consequences (Faeth et al., 2005). In North America's sagebrush steppe, habitat loss and disturbance associated with energy development have been linked to the increased abundance of rodent species that are the primary nest predators of declining sagebrush-obligate songbirds (Hethcoat & Chalfoun, 2015a, 2015bSanders & Chalfoun, 2018). Nest survival of sagebrush-obligate songbirds generally decreased with surface disturbance (Hethcoat & Chalfoun, 2015a). ...
Article
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Accurate evaluations of habitat preference are key to understanding optimal conditions for wildlife survival and reproduction. Habitat selection, however, usually is evaluated using a single index of preference, and congruence among multiple, relevant indices of preference is examined rarely. We assessed the concordance between patterns of habitat preference using three different indices of breeding site preference in a migratory songbird. Specifically, we compared the chronology of territorial establishment, pair formation and reproductive initiation of the Brewer's sparrow (Spizella breweri) along a gradient of surface disturbance associated with natural gas development in Wyoming, USA during 2019. We expected all three indices to demonstrate a preference for breeding sites with less surface disturbance, where reproductive success typically is higher. By contrast, all indices suggested suboptimal preference with respect to surface disturbance, with some discrepancy among them. The chronology of settlement and pairing did not vary across the disturbance gradient, whereas nest initiation tended to occur earlier at sites with more disturbance. If the pattern of suboptimal selection of breeding sites that we identified is generalizable across other populations of migratory birds affected by energy development, the resultant lower fitness in those areas may exacerbate population declines. Our results suggest that traditional, single‐index approaches to the study of habitat selection, if chosen carefully, may provide adequate inference on habitat preferences. Different metrics, however, can lead to at least subtle differences in patterns of habitat selection. The simultaneous examination of multiple indices of preference across a diversity of systems would help clarify the contexts under which preference metrics can become decoupled.
... In contrast to human-sensitive species, some animals and plants are more resilient to human activity and even benefit from food subsidies and infrastructure associated with UOGD (e.g., nesting and roosting sites for ravens; Bui et al. 2010). Increased abundance of these species can further diminish populations of human-sensitive species through higher rates of predation (Hethcoat andChalfoun 2015, Sanders andChalfoun 2018). Similarly, invasive plants can thrive (and are sometimes actively introduced) following the soil and vegetation disturbance associated with UOGD (Bergquist et al. 2007). ...
Article
With growing evidence of widespread health and environmental impacts from oil and gas activity, localities and states are beginning to develop protective measures. Interdisciplinary approaches that integrate across human, wildlife, domesticated animal, and land health are likely to provide more just and comprehensive solutions than would be possible with siloed approaches. However, this is not common practice, and there is little guidance on how to apply such a strategy. In the present article, we summarize the state of knowledge on the impacts of terrestrial unconventional oil and gas development from the fields of ecology and public health. We then discuss synergies and trade-offs regarding impacts and mitigation strategies emerging from these two literatures. Finally, we provide recommendations for research and practice to fill knowledge gaps and better inform integrated decision-making to achieve multiple benefits and minimize impacts on human, wildlife, domesticated animals, and land health from energy development.
... Simultaneously, sagebrush habitats also have been highly converted and altered by many human activities (Knick et al. 2003), which has been associated with declines in sagebrush-obligate songbirds: Brewer's Sparrow (Spizella breweri), Sagebrush Sparrow (Artemisiospiza nevadensis), and Sage Thrasher (Oreoscoptes montanus) (Sauer et al. 2017). Mechanistic investigations of the effects of habitat change on sagebrush songbirds have revealed linkages between rates of nest predation and surface disturbance associated with energy development (Hethcoat and Chalfoun 2015a, b;Sanders and Chalfoun 2018). Sagebrush songbirds, therefore, provided an ideal system with which to simultaneously assess nest-site selection in relation to temperature variability and the risk of nest predation in situ, via the use of surface disturbance as a proxy for predation risk. ...
Article
Understanding species’ responses to temperature via behavior, and the factors affecting the extent of behavioral responses, is a critical and timely endeavor given the rapid pace at which the climate is changing. The young of altricial songbirds are particularly sensitive to temperature, and parents may modulate temperatures at nests via selection of nest sites, albeit to a largely unknown extent. We examined whether sagebrush-obligate songbirds, that reproduce within an open ecosystem with wide temperature fluctuations and span a range of body sizes, selected their nest sites on the basis of temperature. We further investigated whether nest predation risk and ambient conditions modulated temperature-based choices. We placed temperature loggers at nest sites and in unused but available nest niches and nest shrubs along a known predation-risk gradient and used nearby weather stations to determine ambient temperatures. The two smaller-bodied birds, Brewer’s Sparrow (Spizella breweri) and Sagebrush Sparrow (Artemisiospiza nevadensis), selected nest shrubs and niches that were warmer and less variable relative to unused sites whereas the larger bodied species, Sage Thrashers (Oreoscoptes montanus), did not. Brewer’s Sparrows and Sage Thrashers dampened selection for warmer nest sites when temperatures experienced during the nest-site prospecting period were warmer. None of the three species altered nest-site selection with respect to temperature in response to ambient temperature variability or our index of nest predation risk. The microhabitat characteristics that most influenced temperatures at nests varied across species. Our results suggest that songbirds can modulate temperatures at nests to some extent, and such responses can vary depending on the conditions experienced prior to nest initiation. Responses also varied across species, likely reflecting different physiological tolerances. The extent to which breeding birds will be able to continue to proximately influence temperature via nest-site choices likely will depend on the extent and rate of future climatic shifts.
... Energy development areas have the potential to become equal preference ecological traps for species in the sagebrush ecosystem (Hethcoat and Chalfoun, 2015a). Specifically, increased densities of Brewer's sparrow, vesper sparrow, and western meadowlark nest predators (e.g., rodents, corvids, American badgers; Taxidea taxus) are associated with energy development areas in many grassland and shrubland ecosystems (Grant et al., 2006, Davis and Lanyon, 2008, Coates et al., 2014, Hethcoat and Chalfoun, 2015b, Ludlow et al., 2015, Bernath-Plaisted et al., 2017, Sanders and Chalfoun, 2018. For example, vesper sparrow nest density increased with proximity to infrastructure, leading to decreased nest success, likely due to an increase in nest predators near development areas (Bernath-Plaisted and Koper, 2016). ...
Article
Reclamation projects encompassing more than several square kilometers (hereafter; landscape-scale) are a recommended strategy to mitigate the impacts of energy development on wildlife. However, the response of wildlife to landscape-scale reclamation remains largely undocumented. Oil and gas developments have contributed substantially to the loss and degradation of sagebrush ecosystems in North America. Management agencies are prioritizing habitat reclamation to mitigate habitat loss with an assumed benefit to wildlife, including songbirds. To determine the influence of landscape-scale habitat reclamation on songbirds, we measured avian species abundance and community composition in sagebrush habitats across a gradient of energy development: 1) active oil and gas, 2) landscape-scale reclamation, and 3) undisturbed sagebrush, in northeastern Wyoming, USA (2016–2018). We modeled the influence of treatment (active, reclaimed, and control), and key habitat variables on songbird abundance using a Bayesian hierarchical approach. We also assessed differences in community composition across treatments using the rarity-weighted richness estimate and the Jaccard Similarity Index. Reclamation efforts had a measurable influence on some species abundance. Human-commensal species increased in abundance with increasing disturbance, which may have increased species richness and rarity in our active and reclaimed sites. The community composition in reclaimed areas more closely resembled undeveloped habitat (control), than active development areas. Terrain roughness was the most consistently influential variable on abundance, and we recommend that this often overlooked habitat variable be included in future studies. The habitat variables that represent where we can most easily target reclamation efforts (e.g., herbaceous cover) had minimal influence on abundance.
Chapter
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Songbirds that occur across the diverse types of North American rangelands constitute many families within the Order Passeriformes, and hundreds of species. Most are declining, and many are considered potential indicator species for rangeland ecosystems. We synthesized information on the natural and life history, habitat requirements, conservation status, and responses to management of songbirds associated with North American grasslands and sagebrush steppe, two of the most geographically extensive types of rangelands. We provide a more targeted examination of the habitat associations and management considerations for two focal species, the grassland-obligate grasshopper sparrow ( Ammodramus savannarum ) and sagebrush-obligate Brewer’s sparrow ( Spizella breweri ). Grassland- and sagebrush-obligate species rely on expansive stands of grasslands and sagebrush, respectively, and we discuss how key ecological processes and rangeland management approaches—grazing, fire, and mechanical treatments—influence rangeland songbirds. Rangeland management practices can affect breeding songbirds considerably, primarily through the resultant structure and composition of vegetation, which influences the availability of preferred nesting substrates, refugia from predators, and foraging success. Optimal management strategies to limit negative consequences to rangeland songbirds will depend on the target species and local topoedaphic and climatic conditions. The maintenance of large, contiguous patches of native habitats and restoration of previously degraded areas will help facilitate the population persistence of rangeland-associated songbirds. Maintaining structural heterogeneity of habitats within landscapes, moreover, can facilitate local species diversity. Information pertaining to periods outside of the nesting stage is severely lacking for most species, which is concerning because effective management necessitates understanding of threats and limiting factors across the full annual life cycle. Moreover, information on disease effects and prevalence, the effects of a changing climate, and how both may interact with management strategies, also comprise key gaps in knowledge.
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Adaptive management and monitoring efforts focused on vegetation, habitat, and wildlife in the sagebrush (Artemisia spp.) biome help inform management of species and habitats, predict ecological responses to conservation practices, and adapt management to improve conservation outcomes. This chapter emphasizes the adaptive resource management framework with its four stages: (1) problem definition, (2) outcomes, (3) decision analysis, and (4) implementation and monitoring. Adaptive resource management is an evolving process involving a sequential cycle of learning (the accumulation of understanding over time) and adaptation (the adjustment of management over time). This framework operationalizes monitoring a necessary component of decision making in the sagebrush biome. Several national and regional monitoring efforts are underway across the sagebrush biome for both vegetation and wildlife. Sustaining these efforts and using the information effectively is an important step towards realizing the full potential of the adaptive management framework in sagebrush ecosystems. Furthermore, coordinating monitoring efforts and information across stakeholders (for example, Federal, State, nongovernmental organizations) will be necessary given the limited resources, diverse ownership/management, and sagebrush biome size.
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Spatial aspects of wildlife responses to human-induced habitat change have been examined frequently, yet the temporal dynamics of responses remain less understood. We tested alternative hypotheses for how the abundance of a suite of declining songbirds in relation to energy development changed over time. We conducted point counts at two natural gas fields during two periods spanning a decade (2008–2009 and 2018–2019), and compared the abundance of sagebrush songbirds across a gradient of surface disturbance between study periods (trend-by-time). We also assessed changes in the abundance of birds between study periods relative to additional development that had occurred (trend-over-time). We predicted that abundance responses to surface disturbance would be more negative during the second period, regardless of additional disturbance that had occurred, because of previously observed inverse relationships between surface disturbance and nest survival at our sites. Contrary to our predictions, abundance responses attenuated by the second time period for two of three species, Brewer's sparrow and sage thrasher (the latter at one energy field only). Sagebrush sparrow abundance, however, consistently decreased with surface disturbance within and between periods. Sage thrasher abundance consistently decreased with surface disturbance at one of the gas fields, and the probability of colonization by thrashers between study periods was lower where additional surface disturbance had occurred. Our results highlight the importance of revisiting wildlife responses to anthropogenic habitat changes over time, to clarify the severity and longevity of effects.
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Global energy demands continue to result in new and emerging sources of anthropogenic disturbance to populations and systems. Here, we assessed the influence of natural gas development on a critical component of fitness (nest survival) for Brewer’s sparrow (Spizella breweri), sagebrush sparrow (Artemisiospiza nevadensis), and sage thrasher (Oreoscoptes montanus), three species of sagebrush-obligate songbirds that are of conservation concern, and assessed the efficacy of a commonly used index of oil and gas development intensity (well density) for estimating habitat transformation and predicting species’ responses. During 2008–2009 and 2011–2012 we monitored 926 nests within two natural gas fields in western Wyoming, USA. We calculated landscape metrics (habitat loss, amount of edge, patch shape complexity, and mean patch size) to identify the aspect of landscape transformation most captured by well density. Well density was most positively associated with the amount of sagebrush habitat loss within 1 square kilometer. Nest survival was relatively invariant with respect to well density for all three species. In contrast, nest survival rates of all three species generally decreased with surrounding habitat loss due to energy development. Thus, although well density and habitat loss were strongly correlated, well density resulted in overly conservative estimates of nest survival probability. Our results emphasize the importance of careful evaluation of the appropriateness of particular indices for quantifying the effects of human-induced habitat change. For managers concerned about the effects of natural gas development or similar forms of human land use to co-occurring breeding birds, we recommend minimizing the amount of associated habitat conversion.
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(1) Deermice were supplied with extra food between December 1973 and June 1975. (2) Late-winter addition of food to two areas resulted in more male and female deermice. (3) Immigration to areas with extra food was nearly triple that to controls. (4) The size of home ranges of residents became significantly smaller in populations with extra food. (5) Breeding on control areas was delayed in spring 1974, when weather was poor. However, mice on grids with extra food bred early and began to breed in winter. (6) Mice with extra food produced more young and reached sexual maturity at a lower weight. (7) Extra food reversed the normal winter weight loss so that mice maintained high weights and reproduced in spite of temperate winter weather. (8) The annual fluctuations in numbers of deermice may be a consequence of seasonal reproductive behaviour which is proximately limited by food availability.
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Seven of nine common shredder species attained significantly higher adult mass, higher densities, or both when food was supplemented. Larval densities of Malenka spp. and Brilla retifinis were significantly higher when additional food was added. Brillia retifinis densities were >10× greater in high food additions. B. retifinis apparently fills a role as a fugitive in this system and is better able to track shifts in resource abundance by virtue of its short generation time. Zapada cinctipes and Z. haysi were more dense in high and intermediate food input treatments during the last half of the summer. Other taxa had nonsignificant trends to higher densities when extra food was provided. Most of the change in benthic densities can be attributed to decreased rates of emigration with increasing food supply. Six of eight taxa for which adult mass at emergence was measured were significantly more massive (4-46%) when food was added. Females gained proportionately more in most species. The biomass of most taxa increased in proportion to the overall increase in biomass of the common coarse-detritus consumers. The main exceptions were a disproportionate increase in the percentage of the biomass represented by B. retifinis and a decrease in the representation of Z. cinctipes. -from Author
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(1) Population density and reproduction in the song sparrow (Melospiza melodia, Wilson) on Mandarte Island, B.C. varied widely from 1975 to 1986. Several measures of reproductive success declined as population density increased by six times. At peak density, females produced only one-quarter the number of young produced at low densities. (2) We provided supplemental food to sixteen of seventy-two pairs before and during the breeding period in 1985, a year of peak density, to test the hypothesis that the amount of food available per pair declines as density increases and thus regulates reproduction. (3) Supplemental food (i) advanced laying date; (ii) increased clutch size, the number of breeding attempts, nestling weight and the number of independent young produced; and (iii) reduced brood parasitism and the interval between successful nesting attempts. (4) There was no difference in the subsequent survival or reproduction of fed and control young. (5) Supplemental food was associated with reduced adult survival to the next breeding season, perhaps because of increased competition for territories with feeders after the feeding experiment. (6) We conclude that food supply is important in regulating reproduction, and that food availability in the breeding period could limit population size.
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We obtained a complete census of vegetation in a 30- x 1,900-m plot in the Sonoran Desert (Tumamoc Hill, Pima County, Ariz.). We then evaluated the accuracy of 5 sampling techniques commonly used to sample vegetation in deserts: step-point, point-quarter, and 3 line-intercept methods. We compared presence and percent occurrence for each method with the census. The line-intercept (method 3) most closely estimated the census: it was closer for all species occurring on >1% of the site, revealed the least variability relative to sample size for dominant species, and accounted for more (20 of 23) plant species on the study site than the other methods.
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The decline of greater sage grouse (Centrocercus urophasianus) over the last 50 years has raised concern over how natural gas development might affect sage grouse populations. We examined the effects of vehicular activity due to gas-well development near Pinedale, Wyoming, on productivity and movements of sage grouse. In 1998-1999, we captured and radiomarked 48 female sage grouse on 6 leks classified as disturbed or undisturbed, based on the presence or absence of natural gas development within 3 km. The mean distance from disturbed leks to selected nest sites was greater (P=0.019 with outliers removed, P=0.004 with outliers included) than distance moved from undisturbed leks. Nest-initiation rate for hens from disturbed leks was 65%, while hens from undisturbed leks initiated nests 89% (P=0.07) of the time. Nest success at both disturbed and undisturbed leks was 50%. Our results suggest that light traffic disturbance (1-12 vehicles/day) during the breeding season might reduce nest-initiation rates and increase distances moved from leks during nest-site selection. We recommend further investigation concentrating on hen behavior (i.e., distance moved from lek to nest site, breeding behavior, lek attendance), reproductive effort, and nest success in relation to natural gas development as development intensifies.
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A key issue in animal behaviour is the need to understand variation in behavioural responses to human-induced rapid environmental change (HIREC) such as habitat loss, exotic species, pollution, human harvesting and climate change. Why do some individuals show maladaptive behaviours, while others show adaptive responses to evolutionarily novel situations? At present, we lack a unified conceptual framework for generating predictions and guiding empirical and theoretical work on this critical question. Drawing from the concept of ecological traps, I suggest that a conceptual framework for explaining this variation should include four main points: (1) behavioural responses (adaptive or not) are the result of cueeresponse systems, or behavioural 'rules of thumb'; (2) limited or imprecise, unreliable information often underlies suboptimal behaviour; (3) the organism's behavioural flexibility affects its response to novel situations; and (4) evolution (and development) in past environments has shaped cueeresponse systems, responses to imperfect information and degree of behavioural flexibility to be adaptive in past environments, but not necessarily in novel environments. The degree of match/mismatch between past environments and novel environments altered by HIREC is thus a key to explaining adaptive versus maladaptive behaviours. I suggest several existing frameworks that address these four points, and are thus potentially useful for explaining behavioural responses to HIREC: signal detection theory, adaptive plasticity theory, extended reaction norms and cost-benefit theory on variation in learning. I further discuss more complex aspects of reality that would be useful to add to these existing frameworks. (c) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
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This paper analyzes the impact of small-mammal activity on the standing crop of vegetation on areas reclaimed after coal strip- mining in northeastern Wyoming. The small-mammal community included 2 carnivorous, 2 herbivorous, and 4 omnivorous species. Deer mine (Peromysucs maniculatus ) dominated the population on all areas, constituting 85.4% of small mammals live-trapped. Plant species preferred as food by deer mice included sainfoin (Onobrychis viciaefolia), fireweed summercypress, (Kochia scopa- ria), and fourwing saltbush (Atriplex canescens). Grasses had lower preference rankings than forbs. The deer mouse population consumed 20 g/ha/day of plant matter. They consumed 0.11% of the aboveground peak standing crop (PSC) during the growing season, and the consumption of the total small-mammal commun- ity was less than 1% of PSC. However, the PSC of sainfoin was significantly affected by grazing of small-mammal populations. Large tracts of land in the shortgrass prairie of the Northern Great Plains have been strip-mined for coal and require reclama- tion to levels of productivity that existed before the disturbance. Understanding the role of plant-animal interactions in the reestab- lishment of vegetation after reclamation is essential to designing successful reclamation procedures for strip-mined land. Small Mammals can limit the effectiveness of seedings on rangeland (Nelson et al. 1970), burned brushlands (Howard 1950), and dis- rupted forest habitat (Radvanyi 1980. Grazing by small mammals specifically has been found to decrease primary production in arctic tundra (Batzli 1975) and desert scrub (Soholt 1973) and the
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Anti-predator behavior can affect prey growth, reproduction, survival, and generate emergent effects in food webs. Small mammals often lower the cost of predation by altering their behavior in response to shrubs,but the importance of other microhabitat features, such as downed woody debris, for anti-predator behavior is unknown. We used givingup densities to quantify the degree to which downed woody debris alters perceived predation risk by small mammals in southeastern pineforests. We placed 14 foraging trays next to large downed woody debris,shrubs, and in open areas for 12 consecutive nights. Moon illumination, a common indicator of predation risk, led to a similar reduction in small mammal foraging in all three microhabitats (open, downed woody debris,and shrub). Small mammals perceived open microhabitats as riskier than shrub microhabitats, with downed woody debris habitats perceived as being of intermediate risk between shrub and open microhabitats. Despite the presumed benefits of the protective cover of downed woody debris, small mammals may perceive downed woody debris as a relatively risky foraging site in southeastern pine forests where the high diversity and abundance of rodent-eating snakes may provide a primary predatory threat.
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Human-induced rapid environmental change (HIREC; e.g., climate change or exotic species) has caused global species declines. Although behavioral plasticity has buffered some species against HIREC, maladaptive behavioral scenarios called 'evolutionary traps' are increasingly common, threatening the persistence of affected species. Here, we review examples of evolutionary traps to identify their anthropogenic causes, behavioral mechanisms, and evolutionary bases, and to better forecast forms of HIREC liable to trigger traps. We summarize a conceptual framework for explaining the susceptibility of animals to traps that integrates the cost-benefit approach of standard behavioral ecology with an evolutionary approach (reaction norms) to understanding cue-response systems (signal detection). Finally, we suggest that a significant revision of conceptual thinking in wildlife conservation and management is needed to effectively eliminate and mitigate evolutionary traps.
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Try out several plant-herbivore models and find one that seems to fit the oscillations shown by Alaskan lemmings
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Control of mid-sized mammalian predators (hereafter, mesopredators) is sometimes advocated in an attempt to reduce their impact on wildlife populations, particularly economically important (i.e., game) or endangered species. However, mesopredators may play a role in regulating small mammal populations; thus, lethal control of mesopredators may have unintended consequences. The hispid cotton rat (Sigmodon hispidus; hereafter, cotton rat) is one of the most common small mammals in the southeastern United States and is an important prey species for several of the region's predators. Within fire-maintained communities, such as the longleaf pine (Pinus palustris) forests of the Coastal Plain, cotton rat populations dramatically, yet temporarily, decline following prescribed fire. To evaluate the effects of mesopredator removal on cotton rat survival and cause-specific mortality, we conducted a large-scale mesopredator exclusion experiment that incorporated a prescribed fire during the winter of study. Between 18 May 2006 and 20 June 2007, we used radio-telemetry to monitor 252 cotton rats (131 in exclosures and 121 in controls) and documented 184 mortalities. During the 37-week period of monitoring prior to the prescribed fire event, weekly survival of cotton rats was greater in mesopredator exclusion plots. During the 19 weeks following the prescribed fire, there were no differences in weekly survival relative to mesopredator treatment, but fire caused a short-term reduction in weekly survival within both exclosures and controls. Of 36 cotton rats monitored on the date of prescribed fire, 18 were depredated within 1 month, 4 emigrated, and 5 were killed by the fire event. Overall, raptors preyed on cotton rats more in exclosures than in controls, but evidence for compensatory predation (raptor-caused morality greater in exclosures than in controls although survival rates were similar between treatments) only occurred following the prescribed fire event. Our results suggest that managing mesopredators may result in a temporary increase in cotton rat survival, but dormant season prescribed fire removes this effect until well into the following growing season. © 2011 The Wildlife Society.
Article
Oil and natural gas development in the Intermountain West region of North America has expanded over the last 2 decades, primarily within sagebrush dominated landscapes. Although the effects of energy development on high-profile game species such as the greater sage-grouse (Centrocercus urophasianus) have been documented, studies examining responses of non-game birds are lacking. Simultaneously, many songbirds that breed within sagebrush steppe habitats have shown range-wide population declines that are likely due to widespread habitat loss and alteration. We evaluated songbird abundance and species richness across gradients of oil and natural gas development intensity, as indexed by well density, at 3 energy fields (2 natural gas and 1 oil) in the Upper Green River Basin, Wyoming, USA during 2008–2009. While simultaneously accounting for important habitat attributes, increased well density was associated with significant decreases in Brewer's sparrow (Spizella breweri) and sage sparrow (Amphispiza belli) abundance, particularly in the Jonah natural gas field. Vesper sparrows (Pooecetes gramineus) were also negatively influenced by increased well density. Horned larks (Eremophila alpestris) increased with well density in the Pinedale Anticline natural gas field, and sage thrashers (Oreoscoptes montanus) showed no response to energy development. Species richness was not significantly affected by well density. Results suggest that regional declines of some songbird species, especially sagebrush-obligates, may be exacerbated by increased energy development. Understanding the specific mechanisms underlying responses to energy development is an important next step and will aid land managers in the development of effective mitigation and management strategies for the maintenance of stable bird communities in sagebrush habitat. © 2011 The Wildlife Society.
Article
Millions of ducks, geese, and sandhill cranes (Grus canadensis; hereafter cranes) stop in the Central Platte River Valley (CPRV) of Nebraska to store nutrients for migration and reproduction by consuming corn remaining in fields after harvest. We examined factors that influence use of cornfields by cranes and geese (all mid-continent species combined; e.g., Anser, Chen, and Branta spp.) because it is a key step to efficient conservation planning aimed at ensuring that adequate food resources are available to migratory birds stopping in the CPRV. Distance to night-time roost site, segment of the CPRV (west to east), and agricultural practices (post-harvest treatment of cornfields: idle, grazed, mulched, mulched and grazed, and tilled) were the most important and influential variables in our models for geese and cranes. Probability of cornfield use by geese and cranes decreased with increasing distance from the closest potential roosting site. The use of cornfields by geese increased with the density of corn present there during the early migration period, but field use by cranes appeared not to be influenced by early migration corn density. However, probability of cornfield use by cranes did increase with the amount of wet grassland habitat within 4.8 km of the field. Geese were most likely to use fields that were tilled and least likely to use fields that were mulched and grazed. Cranes were most likely to use fields that were mulched and least likely to use fields that were tilled, but grazing appeared not to influence the likelihood of field use by cranes. Geese were more likely to use cornfields in western segments of the CPRV, but cranes were more likely to use cornfields in eastern segments. Our data suggest that managers could favor crane use of fields and reduce direct competition with geese by reducing fall and spring tilling and increasing mulching. Moreover, crane conservation efforts would be most beneficial if they were focused in the eastern portions of the CPRV and in fields as close as possible to both known roosting and large amounts of wet grassland habitats. © 2011 The Wildlife Society.