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At least 1,063 records · Page 59Linked to original sources

USGS2025

Cave records reveal recent origin of North America’s deepest canyon

We explore how and when Hells Canyon, North America’s deepest river gorge (~2,400 m deep), formed, addressing these fundamental questions first posed by W. Lindgren [ The Gold Belt of the Blue Mountains of Oregon (1901)]. Existing hypotheses about the canyon’s formation and timing of incision remain speculative due to a lack of direct constraints and geomorphic analysis in the canyon. Herein, we combine cosmogenic nuclide dating of cave-bound river deposits, river profile analysis, and numerical modeling to provide the first direct age constraints and systematic analysis of incision processes at work in Hells Canyon. Our study reveals a significant drainage capture triggered rapid incision at ~2.1 ± 1.0 Ma, establishing the Snake River’s modern route into the Columbia River system. The increased drainage area and subsequent increase in stream power resulted in the rapid incision of Hells Canyon and the formation of tributary knickpoints (KPs) that decrease in elevation away from the capture location. Cosmogenic dating of cave deposits indicates incision rates increased from ~0.01 to ~0.16 mm y −1 . Numerical modeling of the stream capture supports these observations, demonstrating how abrupt drainage area increase drives rapid river incision. Our findings from Hells Canyon provide a well-constrained example of how drainage capture can dramatically shape the evolution of a major river gorge.

Idaho, Oregon, Washington↗

USGS2014

Prey availability, consumption, and quality contribute to variation in growth of subyearling Chinook Salmon rearing in riverine and reservoir habitats

We examined prey availability, prey consumed, and diet energy content as sources of variation in growth of natural fall Chinook Salmon Oncorhynchus tshawytscha subyearlings rearing in riverine and reservoir habitats in the Snake River. Subyearlings in riverine habitat primarily consumed aquatic insects (e.g., Diptera, Ephemeroptera, Trichoptera), of which a high proportion was represented by adult, terrestrial forms. In the reservoir, subyearlings also consumed aquatic insects but also preyed heavily at times on nonnative lentic amphipods Corophium spp. and the mysid Neomysis mercedis , which were absent in riverine habitats. The availability of prey was typically much higher in the reservoir due to N. mercedis often composing over 90% of the biomass, but when this taxon was removed from consideration, biomass estimates were more often higher in the riverine habitat. Subyearling diets during 2009–2011 were generally 17–40% higher in energy in the riverine habitat than in the reservoir. Observed growth in both length and weight were significantly higher in the riverine habitat than in the reservoir. Little is known about how temporal and spatial changes in the food web in large river landscapes influence populations of native anadromous fishes. Our results provide a glimpse of how the spread and establishment of nonnative prey species can reduce juvenile salmon growth in a large river impoundment, which in turn can affect migration timing and survival.

Washington↗

USGS2015

Re-estimating temperature-dependent consumption parameters in bioenergetics models for juvenile Chinook salmon

Researchers have cautioned against the borrowing of consumption and growth parameters from other species and life stages in bioenergetics growth models. In particular, the function that dictates temperature dependence in maximum consumption ( C max ) within the Wisconsin bioenergetics model for Chinook Salmon Oncorhynchus tshawytscha produces estimates that are lower than those measured in published laboratory feeding trials. We used published and unpublished data from laboratory feeding trials with subyearling Chinook Salmon from three stocks (Snake, Nechako, and Big Qualicum rivers) to estimate and adjust the model parameters for temperature dependence in C max . The data included growth measures in fish ranging from 1.5 to 7.2 g that were held at temperatures from 14°C to 26°C. Parameters for temperature dependence in C max were estimated based on relative differences in food consumption, and bootstrapping techniques were then used to estimate the error about the parameters. We found that at temperatures between 17°C and 25°C, the current parameter values did not match the observed data, indicating that C max should be shifted by about 4°C relative to the current implementation under the bioenergetics model. We conclude that the adjusted parameters for C max should produce more accurate predictions from the bioenergetics model for subyearling Chinook Salmon.

Transactions of the American Fisheries Society↗

USGS2015

Quantifying avian predation on fish populations: integrating predator-specific deposition probabilities in tag-recovery studies

Accurate assessment of specific mortality factors is vital to prioritize recovery actions for threatened and endangered species. For decades, tag recovery methods have been used to estimate fish mortality due to avian predation. Predation probabilities derived from fish tag recoveries on piscivorous waterbird colonies typically reflect minimum estimates of predation due to an unknown and unaccounted-for fraction of tags that are consumed but not deposited on-colony (i.e., deposition probability). We applied an integrated tag recovery modeling approach in a Bayesian context to estimate predation probabilities that accounted for predator-specific tag detection and deposition probabilities in a multiple-predator system. Studies of PIT tag deposition were conducted across three bird species nesting at seven different colonies in the Columbia River basin, USA. Tag deposition probabilities differed significantly among predator species (Caspian terns Hydroprogne caspia : deposition probability = 0.71, 95% credible interval [CRI] = 0.51–0.89; double-crested cormorants Phalacrocorax auritus : 0.51, 95% CRI = 0.34–0.70; California gulls Larus californicus : 0.15, 95% CRI = 0.11–0.21) but showed little variation across trials within a species or across years. Data from a 6-year study (2008–2013) of PIT-tagged juvenile Snake River steelhead Oncorhynchus mykiss (listed as threatened under the Endangered Species Act) indicated that colony-specific predation probabilities ranged from less than 0.01 to 0.17 and varied by predator species, colony location, and year. Integrating the predator-specific deposition probabilities increased the predation probabilities by a factor of approximately 1.4 for Caspian terns, 2.0 for double-crested cormorants, and 6.7 for California gulls compared with traditional minimum predation rate methods, which do not account for deposition probabilities. Results supported previous findings on the high predation impacts from strictly piscivorous waterbirds nesting in the Columbia River estuary (i.e., terns and cormorants), but our findings also revealed greater impacts of a generalist predator species (i.e., California gulls) than were previously documented. Approaches used in this study allow for direct comparisons among multiple fish mortality factors and considerably improve the reliability of tag recovery models for estimating predation probabilities in multiple-predator systems.

Transactions of the American Fisheries Society↗

USGS2016

Avian predation on juvenile Salmonids: Spatial and temporal analysis based on acoustic and passive integrated transponder tags

We evaluated the impact of predation on juvenile steelhead Oncorhynchus mykiss and yearling and subyearling Chinook Salmon O. tshawytscha by piscivorous waterbirds from 11 different breeding colonies in the Columbia River basin during 2012 and 2014. Fish were tagged with both acoustic tags and PIT tags and were tracked via a network of hydrophone arrays to estimate total smolt mortality (1 – survival) at various spatial and temporal scales during out‐migration. Recoveries of PIT tags on bird colonies, coupled with the last known detections of live fish passing hydrophone arrays, were used to estimate the impact of avian predation relative to total smolt mortality. Results indicated that avian predation was a substantial source of steelhead mortality, with predation probability (proportion of available fish consumed by birds) ranging from 0.06 to 0.28 for fish traveling through the lower Snake River and the lower and middle Columbia River. Predation probability estimates ranged from 0.03 to 0.09 for available tagged yearling Chinook Salmon and from 0.01 to 0.05 for subyearlings. Smolt predation by gulls Larus spp. was concentrated near hydroelectric dams, while predation by Caspian terns Hydroprogne caspia was concentrated within reservoirs. No concentrated areas of predation were identified for double‐crested cormorants Phalacrocorax auritus or American white pelicans Pelecanus erythrorhynchos . Comparisons of total smolt mortality relative to mortality from colonial waterbirds indicated that avian predation was one of the greatest sources of mortality for steelhead and yearling Chinook Salmon during out‐migration. In contrast, avian predation on subyearling Chinook Salmon was generally low and constituted a minor component of total mortality. Our results demonstrate that acoustic and PIT tag technologies can be combined to quantify where and when smolt mortality occurs and the fraction of mortality that is due to colonial waterbird predation relative to non‐avian mortality sources.

Transactions of the American Fisheries Society↗

USGS2005

Habitat associations of age-0 cutthroat trout in a spring stream improved for adult salmonids

Native cutthroat trout ( Oncorhynchus clarki ) in the Snake River watershed use streams formed by large springs for spawning and nursery habitat. Several spring streams have been modified to enhance abundance of adult salmonids, but the habitat associations of age-0 cutthroat trout in these systems are undescribed. We assessed the frequency of collection of age-0 cutthroat trout in riffles, riffle margins, pool margins, and backwaters from late June to the middle of August 2000 in a spring stream with such modifications. The proportion of sites in which age-0 cutthroat trout were collected increased up to the middle of July and then decreased. We found substantially lower frequencies of collection of age-0 cutthroat trout in riffles compared to the three stream-margin habitat types. Age-0 cutthroat trout appeared to select shallow, low-velocity, stream-margin habitat with cover that provided protection from piscivorous adult salmonids and avian predators. Our observations suggest that modification of spring streams for production of cutthroat trout should include efforts to manage stream margins so they provide cover in the form of aquatic macrophytes or overhanging vegetation for age-0 fish.

Journal of Freshwater Ecology↗

USGS2011

Biology, status, and management of the yellowstone cutthroat trout

Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri were historically distributed in the Yellowstone River drainage (Montana and Wyoming) and the Snake River drainage (Wyoming, Idaho, Utah, Nevada, and probably Washington). Individual populations evolved distinct life history characteristics in response to the diverse environments in which they were isolated after the last glaciation. Anthropogenic activities have resulted in a substantial decline (42% of the historical range is currently occupied; 28% is occupied by core [genetically unaltered] populations), but the number of extant populations, especially in headwater streams, has precluded listing of this taxon under the Endangered Species Act. Primary threats to persistence of Yellowstone cutthroat trout include (1) invasive species, resulting in hybridization, predation, disease, and interspecific competition; (2) habitat degradation from human activities such as agricultural practices, water diversions, grazing, dam construction, mineral extraction, grazing, timber harvest, and road construction; and (3) climate change, including an escalating risk of drought, wildfire, winter flooding, and rising temperatures. Extirpation of individual populations or assemblages has led to increasing isolation and fragmentation of remaining groups, which in turn raises susceptibility to the demographic influences of disturbance (both human and stochastic) and genetic factors. Primary conservation strategies include (1) preventing risks associated with invasive species by isolating populations of Yellowstone cutthroat trout and (2) connecting occupied habitats (where possible) to preserve metapopulation function and the expression of multiple life histories. Because persistence of isolated populations may be greater in the short term, current management is focused on isolating individual populations and restoring habitats; however, this approach implies that humans will act as dispersal agents if a population is extirpated because of stochastic events.

Idaho, Montana, Utah, Wyoming↗

USGS2014

Performance of a surface bypass structure to enhance juvenile steelhead passage and survival at Lower Granite Dam, Washington

An integral part of efforts to recover stocks of Pacific salmon Oncorhynchus spp. and steelhead O. mykiss in Pacific Northwest rivers is to increase passage efficacy and survival of juveniles past hydroelectric dams. As part of this effort, we evaluated the efficacy of a prototype surface bypass structure, the removable spillway weir (RSW), installed in a spillbay at Lower Granite Dam, Washington, on the Snake River during 2002, 2003, 2005, and 2006. Radio-tagged juvenile steelhead were released upstream from the dam and their route of passage through the turbines, juvenile bypass, spillway, or RSW was recorded. The RSW was operated in an on-or-off condition and passed 3–13% of the total discharge at the dam when it was on. Poisson rate models were fit to the passage counts of hatchery- and natural-origin juvenile steelhead to predict the probability of fish passing the dam. Main-effect predictor variables were RSW operation, diel period, day of the year, proportion of flow passed by the spillway, and total discharge at the dam. The combined fish passage through the RSW and spillway was 55–85% during the day and 37–61% during the night. The proportion of steelhead passing through nonturbine routes was <88% when the RSW was off during the day and increased to >95% when the RSW was on during the day. The ratio of the proportion of steelhead passed to the proportion of water passing the RSW was from 6.3:1 to 10.0:1 during the day and from 2.7:1 to 5.2:1 during the night. Steelhead passing through the RSW exited the tailrace about 15 min faster than fish passing through the spillway. Mark–recapture single-release survival estimates for steelhead passing the RSW ranged from 0.95 to 1.00. The RSW appeared to be an effective bypass structure compared with other routes of fish passage at the dam.

Idaho, Oregon, Washington↗

USGS2014

A semi-automated method of monitoring dam passage of American Eels Anguilla rostrata

Fish passage facilities at dams have become an important focus of fishery management in riverine systems. Given the personnel and travel costs associated with physical monitoring programs, automated or semi-automated systems are an attractive alternative for monitoring fish passage facilities. We designed and tested a semi-automated system for eel ladder monitoring at Millville Dam on the lower Shenandoah River, West Virginia. A motion-activated eel ladder camera (ELC) photographed each yellow-phase American Eel Anguilla rostrata that passed through the ladder. Digital images (with date and time stamps) of American Eels allowed for total daily counts and measurements of eel TL using photogrammetric methods with digital imaging software. We compared physical counts of American Eels with camera-based counts; TLs obtained with a measuring board were compared with TLs derived from photogrammetric methods. Data from the ELC were consistent with data obtained by physical methods, thus supporting the semi-automated camera system as a viable option for monitoring American Eel passage. Time stamps on digital images allowed for the documentation of eel passage time—data that were not obtainable from physical monitoring efforts. The ELC has application to eel ladder facilities but can also be used to monitor dam passage of other taxa, such as crayfishes, lampreys, and water snakes.

North American Journal of Fisheries Management↗

USGS2013

Water supply, demand, and quality indicators for assessing the spatial distribution of water resource vulnerability in the Columbia River Basin

We investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality. Based on the US county scale, spatial analysis was conducted using various biophysical and socio-economic indicators that control water vulnerability. Water supply vulnerability and water demand vulnerability exhibited a similar spatial clustering of hotspots in areas where agricultural lands and variability of precipitation were high but dam storage capacity was low. The hotspots of water quality vulnerability were clustered around the main stem of the Columbia River where major population and agricultural centres are located. This multiple equal weight indicator approach confirmed that different drivers were associated with different vulnerability maps in the sub-basins of the CRB. Water quality variables are more important than water supply and water demand variables in the Willamette River basin, whereas water supply and demand variables are more important than water quality variables in the Upper Snake and Upper Columbia River basins. This result suggests that current water resources management and practices drive much of the vulnerability within the study area. The analysis suggests the need for increased coordination of water management across multiple levels of water governance to reduce water resource vulnerability in the CRB and a potentially different weighting scheme that explicitly takes into account the input of various water stakeholders.

Atmosphere - Ocean↗

USGS2021

Effects of climate and irrigation on GRACE-based estimates of water storage changes in major US aquifers

Understanding climate and human impacts on water storage is critical for sustainable water-resources management. Here we assessed climate and human drivers of total water storage (TWS) variability from Gravity Recovery and Climate Experiment (GRACE) satellites compared with drought severity and irrigation water use in 14 major aquifers in the United States. Results show that long-term variability in TWS tracked by GRACE satellites is dominated by interannual variability in most of the 14 major US aquifers. Low TWS trends in the humid eastern U.S. are linked to low drought intensity. Although irrigation pumpage in the humid Mississippi Embayment aquifer exceeded that in the semi-arid California Central Valley, a surprising lack of TWS depletion in the Mississippi Embayment aquifer is attributed to extensive streamflow capture. Marked storage depletion in the semi-arid southwestern Central Valley and south-central High Plains totaled ∼90 km 3 , about three times greater than the capacity of Lake Mead, the largest U.S. reservoir. Depletion in the Central Valley was driven by long-term droughts (⩽5 yr) amplified by switching from mostly surface water to groundwater irrigation. Low or slightly rising TWS trends in the northwestern (Columbia and Snake Basins) US are attributed to dampening drought impacts by mostly surface water irrigation. GRACE satellite data highlight synergies between climate and irrigation, resulting in little impact on TWS in the humid east, amplified TWS depletion in the semi-arid southwest and southcentral US, and dampened TWS deletion in the northwest and north central US Sustainable groundwater management benefits from conjunctive use of surface water and groundwater, inefficient surface water irrigation promoting groundwater recharge, efficient groundwater irrigation minimizing depletion, and increasing managed aquifer recharge. This study has important implications for sustainable water development in many regions globally.

Environmental Research Letters↗

USGS2021

Understanding metrics of stress in the context of invasion history: The case of the brown treesnake (Boiga irregularis)

Invasive species can exert rapid depletion of resources after introduction and, in turn, affect their own population density. Additionally, management actions can have direct and indirect effects on demography. Physiological variables can predict demographic change but are often restricted to snapshots-in-time and delayed confirmation of changes in population density reduces their utility. To evaluate the relationships between physiology and demography, we assessed metrics of individual and demographic stress (baseline and 1-h corticosterone (CORT), body condition and bacterial killing ability) in the invasive snake Boiga irregularis on Guam collected in intervals of 10–15 years. We also assessed potential discrepancies between different methods of measuring hormones [radioimmunoassay (RIA) versus enzyme immunoassay (EIA)]. The magnitude of difference between RIA and EIA was negligible and did not change gross interpretation of our results. We found that body condition was higher in recent samples (2003 and 2018) versus older (1992–93) samples. We found corresponding differences in baseline CORT, with higher baseline CORT in older, poorer body condition samples. Hormonal response to acute stress was higher in 2018 relative to 2003. We also found a weak relationship between circulating CORT and bacterial killing ability among 2018 samples, but the biological significance of the relationship is not clear. In an effort to develop hypotheses for future investigation of the links between physiology and demography in this and other systems, we discuss how the changes in CORT and body condition may reflect changes in population dynamics, resource availability or management pressure. Ultimately, we advocate for the synchronization of physiology and management studies to advance the field of applied conservation physiology.

Conservation Physiology↗

USGS2025

Fate and effects to the benthic community of a copper treatment to eradicate invasive mussels in a large western river, USA

Copper-based chemical treatments are commonly used to eradicate invasive mussels in small ponds and lakes, but their use in large rivers has been limited. In 2023, in response to a detection of invasive quagga mussels, a 10-km reach of the Snake River (Idaho, USA), was treated with an unprecedented 19,300 kg of chelated copper molluscicide to a target concentration of 1,000 µg/L for 10 days. We assessed the transport and fate of the copper and its exposure and effects on the nontarget benthic community downstream. Water samples were collected at seven locations throughout the treatment period, and sediment, periphyton, and benthic macroinvertebrates were collected pre- and posttreatment. Nearly half of the original mass of copper was removed from the water column via sedimentation, sorption to algae, or biological uptake within the 10-km treatment reach and the first 15 km downstream. Even so, dissolved copper concentrations exceeded the acute toxicity threshold at least as far as 28 km downstream for more than 2 weeks. Sediment copper increased by up to 8.3-fold, exceeding the consensus-based sediment quality threshold effect concentration at several sites. Effects on benthic macroinvertebrates varied by taxa. From 0–28 km downstream, invertebrate abundances decreased 52%–94%, with gastropods among the most affected. Of the unique taxa present at these sites pretreatment, 52%–64% were not found posttreatment but were replaced by other taxa, indicating a reorganization of the base of the food web. Additionally, from 0–15 km downstream, the percentage of individuals from tolerant taxa increased two to15-fold. Findings from this study can help watershed managers plan future invasive mussel responses while protecting culturally, economically, and ecologically important nontarget species in large rivers.

Idaho↗

USGS2020

Residues of organochlorine insecticides, polychlorinated biphenyls, and heavy metals in biota from Apalachicola River, Florida, 1978

Seventy-seven composite samples composed of largemouth bass ( Micropterus salmoides ), channel catfish ( Ictaluras punctatus ), threadfin shad ( Dorosoma petenense ), Asiatic clam ( Corbicula fluminea ), burrowing mayfly ( Hexagenia sp.), water snake ( Natrix spp.), and little green heron ( Butorides virescens ) were collected from upper and lower reaches of the Apalachicola River, Florida, in 1978 for residue analysis of organochlorine insecticides, PCBs (polychlorinated biphenyls), and metals. Compared with data from the National Pesticide Monitoring Program and criteria recommended for the protection of aquatic life, residue concentrations were moderately high in the Apalachicola River. Biota from the upper river generally had higher organic and lower metal residues than those from the lower river. Highest residues in the biota were total DDT, total PCBs, and toxaphene. Although individual mean concentrations were below 2 μg/g and total organic contaminant residues never exceeded 5 μg/g, residue concentrations of DDT, PCBs, and toxaphene (particularly from the upper river) exceeded recommended permissible levels for the protection of aquatic life. Metal residues were generally below 1 μg/g. Exceptions were arsenic residues in threadfin shad (1.07 μg/g) and Asiatic clams (1.75 μg/g), and selenium in eggs of channel catfish (1.39 μg/g). The residues observed in the biota, particularly from the upper station, indicated moderate contamination of the Apalachicola River system at the time samples were collected.

Journal of the Association of Official Analytical ↗

USGS2024

Duckling survival increased with availability of flooded wetland habitat and decreased with salinity concentrations in a brackish marsh

Waterfowl population recruitment is sensitive to duckling survival. We quantified predator types and survival rates for Anas platyrhynchos (Mallard) and Mareca strepera (Gadwall) ducklings in one of the largest brackish water marshes in western North America (Suisun Marsh, California) using 556 radio-tagged ducklings from 284 broods tracked during the 2016 to 2019 breeding seasons. Overall, 78% of ducklings died and 84% of mortalities occurred < 7 days after hatch. After hatching in upland fields, survival was greater for broods that hatched closer to flooded wetlands; broods had a ≥ 75% chance of surviving the move from the nest to water when nests were located ≤ 140 m from the nearest wetland and ≤ 50% chance of surviving when nests were located ≥ 970 m from the nearest wetland. Predation accounted for 91% of mortalities and was attributed to mammals (27.6%), birds (22.0%), snakes (4.4%), and unknown predators (46.0%). Anas platyrhynchos survival to fledging (54 days) was only 3.2% and 0.9% during 2 drier years and 11.7% and 16.7% during 2 wetter years. Mareca strepera survival to fledging was 9.4% to 11.2% among years. Daily survival rates for ducklings generally increased with the amount of flooded wetlands within 0.5 km ( A. platyrhynchos ) and 1.0 km ( M. strepera ) of the nest at hatch. Additionally, survival rates increased with duckling age and body mass at hatch for both species and decreased with hatch date for A. platyrhynchos but not M. strepera , which may be partially due to the earlier onset of A. platyrhynchos nesting. For ducklings that survived the initial move to water, survival rates were negatively correlated with salinity and this effect was more pronounced for younger ducklings. Anas platyrhynchos survival to 7 days post hatch decreased by 9.1% (wetter year) to 31.4% (drier year) when ducklings were in 12 ppt water (99th quantile of cumulative salinity concentrations experienced by ducklings) versus 0.5 ppt water. Mareca strepera survival to 7 days decreased by 7.4% when ducklings were in 12 ppt vs. 0.5 ppt water. Our results suggest that maintaining a network of low salinity wetlands within 1 km of upland nesting sites would likely improve duckling survival rates, especially during the critical 7-day period after hatch.

California↗

USGS2024

Illegal shooting of protected nongame birds along power lines coincides with places and times of peak legal recreational shooting

Illegal killing of protected nongame birds is pervasive and can be demographically relevant. In 2021 and 2022, we evaluated spatial and temporal patterns in illegal killing of birds along 69.7 km of power lines in the Morley Nelson Snake River Birds of Prey National Conservation Area in Idaho, USA, to provide insight into potential drivers behind the activity and key information to manage this threat across the American west. The illegal shooting of 8 species of raptors and corvids we documented was clumped both temporally and spatially, as opposed to being randomly distributed across the year and landscape. We found 72 illegally shot birds, most killed during spring months (March to May), coincident with peak time periods of legal recreational shooting activity, and in places with high levels of recreational shooting. We also found evidence of targeted killing of raptors in the conservation area in areas not associated with recreational shooting. Given the numbers of nesting pairs of some local raptor species, this shooting is likely demographically relevant for some but not all local populations. Likewise, with the prevalence of recreational shooting across the American west, the inference we draw is broadly relevant beyond our Idaho study area. The insight our work provides can enable owners of power lines, law enforcement agencies, and resource managers to coordinate in outreach, regulatory, and law enforcement action to manage a threat that may have widespread impacts for some avian species.

Idaho↗

USGS2025

Landscape changes and declines in Aquila chrysaetos (Golden Eagle) territory occupancy in southwestern Idaho

Rapid loss of native shrubs and expansion of invasive annual plants like cheatgrass ( Bromus tectorum ) have altered North American shrub-steppe systems across extensive areas. Predators, like Aquila chrysaetos (Golden Eagle) that forage on shrub-reliant prey, may abandon historically occupied territories or increase their territory size to cope with degraded habitat. We used a multiseason Bayesian occupancy model that accounted for imperfect detection to investigate the associations between landscape cover, fire history, conspecific neighbor density, and occupancy of 36 A. chrysaetos territories in southwestern Idaho and the Morley Nelson Snake River Birds of Prey National Conservation Area, USA from 1986 to 2022. The probability of A. chrysaetos occupancy at historically occupied territories decreased 25% from 1986 to 2022 (0.83–0.58). Once territories became vacant for 5 yr, they tended to remain vacant, suggesting that they were no longer suitable for eagles, or that no new eagles were recruiting into the population. Territory occupancy was positively associated with shrub cover ( β : 0.90, 95% CrI: 0.12 to 1.71) and negatively (albeit weakly) associated with annual herbaceous cover ( β : –0.63, 95% CrI: –1.32 to 0.05). Territories closer to other occupied territories had a lower probability of occupancy than territories with distant neighbors ( β : –3.89, 95% CrI: –4.61 to –3.14), likely because eagles compensated for degraded habitat by expanding their territories. Years since the territory last burned had a slightly positive effect on occupancy with high uncertainty and a credible interval that overlapped 0 ( β : 0.28, 95% CrI: –0.26 to 0.87). The probability of detecting eagles in an occupied territory was high (0.90) and improved in surveys conducted earlier in the day and later in the breeding season. Shrub conversion to invasive grasslands has negative bottom-up consequences on A. chrysaetos territory occupancy, which may decrease the local carrying capacity for eagles in this area.

Idaho↗

USGS2009

Magma evolution and ascent at the craters of the moon and neighboring volcanic fields, southern Idaho, USA: Implications for the evolution of polygenetic and monogenetic volcanic fields

The evolution of polygenetic and monogenetic volcanic fields must reflect differences in magma processing during ascent. To assess their evolution we use thermobarometry and geochemistry to evaluate ascent paths for neighboring, nearly coeval volcanic fields in the Snake River Plain, in south-central Idaho, derived from (1) dominantly Holocene polygenetic evolved lavas from the Craters of the Moon lava field (COME) and (2) Quaternary non-evolved, olivine tholeiites (NEOT) from nearby monogenetic volcanic fields. These data show that NEOT have high magmatic temperatures (1205 + or - 27 degrees C) and a narrow temperature range (< 25 degrees C) at any given depth; NEOT parent magmas partially crystallize within the middle crust (14-17 km), but with little time for cooling or assimilation. In contrast, COME magmas partially crystallize at similar depths, but at any given depth exhibit lower temperatures (by ~40 degrees C), and wider temperature ranges (>50 degrees C). Prolonged storage of COME magmas allows them to evolve to higher 87 Sr/ 86 Sr and SiO 2 , and lower MgO and 143 Nd/ 144 Nd. Most importantly, ascent paths control evolution: NEOT often erupt near the axis of the plain where high-flux (Yellowstone-related), pre-Holocene magmatic activity replaces granitic middle crust with basaltic sills, resulting in a net increase in NEOT magma buoyancy. COME flows erupt off-axis, where felsic crustal lithologies sometimes remain intact, providing a barrier to ascent and a source for crustal contamination. A three-stage ascent process explains the entire range of erupted compositions. Stage 1 (40-20 km): picrites are transported to the middle crust, undergoing partial crystallization of olivine + or - clinopyroxene. COME magmas pass through unarmored conduits and assimilate 1% or less of ancient gabbroic crust having high Sr and 87 Sr/ 86 Sr and low SiO 2 . Stage 2 (20-10 km): magmas are stored within the middle crust, and evolve to moderate MgO (10%). NEOT magmas, reaching 10% MgO, are positively buoyant and migrate through the middle crust. COME magmas remain negatively buoyant and so crystallize further and assimilate middle crust. Stage 3 (15-0 km): final ascent and eruption occurs when volatile contents, increased by differentiation, are sufficient (1-2 wt % H 2 O) to provide magma buoyancy through the middle (and upper) crust.

Idaho↗