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At least 109 records · Page 6Linked to original sources
USGS2024

Vegetation responses to large dam removal on the Elwha River, Washington, USA

Large dam removal can trigger changes to physical and biological processes that influence vegetation dynamics in former reservoirs, along river corridors downstream of former dams, and at a river’s terminus in deltas and estuaries. We present the first comprehensive review of vegetation response to major fluvial disturbance caused by the world’s largest dam removal. After being in place for nearly a century, two large dams were removed along the Elwha River, Washington, USA, between 2011 and 2014. The exposure, erosion, transport, and deposition of large volumes of sediment and large wood that were impounded behind the dams created new fluvial surfaces where plant colonization and growth have occurred. In the former reservoirs, dam removal exposed ~290 ha of unvegetated sediment distributed on three main landforms: valley walls, high terraces, and dynamic floodplains. In addition to natural revegetation in the former reservoirs, weed control and seeding and planting of desirable plants influenced vegetation trajectories. In early years following dam removal, ~20.5 Mt of trapped sediment were eroded from the former reservoirs and transported downstream. This sediment pulse, in combination with transport of large wood, led to channel widening, an increase in gravel bars, and floodplain deposition. The primary vegetation responses along the river corridor were a reduction in vegetated area associated with channel widening, plant establishment on new gravel bars, increased hydrochory, and altered plant community composition on gravel bars and floodplains. Plant species diversity increased in some river segments. In the delta, sediment deposition led to the creation of ~26.8 ha of new land surfaces and altered the distribution and dynamics of intertidal water bodies. Vegetation colonized ~16.4 ha of new surfaces: mixed pioneer vegetation colonized supratidal beach, river bars, and river mouth bars, and emergent marsh vegetation colonized intertidal aquatic habitats. In addition to the sediment-dominated processes that have created opportunities for plant colonization and growth, biological processes such as restored hydrochory and anadromous fish passage with associated delivery of marine-derived nutrients may influence vegetation dynamics over time. Rapid changes to landforms and vegetation growth were related to the large sediment pulse in the early years following dam removal, and the rate of change is expected to attenuate as the system adjusts to natural flow and sediment regimes.

Washington↗
USGS2024

Time of year and weather influence departure decisions of sandhill cranes at a primary stopover

The Rocky Mountain Population (RMP) of greater sandhill cranes uses a key stopover area, the San Luis Valley (SLV) in Colorado. Parameters of migration phenology can differ between autumn and spring and are affected by weather and environmental factors. We hypothesized that sandhill cranes in the SLV would have a longer stopover duration in autumn than in spring, and that wind assistance, crosswinds, temperature change, barometric air pressure, and surface water area would influence persistence probability. We used data from sandhill cranes fitted with transmitters that spanned autumn and spring, 2015-2022. We used an open robust design mark-recapture model to estimate stopover duration, arrival probability, and persistence probability. We examined the effects of weather and surface water on the persistence probability for 106 sandhill cranes in the SLV. Stopover duration was longer in autumn than in spring and had higher variability across years. Arrival probability to the SLV peaked on 13 October in autumn and 21 February in spring. Persistence probability declined around mid-December in autumn and mid-March in spring. We found that several weather covariates influenced persistence in both seasons. In autumn, sandhill cranes departed the SLV with higher tailwinds, lower crosswinds, and higher surface water availability. In spring, sandhill cranes departed the SLV with lower crosswinds and higher barometric air pressure at the surface and higher wind speeds at altitudes of about 3,000 m. The effect of wind speed was stronger later in the spring. Given the lower variability of arrival and persistence probability and shorter stopover duration in spring compared to autumn, we suspect that RMP sandhill cranes are using a time-minimization strategy during spring. However, given the use of supportive winds and weather conditions ideal for soaring, RMP sandhill cranes appear to be using strategies that save energy in both seasons. Our study identifies the optimal timing of water management and surveys for RMP sandhill cranes and confirms that weather influences their persistence. Understanding differences in migration patterns between seasons and the factors that influence persistence at stopover sites will also be important for anticipating phenological impacts from climate change and land use alterations.

Frontiers in Ecology and Evolution↗
USGS2024

Milkweed and floral resource availability for monarch butterflies (Danaus plexippus) in the United States

The global decline of pollinators, particularly insects, underscores the importance of enhanced monitoring of their populations and habitats. However, monitoring some pollinator habitat is challenging due to widespread species distributions and shifts in habitat requirements through seasons and life stages. The monarch butterfly ( Danaus plexippus ), a migratory insect pollinator that breeds widely throughout North America, presents a unique case study for testing a sampling framework to overcome these challenges. Monarchs exhibit discrete resource needs across life stages (e.g., larval requirement for milkweed, adult requirement for floral nectar), utilizing many land use types across their extensive geographic range during breeding and migration seasons. The Integrated Monarch Monitoring Program (IMMP) uses a standardized protocol with a generalized random tessellation stratified (GRTS) sampling design to gather spatially balanced and ecologically representative information on monarch habitats within the United States. The IMMP is applicable to various land use types and habitats used by breeding monarchs and may be extended to sites outside of the GRTS design to collect data on non-random sites of interest, such as legacy or conservation sites. Additionally, the IMMP’s modular design and publicly available training allows for broad participation, including involvement from community scientists. Here, we summarize habitat metrics (milkweed and floral resources) across 1,233 sites covering much of the monarch’s breeding range. We examine variation in milkweed density and floral resource availability on probabilistic (random) and non-probabilistic (convenience) samples and among land use types (site types). Additionally, we assess resource availability within core geographies for monarch breeding and migration, specifically within the U.S. Fish and Wildlife Service’s Monarch Conservation Units (western, northern, and southern United States). Milkweed density, floral frequency, and floral richness were higher on non-random sites and in the North region. Among site types, milkweed density was highest on Rights-of-Way and Unclassified Grassland, while floral frequency was lowest on Rights-of-Way. The IMMP represents the first field-based habitat monitoring program of this scale for monarchs, yielding a robust dataset on monarchs and their habitats across their breeding range and offering a framework for surveying the habitat of insect species with diverse habitat requirements or widespread distributions.

Frontiers in Ecology and Evolution↗
USGS2024

Benthic macroinvertebrate response to estuarine emergent marsh restoration across a delta-wide environmental gradient

Benthic invertebrates play vital roles in estuarine ecosystems, but like other taxa they have been excluded from former marshlands by diking and land use conversion. Dike removal is one way of restoring marsh, but the response of benthic invertebrates has been little studied. Also understudied is variation in benthic invertebrate communities across entire deltas, particularly in the Pacific Northwest of North America where deltas receive high flows and sediment loads for their size. Our goals were to evaluate invertebrate response to large-scale dike removal on the Nisqually River Delta in Puget Sound, Washington, U.S.A., characterize delta-wide invertebrate community variation, and relate invertebrate response and spatial variation to environmental conditions. We sampled invertebrates annually from one year before to three years after dike removal in restoring marsh, previously restored marsh, undisturbed reference marsh, and adjacent tidal flats. Marine taxa immediately colonized the area recently restored to tidal inundation and population size grew exponentially thereafter for several of them. Community composition and diversity recovered completely, and density and biomass were approaching recovery three years later. Invertebrate communities converged between restoring and pre-existing marsh (previously restored and reference), suggesting an influence of reestablished connectivity. Just offshore from the dike line, invertebrates declined one year after dike removal but then rebounded indicating resilience to short-term disturbance. Dike removal effects were not detected farther offshore. Near the offshore edge of the delta, invertebrate biomass and body size were greater than elsewhere and a diverse assemblage of crustaceans, polychaetes, and bivalves was present. Farther inshore, tidal flats were dominated by a few species of small-bodied polychaetes and had higher density but lower biomass and diversity. Facultative detritivores, which can also filter feed, were the dominant feeding guild everywhere on the tidal flats. Density, biomass, diversity, and community composition on the marsh were more similar to the inner than outer tidal flats. Environmental variables most associated with invertebrate community variation were elevation, salinity, and sediment grain size and organic content. Our results are relevant to assessing performance and setting expectations for future restorations and have broad implications for the role of benthic invertebrates in estuarine ecosystems.

Washington↗
USGS2024

Challenges creating monarch butterfly management strategies for electric power companies in the United States

Returning monarch butterflies ( Danaus plexippus ) to sustainable levels of abundance will require an array of contributors to protect and restore habitat over broad areas. Due to the diversity and scale of land managed by electric power companies across the monarch range, plus an additional 32 million hectares needed for new solar arrays by 2050 to meet renewable energy goals, the industry may have potential to contribute to monarch conservation. However, it is challenging to clearly understand an individual company’s potential for monarch conservation because of the scale and distribution of their specific land assets (ranging from 4,800 to 240,000 hectares in this study alone), the complexity of monarch science, and the lack of a science-based approach for evaluating large land assets for monarch habitat. With monarchs potentially being protected under the United States Endangered Species Act in the future and thereby limiting land management approaches, there is interest from electric power companies to understand how their lands relate to monarchs. In collaboration with companies, we developed a GIS-based model to identify company landholdings that contain high-quality monarch habitat and applied the model to specific landholdings of eight power companies in the United States. We then facilitated discussions with company teams to balance conservation goals, corporate risk, and social opinion. This paper describes non-confidential results for developing a national GIS-based monarch habitat model and applying it to electric power companies who are considering monarch conservation while simultaneously transitioning to a new clean energy future. The model and applied experience may be useful for other organizations working across large landscapes to manage monarchs.

conterminous United States↗
USGS2024

Population and spatial dynamics of desert bighorn sheep in Grand Canyon during an outbreak of respiratory pneumonia

Introduction: Terrestrial species in riverine ecosystems face unique constraints leading to diverging patterns of population structure, connectivity, and disease dynamics. Desert bighorn sheep ( Ovis canadensis nelsoni ) in Grand Canyon National Park, a large native population in the southwestern USA, offer a unique opportunity to evaluate population patterns and processes in a remote riverine system with ongoing anthropogenic impacts. We integrated non-invasive, invasive, and citizen-science methods to address questions on abundance, distribution, disease status, genetic structure, and habitat fragmentation. Methods: We compiled bighorn sightings collected during river trips by park staff, commercial guides, and private citizens from 2000–2018 and captured bighorn in 2010–2016 to deploy GPS collars and test for disease. From 2011–2015, we non-invasively collected fecal samples and genotyped them at 9–16 microsatellite loci for individual identification and genetic structure. We used assignment tests to evaluate genetic structure and identify subpopulations, then estimated gene flow and recent migration to evaluate fragmentation. We used spatial capture-recapture to estimate annual population size, distribution, and trends after accounting for spatial variation in detection with a resource selection function model. Results and discussion: From 2010–2018, 3,176 sightings of bighorn were reported, with sightings of 56–145 bighorn annually on formal surveys. From 2012–2016, bighorn exhibiting signs of respiratory disease were observed along the river throughout the park. Of 25 captured individuals, 56% were infected by Mycoplasma ovipneumoniae , a key respiratory pathogen, and 81% were recently exposed. Pellet sampling for population estimation from 2011–2015 yielded 1,250 genotypes and 453 individuals. We detected 6 genetic clusters that exhibited mild to moderate genetic structure ( F ST 0.022–0.126). The river, distance, and likely topography restricted recent gene flow, but we detected cross-river movements in one section via genetic recaptures, no subpopulation appeared completely isolated, and genetic diversity was among the highest reported. Recolonization of one large stretch of currently empty habitat appears limited by the constrained topology of this system. Annual population estimates ranged 536–552 (95% CrI range 451–647), lamb:ewe ratios varied, and no significant population decline was detected. We provide a multi-method sampling framework useful for sampling other wildlife in remote riverine systems.

Arizona↗
USGS2024

Turning setbacks into stepping-stones for growth in conservation paleobiology

Conservation paleobiology is a cross-disciplinary field that utilizes the geohistorical record of past life on Earth to inform present-day decisions in conservation and restoration and assist in planning for future natural resource management. However, information on how past ecosystems and species responded to environmental change over decadal to millennial timescales is rarely incorporated into conservation and restoration decision-making. To heighten awareness among conservation and restoration practitioners of the relevance of geohistorical data and to bridge the gap between research and implementation in conservation paleobiology, we proposed a Research Topic titled “ Integrating Conservation Biology and Paleobiology to Manage Biodiversity and Ecosystems in a Changing World ”. The 21 articles subsequently published demonstrate the diversity and breadth of geohistorical information available to resource management and the challenges of translating these results into conservation practice and policy. Here we discuss the lessons we learned from editing the Research Topic and suggest a pathway forward for conservation paleobiologists who aspire to generate actionable research results to solve current problems in biodiversity conservation and ecological restoration.

Frontiers in Ecology and Evolution↗
USGS2024

Large-scale dam removal and ecosystem restoration

Rivers underpin vital ecosystems that support aquatic and terrestrial biodiversity and many ecosystem services, including food, water, culture, and recreation ( Dudgeon et al. 2006 ). After centuries of building dams on rivers across the world, river restoration via dam removal is receiving increased public attention, financial investment, and scientific study because of various issues of regarding dam infrastructure, such as obsolescence, sedimentation, and ecosystem degradation ( Duda and Bellmore, 2022 ; East and Grant, 2023 ). Most dam removal projects to date have focused on smaller structures, but larger structures > 10 m tall have also started to be removed in increasing numbers. Recent estimates suggest that only a small fraction of all dam removals have been scientifically studied, with most focused on small dams and short time scales ( Bellmore et al., 2016 ). Understanding the outcomes of large dam removal, where case studies are much more limited, depends on sustained research and monitoring efforts aimed at understanding restoration processes over large spatial and temporal scales ( Figure 1 ). The ecological and socio-ecological study of large dam removal represents a new frontier in dam removal research: projects are larger, more recent, and provide an opportunity to understand the complex ecological changes and impacts to humans that occur with these transformative restoration projects.

Frontiers in Ecology and Evolution↗
USGS2024

Editorial: Subsurface microbiology within hydrocarbon resources or stored gases

A Research Topic on the microbiology of hydrocarbon and gas storage reservoirs has far reaching industrial applications. In recent decades, there has been a growing interest in understanding microbial communities in subsurface energy reservoirs, such as coal, oil, and shale beds. This area of research has broadened to include gas storage reservoirs for hydrogen and CO 2 . Scientists are beginning to unravel the unexpected impact microorganisms have on these systems, through changing the fluid geochemistry, the gas content, and even the permeability. By recognizing the influence of these tiny organisms on our engineered environments, we can develop better risk assessments, target mitigation strategies, expand energy production, and refine operational guidance, ultimately contributing to a more sustainable energy future.

Frontiers in Ecology and Evolution↗
USGS2025

Evidence for marine-driven, cyclical fluctuations in burrow-nesting seabird habitat on the Oregon Coast

Seabirds are among the most threatened birds globally, with the loss or deterioration of coastal breeding habitats posing a severe threat. Natural and anthropogenic disturbances substantially influence coastal ecosystems through erosion and vegetation loss, altering habitat for the wildlife species that depend on them. In addition to these disturbances, oceanographic processes may play an important role in shaping the vegetation at breeding habitats; however, there is limited information on how vegetative conditions for burrow nesting seabirds have changed over time, and whether these changes are related to specific oceanographic or climatic factors. The Oregon Coast National Wildlife Refuge Complex, USA (NWRC) is home to a diverse suite of 1.3 million nesting seabirds from 14 species, which provide valuable ecological, economic, and cultural services, including nutrient transfer to terrestrial habitats and ecotourism for local communities. Over the last 30 years, populations of several burrow nesting seabird species including tufted puffin ( Fratercula cirrhata ) and rhinoceros auklet ( Cerorhinca monocerata ), which breed on offshore islands, have sharply declined along the Oregon Coast. To better understand the potential factors driving these declines, we conducted a spatiotemporal analysis of an aspect of burrow nesting seabird habitat, vegetation cover, within the Oregon Coast NWRC. Specifically, we quantified vegetative cover on 16 islands from 1992 to 2022 using a combination of empirical data, historical aerial photography (1992–2005), and aerial photography from the National Agriculture Imagery Program (2005–2022). Results showed cyclical fluctuations in vegetation cover coast-wide, which were closely related to large scale oceanographic oscillations. Specifically, vegetation cover was negatively correlated with the winter Pacific Decadal Oscillation and positively correlated with the spring El Nino Southern Oscillation. We did not directly compare seabird population trends to vegetation trends; however, quantifying these long-term changes in vegetation at breeding habitats can contribute to our comprehensive understanding of the myriad factors influencing seabird population dynamics and conservation.

Oregon↗
USGS2025

Spatiotemporal risk avoidance varies seasonally, relative to risk intensity, in a reestablishing predator–prey system

Predation establishes risk, which can indirectly influence prey behavior and ecology. We evaluated the influence of Mexican gray wolves ( Canis lupus baileyi ) on habitat selection and spatiotemporal predator avoidance strategies of elk ( Cervus canadensis ). We fit 866 adult female elk with GPS collars across areas of varying wolf densities within the Mexican wolf experimental population area of eastern Arizona and western New Mexico between 2019−2021. Using step-selection functions we examined relative intensity of elk use in relation to landscape attributes, estimated predator/prey diel activity, and measures of risk. Risk metrics included predicted wolf presence, habitat openness, and predicted risky places modeled from attributes of locations where wolves killed elk. Wolf activity varied across seasons and increased midday and night in fall and monsoon seasons. Relative use by elk was best explained by incorporating an interaction between diel period and predicted risky places across all seasons. Elk utilized risky places more in times of nutritional deficit associated with high energetic demands of the third trimester pregnancy and lactation and when forage quality was best, during spring and monsoon season. Particularly, use of risky places increased at less risky times in areas with more established wolf presence, suggesting use of risky places varied relative to exposure to Mexican wolves. These behaviors highlight the importance of temporal avoidance when predators and prey are highly mobile and largely overlap in space. Our research suggests temporally responding to predictable and relatively static environmental characteristics associated with encounter and kill rates may better balance energetic trade-offs than anticipating changes in wolf activity or spatially avoiding areas with higher wolf presence. Thus, elk appear to be more willing to take chances and mitigate cursorial predation risk with a more immediate, reactive approach and make proactive trade-offs during the seasons they can best increase fitness.

Arizona, New Mexico↗
USGS2025

Bears avoid residential neighborhoods in response to the experimental reduction of anthropogenic attractants

Introduction: Urbanization is an extreme form of land use alteration, with human development driving changes in the distribution of resources available to wildlife. Some large carnivores have learned to exploit anthropogenic food resources in urban development, resulting in human-carnivore conflict that can have detrimental impacts to people and carnivores, as exemplified by American black bears. Management agencies commonly promote the use of bear-resistant garbage containers for reducing conflicts, but little is known about the actual behavioral responses of bears to this intervention. Methods: To understand whether black bears alter their behavior in response to changes in residential waste management, we investigated patterns of bear behavior in Durango, Colorado, where anthropogenic attractants were experimentally manipulated. Using location data from collared black bears, we modeled resource selection and movement in response to areas that had received bear-resistant garbage containers compared to those that did not. Results: Bears avoided residential areas where garbage availability had been reduced, and this avoidance response increased over subsequent years, potentially suggesting that bears were learning from the management intervention. Bear movement rates, however, were not notably affected by the garbage reduction. Discussion: Our findings highlight the importance of reducing the availability of anthropogenic attractants for changing bear behavior and reducing risk of urban human-bear conflict, and that these responses can strengthen over time as bears learn from the management intervention.

Colorado↗
USGS2025

Rare milkvetch (Astragalus) persistence at a utility-scale solar energy facility in the Mojave Desert

Utility-scale solar energy (USSE) development is driving the projected growth in global renewable energy capacity but comes with environmental tradeoffs. New, alternative construction methods are promoted to minimize impacts to soils, vegetation, and hydrology; however, the disturbance created by these methods requires further investigation. We evaluated the population of a rare annual species, threecorner milkvetch ( Astragalus geyeri var. triquetrus ), at the Gemini Solar Project in the Mojave Desert, USA, two years after construction. Gemini was required to minimize disturbance in the threecorner milkvetch habitat, providing a unique opportunity to study the plant population and life history characteristics of a rare plant species under novel construction methods. Our objectives were to compare plant population characteristics of threecorner milkvetch inside and outside the Gemini footprint and in different photovoltaic (PV) panel microsites (interspace, panel dripline, under panel). We hypothesized that 1) threecorner milkvetch would have lower survival, reproduction, and growth, and a later phenology, inside compared to outside the facility, and 2) that these negative effects on plant demography and phenology would intensify with increasing proximity to photovoltaic panels in the solar array due to an increasing effect of disturbance and reduction of light and water availability. The results of this 1-year study during a favorable year of rainfall demonstrate the persistence of a rare Mojave annual plant species within an altered environment at a USSE facility. We found that threecorner milkvetch had an earlier phenology, grew larger, and had a higher fecundity at Gemini compared to plants off-site. Survivorship between the two populations, however, was not significantly different. Although growth and reproductive metrics were not correlated with distance to panel, minimal threecorner milkvetch emergence occurred directly under the PV panels and along their driplines, indicating a potential loss of suitable habitat if this pattern becomes more widespread in space or through time. Novel construction techniques for USSE could be considered moving forward to minimize impact on aboveground vegetation and maintain viable seed banks. The results of this study can assist land managers in making decisions about USSE development as the demand grows.

Nevada↗
USGS2026

Impacts of dams on river herring populations through their native range: What’s left?

Introduction: River herring (alewife, Alosa pseudoharengus , and blueback herring, Alosa aestivalis ) are native along the East Coast of North America. These fish are culturally important and provide critical ecosystem linkages between marine and freshwater habitats. Due to overfishing, and habitat loss (through degradation and damming), river herring populations are at historical lows across their native range. In the last 200 years, dams and other impoundments have reduced access to spawning habitat for these and other anadromous fish. Methods: To assess the theoretical coast-wide spawning potential for river herring, we quantified historically accessible spawning habitat (pre-dam) in coastal freshwater rivers using physical river characteristics (width and gradient). To assess the impact of dams on spawning habitat, we used a dams database to segment river reaches. This allowed us to characterize spawning habitat upstream and downstream of dams. River-specific population models were then used to estimate the number of potential spawners for each species, based on habitat estimates and life history parameters. We investigated three scenarios: no dams, favorable dam passage, and no dam passage. We use these simulations to compare the theoretical spawning potential for river herring prior to and after dam construction coastwide. Results: We estimated that 52% of alewife and 51% of blueback herring habitat is located upstream of dams throughout the East Coast of North America. This results in a theoretical loss of ~880 million alewife and ~100 million blueback herring potential spawners due to dams, reducing both the ecological connection and fishery potential of these species. Discussion: Even with the best-case “current” scenario for fish passage, we observed marginal increases in spawner abundance. These results highlight the relatively small theoretical influence current passage structures may have on restoring river herring to their historical abundances compared to dam removal. Our sensitivity analyses demonstrate that upstream passage to access additional habitat is only advantageous when effective juvenile and adult downstream passage are in place.

East Coast of North America↗
USGS2026

Mass mortality of avian migrants in New Mexico, USA, that coincided with an extreme weather event

Many birds are migratory, and this life history strategy allows for maximized access to seasonally abundant resources and favorable climates. However, migration exposes birds to threats and stressors, resulting in high mortality during migration. Anthropogenic landscape alterations and climate change have intensified threats, and mass mortality events linked to extreme weather are more common in recent decades. Documenting mass mortality is critical for predicting future occurrences and implementing effective conservation. Here, we describe a mortality event that occurred throughout New Mexico, USA in fall 2020. Carcasses began appearing in the region in mid-August, during a period of extreme heat and drought. Following an extreme cold weather event on September 8–9 th , the number of carcasses increased dramatically and expanded throughout the state. In total, we collected 628 carcasses comprising 58 species within Doña Ana and Otero Counties in New Mexico. Necropsy determined emaciation was the cause of death for 74.6% of carcasses. Live birds captured during the period of peak mortality (n = 223) were in similarly poor condition. This event provides a striking example of how multiple types of extreme stressors, in this case widespread drought and unseasonal cold, coincided with a mortality event, indicating a possible synergistic relationship between these factors and the mass mortality. Mortality events are likely to increase in frequency with intensifying climate change. Establishment of networks of biologists and researchers could improve our ability to identify and communicate developing mortality events, organize data collection, and improve understanding of the causes and consequences of mortality.

New Mexico↗
USGS2026

Non-native invasive beetle alters structure of a riparian bird community in a biodiversity hotspot

A serious emerging threat to southern California riparian ecosystems is the invasive shot hole borer ( Euwallacea spp.; SHB), a non-native beetle that cultivates a pathogenic fungus that kills trees of 66 reproductive host species. We examined the response of the bird community at the Tijuana River, California, to a massive SHB infestation in 2015 using data from a Monitoring Avian Productivity and Survivorship (MAPS) station operated during 7 pre-infestation (2009-15) and 7 post-infestation (2017-23) years. Species richness did not change between pre- and immediate (2017-18) post-SHB periods, but average annual adult captures declined by 27%. Among the species making up ≥ 5% of the total individuals caught in any one year (n=15), abundance declined by up to 76% in 10 species, including those most abundant at the station (Bushtit ( Psaltriparus minimus ), Song Sparrow ( Melospiza melodia ), Common Yellowthroat ( Geothlypis trichas ), Orange-crowned Warbler ( Leiothlypis celata ), and Wilson’s Warbler ( Cardellina pusilla )). Mean annual abundance increased slightly for the endangered Least Bell’s Vireo ( Vireo bellii pusillus ) and Northern Yellow Warbler ( Setophaga aestiva ) and doubled for House Finch ( Haemorhous mexicanus ) and Western Warbling-Vireo ( V. swainsoni ). We compared species trends at the Tijuana River to those at a nearby uninfested MAPS station on the Santa Margarita River to isolate the effect of SHB from other factors influencing annual abundance. The contribution of SHB to changes in abundance post-SHB was high (63-80%) for 7 declining species, moderate (22-45%) for 4 species, and weakly to moderately positive (18-40%) for 3 species. By 2019, the SHB infestation at the Tijuana River had abated and canopy cover was recovering through resprouting of mature willows ( Salix spp.) and seedling establishment. Bird abundance tracked this regrowth, with all of the species strongly affected by SHB increasing between 2019-23. The rapid recovery of the Tijuana River habitat and the associated response by the bird community are encouraging signs that the threat of the invasive shot hole borer to regional biodiversity may not be as great as originally anticipated.

California↗
USGS2026

Tracking Pacific salmon migrations with a prototype eDNA autosampler

Pacific salmon ( Oncorhynchus spp.) are keystone species that support commercial and recreational fisheries and play a significant role in Indigenous cultures. As a keystone species, they are commonly monitored to assess population metrics and adult and juvenile migration. Environmental DNA (eDNA) has been successfully applied to salmon monitoring, but these efforts have relied on manually collected samples which can limit temporal resolution and increase field effort. Here, we evaluated a prototype autonomous eDNA sampler for fine-scale tracking of adult salmon migrations in the Lake Washington Ship Canal (LWSC) in Washington state, USA. The autosampler was deployed approximately 3 km upstream of the Ballard Locks, where returning adult salmon are counted daily, for 4 months during the adult salmon return in 2022, and it collected eDNA samples twice daily (day and night) onto self-preserving filters. We tested eDNA samples for Chinook Salmon ( Oncorhynchus tshawytscha ), Sockeye Salmon ( O. nerka ) and Coho Salmon ( O. kisutch ) and results were compared with daily adult counts at the Ballard Locks. eDNA detection lagged visual counts by approximately 5 days for Sockeye and Coho salmon and approximately 23 days for Chinook Salmon. The extensive time lag in eDNA detection for Chinook Salmon was likely due to a thermal barrier, delaying their migration through the LWSC. We found no clear effect of day versus night sampling on eDNA detection probability. Two additional experiments were performed: one to assess eDNA degradation on used self-preserving filters stored in the autosampler and another to assess whether our 3 L system flush volume was sufficient to prevent residual eDNA from being carried over from one sample to the next. We found no apparent eDNA degradation but potential for sample-to-sample carry over at this flush volume. Our study highlights the need to consider strategic placement of the autosampler intake to optimize eDNA capture and testing of flush volumes to minimize sample-to-sample carryover. Autonomous eDNA sampling provided efficient, high-frequency, and fine-scale surveillance of salmon migrations and offers a scalable approach for a wide variety of monitoring applications.

Washington↗
USGS2026

Quantifying Chinook Salmon habitat across flow regimes: High resolution modeling in Oregon’s Willamette River basin

The Santiam and McKenzie River basins of western Oregon provide critical habitat for federally listed Upper Willamette River Spring Chinook salmon ( Oncorhynchus tshawytscha ). Streamflows in each basin are regulated in part by high-head multi-purpose dams; however, quantitative linkages between regulated streamflows and downstream habitat for juvenile and adult Chinook salmon remain limited. This study integrates high-resolution topo-bathymetric lidar, two-dimensional hydraulic models, and novel detailed sediment distribution models to evaluate habitat across a range of flows for over 400 river km. Results suggest that habitat quantity for two juvenile life stages (fry and parr) differs in response to streamflow; fry habitat appears to be relatively insensitive to streamflow, except in the downstream-most reaches of each river, while parr habitat generally increases from low to moderate flows, yet decreases at higher flows. Spawning habitat is largely inversely related to streamflow and is primarily limited by suitable substrate availability, likely reflecting sediment retention effects of upstream dams. Additionally, streamflow thresholds were identified where redd desiccation risk increases significantly with declining streamflow. These findings provide managers with spatially explicit tools to evaluate flow management tradeoffs during critical rearing and spawning periods and provide insights into habitat dynamics in large, regulated rivers. This work demonstrates how high-resolution modeling can support quantification of habitat at the landscape level.

Oregon↗