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At least 1,765 records · Page 98Linked to original sources

USGS2018

Multistate models of bigheaded carps in the Illinois River reveal spatial dynamics of invasive species

Knowledge of the spatial distributions and dispersal characteristics of invasive species is necessary for managing the spread of highly mobile species, such as invasive bigheaded carps (Bighead Carp [ Hypophthalmichthys nobilis ] and Silver Carp [ H. molitrix ]). Management of invasive bigheaded carps in the Illinois River has focused on using human-made barriers and harvest to limit dispersal towards the Laurentian Great Lakes. Acoustic telemetry data were used to parameterize multistate models to examine the spatial dynamics of bigheaded carps in the Illinois River to (1) evaluate the effects of existing dams on movement, (2) identify how individuals distribute among pools, and (3) gauge the effects of reductions in movement towards the invasion front. Multistate models estimated that movement was generally less likely among upper river pools (Starved Rock, Marseilles, and Dresden Island) than the lower river (La Grange and Peoria) which matched the pattern of gated versus wicket style dams. Simulations using estimated movement probabilities indicated that Bighead Carp accumulate in La Grange Pool while Silver Carp accumulate in Alton Pool. Fewer Bighead Carp reached the upper river compared to Silver Carp during simulations. Reducing upstream movement probabilities (e.g., reduced propagule pressure) by ≥ 75% into any of the upper river pools could reduce upper river abundance with similar results regardless of location. Given bigheaded carp reproduction in the upper Illinois River is presently limited, reduced movement towards the invasion front coupled with removal of individuals reaching these areas could limit potential future dispersal towards the Great Lakes.

Laurentian Great Lakes↗

USGS2023

Contemporary distribution of non-native Chinook salmon (Oncorhynchus tshawytscha) in South America

Chinook salmon represent one of the most successful salmonid introductions in South America, and today multiple naturalized populations exist across Patagonia. Here, we present an updated regional distribution of Chinook salmon that includes new records of occurrences collected between 2006 and 2022. We found a significant range expansion in terms of occurrences for adult (18 new basins; 2,854,108 km 2 ) and adult spawners or juvenile (12 new basins; 53,262 km 2 ) salmon extending both to the north and south of the previously known colonized range in South America. This range expansion (38% of the area considering only occurrences indicating reproduction via adult spawners or juvenile salmon) included major basins draining to both the Pacific Ocean and Atlantic Ocean coasts of the continent. Adult Chinook salmon are currently reported from 48 large basins (33.62°–54.97° S) covering a total drainage area of 3,047,197 km 2 . The observed expansion we document here has been likely driven by the dispersal of straying adults from historically naturalized populations. Our findings provide evidence that the invasion of Chinook salmon in South America is ongoing and updated information relevant to the management of this invasive and socio-ecologically important fish.

Biological Invasions↗

USGS2022

Speciation with gene flow in a narrow endemic West Virginia cave salamander (Gyrinophilus subterraneus)

Due to their limited geographic distributions and specialized ecologies, cave species are often highly endemic and can be especially vulnerable to habitat degradation within and surrounding the cave systems they inhabit. We investigated the evolutionary history of the West Virginia Spring Salamander ( Gyrinophilus subterraneus) , estimated the population trend from historic and current survey data, and assessed the current potential for water quality threats to the cave habitat. Our genomic data (mtDNA sequence and ddRADseq-derived SNPs) reveal two, distinct evolutionary lineages within General Davis Cave corresponding to G. subterraneus and its widely distributed sister species, Gyrinophilus porphyriticus , that are also differentiable based on morphological traits. Genomic models of evolutionary history strongly support asymmetric and continuous gene flow between the two lineages, and hybrid classification analyses identify only parental and first generation cross (F1) progeny. Collectively, these results point to a rare case of sympatric speciation occurring within the cave, leading to strong support for continuing to recognize G. subterraneus as a distinct and unique species. Due to its specialized habitat requirements, the complete distribution of G. subterraneus is unresolved, but using survey data in its type locality (and currently the only known occupied site), we find that the population within General Davis Cave has possibly declined over the last 45 years. Finally, our measures of cave and surface stream water quality did not reveal evidence of water quality impairment and provide important baselines for future monitoring. In addition, our unexpected finding of a hybrid zone and partial reproductive isolation between G. subterraneus and G. porphyriticus warrants further attention to better understand the evolutionary and conservation implications of occasional hybridization between the species.

West Virginia↗

USGS2024

Genetic structure of restored Brook Trout populations in the Southern Appalachian Mountains indicates successful reintroductions

Wildlife reintroduction is an important conservation tool for threatened species, yet identifying appropriate source populations poses a challenge. In particular, the possibility of outbreeding depression is cited as a constraint limiting the range of candidate source populations for translocation. When multiple source lineages are mixed during reintroduction, genetic monitoring is necessary to evaluate whether sources contribute equally to subsequent generations and whether they are interbreeding as expected. Moreover, statistical analysis of genetic data should account for complex life histories that might affect the timescale of admixture and genetic drift. Here, we use samples collected over a 23-year period and a stochastic age-structured model to analyze the genetic mixing process in reintroduced Brook Trout ( Salvelinus fontinalis ) populations in the Southern Appalachians. Each restored population was seeded with two to three source populations. Previous research inferred reproductive isolation between source populations leading to a proposal of splitting the species into multiple taxa. In contrast, we found patterns of ancestry that were consistent with random mating and no advantage for one source lineage over any other. Brook Trout from different source streams are mixing as expected in the restoration sites. This result does not support the hypothesis that Brook Trout in the Southern Appalachian Mountains includes several distinct species. Mixing different sources from the same watershed seems to be an effective way to increase genetic diversity of reintroduced populations while minimizing risk to source populations.

North Carolina, Tennessee↗

USGS2006

Lake whitefish and lake herring population structure and niche in ten south-central Ontario lakes

This study compares simple fish communities of ten oligotrophic lakes in south-central Ontario. Species densities and population size structure vary significantly among these lake communities depending on fish species present beyond the littoral zone. Lake whitefish are fewer and larger in the presence of lake herring than in their absence. Diet analysis indicates that lake whitefish shift from feeding on both plankton and benthic prey when lake herring are absent to a primarily benthic feeding niche in the presence of lake herring. When benthic round whitefish are present, lake whitefish size and density decline and they move lower in the lake compared to round whitefish. Burbot are also fewer and larger in lakes with lake herring than in lakes without herring. Burbot, in turn, appear to influence the population structure of benthic coregonine species. Lower densities of benthic lake whitefish and round whitefish are found in lakes containing large benthic burbot than in lakes with either small burbot or where burbot are absent. Predation on the pelagic larvae of burbot and lake whitefish by planktivorous lake herring alters the size and age structure of these populations. As life history theory predicts, those species with poor larval survival appear to adopt a bet-hedging life history strategy of long-lived individuals as a reproductive reserve.

Environmental Biology of Fishes↗

USGS2009

Threatened fishes of the world: Moapa coriacea Hubbs and Miller, 1948 (cyprinidae)

Moapa dace. Conservation status : Endangered (U.S. Department of the Interior 1967 ), Critically Endangered, IUCN (Gimenez 1996 ). Identification : Small embedded scales, narrow caudal peduncle and a bright black spot at the base of deeply forked tail. Pharyngeal teeth (0,5–4,0) hooked but with a grinding surface. Adults 50 to 120 mm total length. Drawing adapted from La Rivers ( 1962 ). Distribution : Endemic to the upper Muddy River system, Clark County, Nevada where the river originates from over 20 thermal springs. Prior to 1995 Moapa dace occupied 9.5 stream km including the upper Muddy River and spring-fed tributaries (U.S. Fish and Wildlife Service 1995 ). Distribution has contracted to 2 km (unpublished data) since the 1995 invasion of blue tilapia, Oreochromis aurea . Abundance : In 1994 the population was about 3,800, but after tilapia invasion dropped below 1,600 (Scoppettone et al. 1998 ) where it has remained (unpublished data). Habitat and ecology : Omnivorous but tends toward carnivory. Feed primarily on drift in areas adjacent to fast water 26–32°C. Reproduction : Occurs year round in spring-fed tributaries to the Muddy River in water temperature of 30–32°C (Scoppettone et al. 1992 ). Threats : Nonnative species (Scoppettone 1993 ; Scoppettone et al. 1998 ) and ground-water pumping (Mayer and Congdon 2008 ). Conservation actions : Moapa Valley National Wildlife Refuge was established in the upper Muddy River for the protection and perpetuation of Moapa dace. Barrier installation and chemical removal of blue tilapia downstream of refuge habitat provides 2 km of stream without tilapia. Conservation recommendations : Eliminate tilapia from the Muddy River system and control or eliminate other nonnative species. Protect spring discharge from excessive water withdrawal. Remarks : Given a high priority for recovery by the U.S. Government.

Environmental Biology of Fishes↗

USGS2012

Tradeoffs between homing and habitat quality for spawning site selection by hatchery-origin Chinook salmon

Spawning site selection by female salmon is based on complex and poorly understood tradeoffs between the homing instinct and the availability of appropriate habitat for successful reproduction. Previous studies have shown that hatchery-origin Chinook salmon ( Oncorhynchus tshawytscha ) released from different acclimation sites return with varying degrees of fidelity to these areas. To investigate the possibility that homing fidelity is associated with aquatic habitat conditions, we quantified physical habitat throughout 165 km in the upper Yakima River basin (Washington, USA) and mapped redd and carcass locations from 2004 to 2008. Principal components analysis identified differences in substrate, cover, stream width, and gradient among reaches surrounding acclimation sites, and canonical correspondence analysis revealed that these differences in habitat characteristics were associated with spatial patterns of spawning ( p < 0.01). These analyses indicated that female salmon may forego spawning near their acclimation area if the surrounding habitat is unsuitable. Evaluating the spatial context of acclimation areas in relation to surrounding habitat may provide essential information for effectively managing supplementation programs and prioritizing restoration actions.

Washington↗

USGS2013

Fluvial rainbow trout contribute to the colonization of steelhead ( Oncorhynchus mykiss ) in a small stream

Life history polymorphisms provide ecological and genetic diversity important to the long term persistence of species responding to stochastic environments. Oncorhynchus mykiss have complex and overlapping life history strategies that are also sympatric with hatchery populations. Passive integrated transponder (PIT) tags and parentage analysis were used to identify the life history, origin (hatchery or wild) and reproductive success of migratory rainbow/steelhead for two brood years after barriers were removed from a small stream. The fluvial rainbow trout provided a source of wild genotypes to the colonizing population boosting the number of successful spawners. Significantly more parr offspring were produced by anadromous parents than expected in brood year 2005, whereas significantly more parr offspring were produced by fluvial parents than expected in brood year 2006. Although hatchery steelhead were prevalent in the Methow Basin, they produced only 2 parr and no returning adults in Beaver Creek. On average, individual wild steelhead produced more parr offspring than the fluvial or hatchery groups. Yet, the offspring that returned as adult steelhead were from parents that produced few parr offspring, indicating that high production of parr offspring may not be related to greater returns of adult offspring. These data in combination with other studies of sympatric life histories of O. mykiss indicate that fluvial rainbow trout are important to the conservation and recovery of steelhead and should be included in the management and recovery efforts.

Washington↗

USGS2009

Wintering area DDE source to migratory white-faced ibis revealed by satellite telemetry and prey sampling

Locations of contaminant exposure for nesting migratory species are difficult to fully understand because of possible additional sources encountered during migration or on the wintering grounds. A portion of the migratory white-faced ibis (Plegadis chihi) nesting at Carson Lake, Nevada continues to be exposed to dichloro-diphenyldichloro-ethylene (DDE) with no change, which is unusual, observed in egg concentrations between 1985 and 2000. About 45-63% of the earliest nesting segment shows reduced reproductive success correlated with elevated egg concentrations of >4 ??g/g wet weight (ww). Local prey (primarily earthworms) near nests contained little DDE so we tracked the migration and wintering movements of 20 adult males during 2000-2004 to determine the possible source. At various wintering sites, we found a correlation (r 2 = 0.518, P = 0.0125, N = 11) between DDE in earthworm composites and DDE in blood plasma of white-faced ibis wintering there, although the plasma was collected on their breeding grounds soon after arrival. The main source of DDE was wintering areas in the Mexicali Valley of Baja California Norte, Mexico, and probably the adjacent Imperial Valley, California, USA. This unusual continuing DDE problem for white-faced ibis is associated with: the long-term persistence in soil of DDE; the earthworms' ability to bioconcentrate DDE from soil; the proclivity of white-faced ibis to feed on earthworms in agricultural fields; the species's extreme sensitivity to DDE in their eggs; and perhaps its life history strategy of being a "capital breeder". We suggest surveying and sampling white-faced ibis eggs at nesting colonies, especially at Carson Lake, to monitor the continuing influence of DDE.

Ecotoxicology↗

USGS2009

Polychlorinated biphenyls, dioxins, furans, and organochlorine pesticides in spotted sandpiper eggs from the upper Hudson River basin, New York

In 2004, spotted sandpipers ( Actitis macularia ) were studied on the Hudson River near Fort Edward south to New Baltimore, NY and on two river drainages that flow into the Hudson River. Concentrations of 28 organochlorine pesticides, 160 polychlorinated biphenyl (PCB) congeners, and 17 dioxin and furan (PCDD-F) congeners were quantified in eggs collected on and off the Hudson River. The pattern of organochlorine pesticides and PCDD-F congeners did not differ significantly between eggs collected on and off the Hudson River. In contrast, the pattern of PCB congeners differed significantly between the Hudson River and other rivers. Total PCBs were significantly greater in eggs from the Hudson River (geometric mean = 9.1 μg PCBs/g wet weight) than from the other two rivers (0.6 and 0.6 μg PCBs/g wet weight). Seven of 35 (20%) eggs exceeded 20 μg PCBs/g wet weight, the estimated threshold for reduced hatching in tree swallows ( Tachycineta bicolor ) and some raptor species; the maximum concentration was 72.3 μg PCBs/g wet weight. Models that predicted nest survival and egg success (the proportion of eggs hatching in a clutch if at least one egg hatched) as functions of contaminant levels were poorly distinguished from models that presumed no such associations. While small sample size could have contributed to the inability to distinguish among contaminant and no toxicant models, we cannot rule out the possibility that contaminant concentrations on the Hudson River were not sufficiently high to demonstrate a relationship between contaminant concentrations and reproductive success.

New York↗

USGS2016

Estimating the effects of 17α-ethinylestradiol on stochastic population growth rate of fathead minnows: a population synthesis of empirically derived vital rates

Urban freshwater streams in arid climates are wastewater effluent dominated ecosystems particularly impacted by bioactive chemicals including steroid estrogens that disrupt vertebrate reproduction. However, more understanding of the population and ecological consequences of exposure to wastewater effluent is needed. We used empirically derived vital rate estimates from a mesocosm study to develop a stochastic stage-structured population model and evaluated the effect of 17α-ethinylestradiol (EE2), the estrogen in human contraceptive pills, on fathead minnow Pimephales promelas stochastic population growth rate. Tested EE2 concentrations ranged from 3.2 to 10.9 ng L −1 and produced stochastic population growth rates (λ S ) below 1 at the lowest concentration, indicating potential for population decline. Declines in λ S compared to controls were evident in treatments that were lethal to adult males despite statistically insignificant effects on egg production and juvenile recruitment. In fact, results indicated that λ S was most sensitive to the survival of juveniles and female egg production. More broadly, our results document that population model results may differ even when empirically derived estimates of vital rates are similar among experimental treatments, and demonstrate how population models integrate and project the effects of stressors throughout the life cycle. Thus, stochastic population models can more effectively evaluate the ecological consequences of experimentally derived vital rates.

Ecotoxicology↗

USGS2020

Wetland water-management may influence mercury bioaccumulation in songbirds and ducks at a mercury hotspot

Mercury is a persistent, biomagnifying contaminant that can cause negative behavioral, immunological, and reproductive effects in wildlife and human populations. We examined the role of wetland water-management on mercury bioaccumulation in songbirds and ducks at Kellys Slough National Wildlife Refuge Complex, near Grand Forks, North Dakota USA. We assessed mercury concentrations in blood of wetland-foraging songbirds (80 common yellowthroats [ Geothlypis trichas ] and 14 Nelson’s sparrows [ Ammospiza nelsoni ]) and eggs of upland-nesting ducks (28 gadwall [ Mareca strepera ], 19 blue-winged teal [ Spatula discors ], and 13 northern shoveler [ S. clypeta ]) across four wetland water-management classifications. Nelson’s sparrow blood mercury concentrations were elevated (mean: 1.00 µg/g ww; 95% CL: 0.76–1.31) and similar to those reported 6 years previously. Mercury in songbird blood and duck eggs varied among wetland water-management classifications. Songbirds and ducks had 67% and 49% lower mercury concentrations, respectively, when occupying wetlands that were drawn down with water flow compared to individuals occupying isolated-depressional wetlands with no outflow. Additionally, songbirds within impounded and partially drawn-down wetland units with water flow had mercury concentrations that were 26–28% lower, respectively, than individuals within isolated-depressional wetlands with no outflow. Our results confirm that mercury concentrations in songbirds at Kellys Slough continue to be elevated and suggest that water-management could be an important tool for wetland managers to reduce bioaccumulation of mercury in birds.

North Dakota↗

USGS2021

Mercury exposure of tidal marsh songbirds in the northeastern United States and its association with nest survival

The biogeochemistry of tidal marsh sediments facilitates the transformation of mercury (Hg) into the biologically available form methylmercury (MeHg), resulting in elevated Hg exposures to tidal marsh wildlife. Saltmarsh and Acadian Nelson’s sparrows ( Ammospiza caudacutua and A. nelsoni subvirgatus , respectively) exclusively inhabit tidal marshes, potentially experiencing elevated risk to Hg exposure, and have experienced range-wide population declines. To characterize spatial and temporal variation of Hg exposure in these species, we sampled total mercury (THg) in blood collected from 9 populations spanning 560 km of coastline, including individuals resampled within and among years. Using concurrent nesting studies, we tested whether THg was correlated with nest survival probabilities, an index of fecundity. Blood THg ranged from 0.074–3.373 µg/g ww across 170 samples from 127 individuals. We detected high spatial variability in Hg exposure, observing differences of more than 45-fold across all individuals and 8-fold in mean blood THg among all study plots, including 4-fold between study plots within 4 km. Intraindividual changes in blood Hg exposure did not vary systematically in time but were considerable, varying by up to 2-fold within and among years. Controlling for both species differences and maximum water level, the dominant driver of fecundity in this system, nest survival probability decreased by 10% across the full range of female blood THg concentrations observed. We conclude that Hg has the potential to impair songbird reproduction, potentially exacerbating known climate-change driven population declines from sea-level rise in saltmarsh and Acadian Nelson’s sparrows.

Connecticut, Maine, New Hampshire, New Jersey↗

USGS2006

Trace element concentrations and bioindicator responses in tree swallows from northwestern Minnesota

Extremely high concentrations of cadmium (3.5 μ g/g dry wgt.) and elevated concentrations of chromium (>10 μ g/g dry wgt.) and mercury (1.6 μ g/g dry wgt.) were reported in waterbird tissues at Agassiz National Wildlife Refuge in northwestern Minnesota in 1994. Tree swallows ( Tachycineta bicolor) were studied during 1998–2001 at three drainages into the Refuge, two pools on the Refuge, and at a nearby reference location to document whether high levels of contaminants were still present, and if so to quantify the source and severity of the contamination. Trace elements were measured in tree swallow eggs, livers, and diet. Reproductive success and bioindicator responses were monitored. In 2000, water was drawn down on Agassiz Pool, one of the main pools on the Refuge. This presented an opportunity to evaluate the response of trace element concentrations in the diet and tissues of tree swallows after reflooding. High concentrations of trace elements were not detected in swallow tissues, nor were there differences among locations. Less than 20% of swallow samples had detectable concentrations of cadmium or chromium. Mercury concentrations were low and averaged <0.25 μ g/g dry wgt. in swallow tissues. Trace elements, including mercury, did not increase in tree swallows following the 2000 drawdown at Agassiz Pool. Hatching success and survival of nestlings to 12 days-of-age for tree swallows on the Refuge were similar to the national average and consistent with background trace element concentrations. Bioindicator measurements were within the normal ranges as well.

Minnesota↗

USGS2008

Murres, capelin and ocean climate: Inter-annual associations across a decadal shift

To ensure energy demands for reproduction are met, it is essential that marine birds breed during periods of peak food availability. We examined associations of the breeding chronology of common murres (Uria aalge) with the timing of the inshore arrival of their primary prey, capelin (Mallotus villosus) from 1980 to 2006 across a period of pervasive change in the Northwest Atlantic ecosystem. We also assessed the influence of ocean temperature and the North Atlantic Oscillation (NAO; an index of winter climate and oceanography) on these interactions. We found a lagged linear relationship between variations in murre breeding chronology and the timing of capelin arrival in the previous year. On a decadal level, we found a non-linear threshold relationship between ocean temperature and the timing of capelin arrival and murre breeding. Centennially anomalous cold water temperatures in 1991 generated a marked shift in the timing of capelin spawning inshore and murre breeding, delaying both by more than 2 weeks. By the mid-1990s, ocean temperatures returned to pre-perturbation levels, whereas the temporal breeding responses of capelin and murres were delayed for a decade or more. Oceanographic conditions (temperature, NAO) were poor predictors of the timing of capelin arrival inshore in the current year compared to the previous one. Our findings suggest that knowledge of the timing of capelin availability in the previous year provides a robust cue for the long-lived murres, allowing them to achieve temporal overlap between breeding and peak capelin availability. ?? Springer Science+Business Media B.V. 2008.

Environmental Monitoring and Assessment↗

USGS2009

Mercury contamination in three species of anuran amphibians from the Cache Creek watershed, California, USA

Fish and wildlife may bioaccumulate mercury (Hg) to levels that adversely affect reproduction, growth, and survival. Sources of Hg within the Cache Creek Watershed in northern California have been identified, and concentrations of Hg in invertebrates and fish have been documented. However, bioaccumulation of Hg by amphibians has not been evaluated. In this study, adult and juvenile American bullfrogs ( Lithobates catesbeianus ) and foothill yellow-legged frogs ( Rana boylii ), adult Northern Pacific treefrogs ( Pseudacris regilla ), and larval bullfrogs were collected and analyzed for total Hg. One or more species of amphibians from 40% of the 35 sites had mean Hg concentrations greater than the US Environmental Protection Agency’s tissue residue criterion for fish (0.3 μg/g). Of the bullfrog tissues analyzed, the liver had the highest concentrations of both total Hg and methyl mercury. Total Hg in carcasses of bullfrogs was highly correlated with total Hg in leg muscle, the tissue most often consumed by humans.

California↗

USGS2011

Selenium in aquatic biota inhabiting agricultural drains in the Salton Sea Basin, California

Resource managers are concerned that water conservation practices in irrigated farmlands along the southern border of the Salton Sea, Imperial County, California, could increase selenium concentrations in agricultural drainwater and harm the desert pupfish ( Cyprinodon macularius ), a federally protected endangered species. As part of a broader attempt to address this concern, we conducted a 3-year investigation to collect baseline information on selenium concentrations in seven agricultural drains inhabited by pupfish. We collected water, sediment, selected aquatic food-chain taxa (particulate organic detritus, filamentous algae, net plankton, and midge [Chironomidae] larvae), and two poeciliid fishes (western mosquitofish Gambusia affinis and sailfin molly Poecilia latipinna ) for selenium determinations. The two fish species served as ecological surrogates for pupfish, which we were not permitted to sacrifice. Dissolved selenium ranged from 0.70 to 32.8 μg/L, with selenate as the major constituent. Total selenium concentrations in other environmental matrices varied widely among drains, with one drain (Trifolium 18) exhibiting especially high concentrations in detritus, 5.98–58.0 μg Se/g; midge larvae, 12.7–50.6 μg Se/g; mosquitofish, 13.2–20.2 μg Se/g; and mollies, 12.8–30.4 μg Se/g (all tissue concentrations are based on dry weights). Although toxic thresholds for selenium in fishes from the Salton Sea are still poorly understood, available evidence suggests that ambient concentrations of this element may not be sufficiently elevated to adversely affect reproductive success and survival in selenium-tolerant poeciliids and pupfish.

Environmental Monitoring and Assessment↗

USGS2025

Tree swallow (Tachycineta bicolor) demographics and metal(loid) concentrations in egg contents from the Kootenai River basin, Montana nest box colonies

Selenium (Se) levels in water have been increasing in Lake Koocanusa and the Kootenai River below Libby Dam in Montana due to coal mining in the drainage basin of the Elk River, British Columbia. Aquatic monitoring of Se is ongoing to assess potential effects; however, exposure to terrestrial, aquatic-dependent wildlife has not been investigated. Tree swallows are a targeted receptor for evaluation of potential Se-related effects as this species is a mid-level consumer with aquatic-terrestrial food web linkages, is sensitive to Se, and reliably uses nest boxes. The goals of this project were to identify tree swallow demographics and metal(loid) concentrations to assess potential species and ecosystem-level effects within the Kootenai River basin study area. During 2022 and 2023, a total of 98 nest boxes were monitored across ~ 120 km of shoreline; 60 eggs were collected. Egg metal(loid) concentrations, including Se, were below levels identified to cause reproductive effects in avian species. However, nest box occupancy increased with distance from the US/Canada border ( P < 0.001; R 2 = 0.83), and Se concentrations were significantly higher ( P = 0.014) in 2023 than 2022 (3.2 (3.0–3.4) and 2.8 (2.6–3.1), respectively; geometric mean, 95% CI; mg/kg, dw). With ongoing mining operations in the drainage basin of the Elk River, these results suggest that long-term monitoring of tree swallows will support assessment of spatiotemporal metal(loid) trends. Additional data, including tree swallow foraging patterns, will allow evaluation of differences in nest box occupancy and metal(loid) concentrations in the Kootenai River basin.

Montana↗