ABSTRACT Climate change has elevated the intensity and frequency of droughts, affecting wildlife population dynamics. In arid environments, drought can have severe consequences for life history parameters, such as survival and emigration, especially for species of conservation concern. We analyzed a 34‐year dataset in a mark‐recapture framework to estimate demographic parameters for Mohave ground squirrels (Xerospermophilus mohavensis), a threatened species confronted with climate change and drought. Specifically, we examined the influence of individual‐, geographic‐, and environmental‐related variables on survival, emigration, emigration fidelity (i.e., the probability that an animal that has moved away from the study site will remain away), capture probability, recapture probability, and number of unmarked animals, the latter of which allowed us to estimate population size. We captured 1404 squirrels at four study sites. Overall, male squirrels had lower survival and higher emigration rates than did female squirrels, and juveniles had lower survival than adults. Emigration was lower at the highest‐elevation study site than at other sites. Survival of male squirrels increased with higher levels of vegetation greenness. At two of the four study sites, emigration of squirrels of both sexes decreased with higher levels of vegetation greenness. No variables influenced emigration fidelity or number of unmarked animals. Initial capture probabilities were lower for males than for females, and for juveniles than for adults, whereas recapture probabilities were lower for adults than for juveniles. Population size fluctuated over time with several peaks during the study separated by periods of low numbers, which occasionally fell to zero at each site. By the end of the study, adult population size at the two sites with the longest‐term monitoring was 70% lower than its peak early in the study. Demography of Mohave ground squirrels was characterized by a large amount of variation, leaving them highly vulnerable to additional stress from climate change. Our findings suggest that conservation management actions, such as prioritizing sites with consistently high levels of vegetation greenness, protecting contiguous areas of suitable habitat, and enhancing emigration success of squirrels, may promote the long‐term viability of this species as climate changes. They also illustrate how long‐term population monitoring can be used to support management for other conservation‐relevant species affected by climate change and drought.

Accurate information underpins successful ecological science and management. Cryptic species, those that are difficult to differentiate, pose challenges to reliable collection of taxon-specific information. Blackbirds, including tricolored blackbirds ( Agelaius tricolor ), a cryptic species of high conservation concern, and red-winged blackbirds ( Agelaius phoeniceus ), an abundant congener, are sometimes killed by wind turbines. We used publicly available survey records to evaluate rates at which blackbirds were reported dead at wind energy facilities in California, USA. We then used genetic species identification of carcasses found to estimate true rates of discovery and of misidentification. Of 329 blackbird fatalities in survey records, most were identified as red-winged ( n  = 149), “unidentified” ( n  = 90), or Brewer's ( Euphagus cyanocephalus ; n  = 70); only 13 were identified as tricolored. We also genetically analyzed samples from 40 blackbirds. Of 14 carcasses identified in the field to species, two, including one tricolored, were incorrectly called Brewer's blackbirds (14% misidentification rate). Of the 26 birds called “unidentified blackbird” in the field, 17 (65%) were tricolored, leading to a 19× underestimation of true fatality rate. The state-wide population of tricolored blackbirds is < 1% the size of that of red-winged blackbirds. A large proportion of blackbirds found dead were actually tricoloreds, indicating that fatality rates of this state threatened species may be substantially underestimated. The potential for misidentification or nonidentification may create perverse incentives that undermine conservation and have consequences for on-the-ground management, mitigation, and operations of high-priority infrastructure.

Conservation breeding programs support biodiversity by supplementing wild populations with captive-bred individuals to bolster population size and genetic diversity. Successful reproduction and long-term viability of offspring, which may depend on early-life traits such as egg size and fertility, are fundamental components of conservation breeding programs but are rarely systematically assessed. We analyzed data from 499 Gymnogyps californianus (California Condor) eggs laid at The World Center for Birds of Prey in Boise, Idaho, USA in 1995-2024 to test the effects of individual-specific traits (age, rearing, inbreeding coefficient, seasonal laying order, and prior-year double laying), pair-specific traits (relatedness and length of pairing), and year effects on fertility and egg weight (a proxy for egg size). Bayesian mixed models suggested that egg weight varied strongly among but not within individual females. Egg weight decreased with seasonal laying order, was independent of prior-year reproductive output, and peaked when females were middle-aged (similar to 10-25 yr). Egg fertility was high (78%) and showed a similar female age quadratic effect. Egg weight had a positive effect on fertility. We found no effect of any other variables on egg weight or fertility. Our findings highlight senescence and individual variation as factors shaping early-life traits in a captive-bred species. Individuals breeding in captivity have access to unlimited resources, suggesting that variation in egg size is more likely driven by intrinsic female traits than by environmental factors. The genetic and developmental traits that we tested did not mediate this effect on egg size, pointing to other female characteristics as drivers. Optimizing such traits through individualized management could become a valuable tool in conservation breeding and have lasting effects on reproductive success. This study provides a foundation for more systematic, evidence-based decision-making to inform management practices across conservation breeding programs. Conservation breeding programs support biodiversity by supplementing wild populations with captive-bred individuals. Their impact depends on successful reproduction in captivity, which can be influenced by factors, such as egg size and fertility.We analyzed data from 499 Gymnogyps californianus (California Condor) eggs laid in captivity from 1995 to 2024 to identify what drives variation in egg weight and fertility.Egg weight varied strongly among individual females and decreased from the first to the second egg laid within a season. Both egg weight and fertility peaked when females were middle-aged (similar to 10-25 yr). Fertility increased with egg weight.Our findings highlight age and individual variation as key drivers of egg weight and fertility, suggesting variation is likely influenced by internal female characteristics.Optimizing egg weight and fertility through captive breeding practices could improve success of the conservation breeding program for this critically endangered species. Los programas de reproducci & oacute;n para la conservaci & oacute;n apoyan la biodiversidad al complementar las poblaciones silvestres con individuos criados en cautiverio para reforzar el tama & ntilde;o poblacional y la diversidad gen & eacute;tica. La reproducci & oacute;n exitosa y la viabilidad a largo plazo de la descendencia, que pueden depender de rasgos de vida tempranos como el tama & ntilde;o del huevo y la fertilidad, son componentes fundamentales de los programas de reproducci & oacute;n para la conservaci & oacute;n, pero rara vez se eval & uacute;an de manera sistem & aacute;tica. Analizamos datos de 499 huevos de Gymnogyps californianus puestos en el Centro Mundial para Aves de Presa en Boise, Idaho, EUA, entre 1995 y 2024, para evaluar los efectos de rasgos espec & iacute;ficos del individuo (edad, tipo de crianza, coeficiente de endogamia, orden de puesta estacional y doble puesta en el a & ntilde;o previo), rasgos espec & iacute;ficos de la pareja (grado de parentesco y duraci & oacute;n del emparejamiento) y efectos interanuales sobre la fertilidad y el peso del huevo (como proxy del tama & ntilde;o del huevo). Los modelos mixtos bayesianos sugirieron que el peso del huevo vari & oacute; fuertemente entre hembras, pero no dentro de una misma hembra. El peso del huevo disminuy & oacute; con el orden de puesta estacional, fue independiente del desempe & ntilde;o reproductivo del a & ntilde;o previo y alcanz & oacute; su m & aacute;ximo cuando las hembras se encontraban en edad intermedia (similar to 10-25 a & ntilde;os). La fertilidad de los huevos fue alta (78%) y mostr & oacute; un efecto cuadr & aacute;tico similar de la edad de la hembra. El peso del huevo tuvo un efecto positivo sobre la fertilidad. No encontramos efecto de ninguna otra variable sobre el peso del huevo o la fertilidad. Nuestros resultados destacan a la senescencia y a la variaci & oacute;n individual como factores que moldean los rasgos tempranos en una especie criada en cautiverio. Los individuos que se reproducen en cautiverio tienen acceso a recursos ilimitados, lo que sugiere que la variaci & oacute;n en el tama & ntilde;o del huevo est & aacute; m & aacute;s probablemente determinada por rasgos intr & iacute;nsecos de las hembras que por factores ambientales. Los rasgos gen & eacute;ticos y de desarrollo que evaluamos no mediaron este efecto sobre el tama & ntilde;o del huevo, lo que apunta a otras caracter & iacute;sticas de las hembras como los factores determinantes. La optimizaci & oacute;n de estos rasgos mediante un manejo individualizado podr & iacute;a convertirse en una herramienta valiosa en la reproducci & oacute;n para la conservaci & oacute;n y tener efectos duraderos sobre el & eacute;xito reproductivo. Este estudio proporciona una base para una toma de decisiones m & aacute;s sistem & aacute;tica y basada en evidencia que oriente las pr & aacute;cticas de manejo en programas de reproducci & oacute;n para la conservaci & oacute;n.

Solar energy can produce climate-related and conservation benefits to species and ecosystems, but it can also incur costs to wildlife. Because future solar development is expected to occur on lands with high value for animal occupancy and movement, research on behavioral responses of wildlife to solar facilities can inform management of conservation lands. We asked how ranging behavior, habitat use, and disease risk of desert kit foxes (Vulpes macrotis arsipus) responded to development and operation of three conglomerations of industrial-scale solar facilities in southern California, two in the Sonoran Desert ("Riverside-West" and "Riverside-East") and one in the Mojave Desert ("ISEGS-Stateline"). Home ranges were smaller for foxes in the Riverside-East population (x = 9.01 km2, n =10 foxes), with less solar development, than in the Riverside-West (x = 22.37 km2, n = 3 foxes) or ISEGS-Stateline (x =17.21 km2, n = 8 foxes) populations, with more development. Home ranges of most foxes overlapped solar facilities that were under construction or fully operational, with up to 47% of home-range area, 65% of locations, and 84% of days inside solar facilities. Fox use of habitat was most distinct at Riverside-East and more similar at Riverside-West and ISEGS-Stateline; at a fine scale, foxes used most parts of ISEGS-Stateline. Canine distemper virus, which has previously been documented in kit foxes near solar development, was not prevalent. Our results show that the desert kit foxes we tracked ranged into solar facilities and used habitats there extensively, even daily, both during and post-construction. Thus, solar energy development may be compatible with conservation for this subspecies. Active management of solar facilities that increases their accessibility to wildlife may produce further conservation benefits for desert kit foxes.

Lead exposure has been documented in a multitude of bird and mammal species but less frequently in reptiles. Of the studies that have evaluated lead concentrations in reptiles, few have focused on snakes. We analyzed lead concentrations in liver and two types of bone from 24 gophersnakes (Pituophis catenifer; Pc) and 12 Great Basin rattlesnakes (Crotalus oreganus lutosus; Col) found dead along roads in the Morley Nelson Snake River Birds of Prey National Conservation Area in southwestern Idaho, U.S.A from 2018 to 2021. Because this area has been heavily impacted by both military and recreational activity, we also quantified lead concentrations in the soil near where the dead snakes were found. All soil samples had detectable lead (median: 12.53 µg/g; range: 0.07–16.77). Within individuals of both species, dry weight lead concentrations in liver generally were lower than those in bone (n samples < LOQ Liver: 9 of 13 (Pc), 9 of 10 (Col) (only a subset of individuals were in good enough condition to provide liver samples); Bone: 0 of 24 (Pc), 3 of 12 (Col). We did not detect any differences in lead concentrations between the species for either tissue type, nor between bone from the front (anterior) or back (posterior) of the snake skeleton. Additionally, we did not detect any correlation between lead concentration in soil collected at the roadkill sites and the tissue in the snakes. These data provide baseline information for lead exposure of two snake species in southwestern Idaho and demonstrate how lead is present in higher trophic levels within this ecosystem.

Lead (Pb) threatens wildlife and humans through neurological, cardiovascular, and renal damage. Conventional tissue Pb assessment relies on costly wet-lab methods such as inductively coupled plasma mass spectrometry (ICP-MS). Monochromatic X-ray fluorescence (MXRF) enables rapid, non-destructive, field-deployable Pb detection with lower detection limits than prior portable XRF systems. We evaluated the feasibility, calibration, attenuation correction, and ICP-MS agreement of a doubly curved crystal (DCC)-enhanced MXRF (X-ray Optical Systems, East Greenbush, NY) for bone Pb quantification in American black vultures (Coragyps atratus). Thirty-eight bird bones were analyzed ex vivo (n = 19 femurs; n = 19 tarsometatarsi[TMT]) using an HD Mobile XRF (1-mm spot; Mo anode; silicon drift detector; 200s). Calibration used Pb-doped plaster phantoms (0-100 ppm) with polymethyl methacrylate soft-tissue equivalents (0-5 mm). Spectra (10.0-13.6 keV) were fit with a Gaussian Pb-peak on a smooth background and Compton sideband normalization. Matched samples were quantified by ICP-MS. Agreement was assessed by ordinary least squares (OLS) regression, Pearson r, Passing-Bablok, intraclass correlation coefficient (ICC; two-way, absolute), reduced major axis (RMA) regression, and Bland-Altman analysis. Detection limits were obtained using blank-and-slope calibration and 30 repeated measurements on two bones. Signal attenuated exponentially, limiting reliable quantification beyond ∼3 mm soft tissue. Calibration was linear (counts vs. ppm: R2 = 0.996; phantom nominal vs. MXRF: R2 = 0.994). MXRF agreed closely with ICP-MS (femur r = 0.959, ICC = 0.933; TMT r = 0.962, ICC = 0.953). Bland-Altman mean biases were small (femur: -1.73 μg/g; TMT: -0.42 μg/g) without proportional bias. Passing-Bablok slopes approached unity (≈0.86-0.96) with small intercepts. Practical DLs were 1.79 μg/g(femur) and 0.80 μg/g(TMT) and are the relevant benchmarks for biological measurement; the calibration-derived instrumental DL of 0.03 μg/g at 200 s is an idealized zero-matrix value. This DCC-based MXRF delivered rapid, non-destructive bone Pb estimates concordant with ICP-MS and low DLs. Attenuation correction and fixed geometry support ex vivo Pb surveillance, carcass triage, and program evaluation in birds, with extension to other species, including humans.

The golden eagle (Aquila chrysaetos) is an apex predator across its Holarctic range. Although chromosome-level reference genome assemblies are available for two of the six golden eagle subspecies (European and Japanese), current assemblies for the North American subspecies (A. c. canadensis) were generated using short-read sequencing technology, limiting completeness, contiguity, and accuracy. Here we present a chromosome-length de novo genome assembly for a male A. c. canadensis as part of the California Conservation Genomics Project. We used Pacific Biosciences HiFi reads and Omni-C chromatin-proximity sequencing to produce a high-quality assembly consistent with the standard California Conservation Genomics Project reference genome protocol. Our assembly spans 1.28 Gbp and comprises 316 scaffolds with a scaffold N50 of 47.3 Mbp, a contig N50 of 30.3 Mbp, and a benchmarking universal single-copy ortholog completeness score of 97.4%. This reference genome assembly offers a valuable resource for delineating genomic variation and assessing conservation needs in golden eagle populations across California and its North American range more broadly.

Niche partitioning allows similar species to coexist while minimizing competitive interactions. Much work on this theme evaluates behavioral observations. However, movement data with transmitters provide another means to quantify behavioral differences among species. We focused on four movement characteristics to explore differences in flight behavior of two resident species of vultures, the White-headed Vulture (Trigonoceps occipitalis) and the White-backed Vulture (Gyps africanus), in and around Gorongosa National Park in central Mozambique. We found, although there was substantial similarity in flight behavior of the two species, that White-headed Vultures tended to fly at lower altitudes and slower speeds, and to initiate flight earlier in the day than did White-backed Vultures. White-headed Vultures were also slightly more likely to be active throughout the day than were White-backed Vultures. Due to lower wing loading, White-headed Vultures require less intense thermal uplift for flight than do White-backed Vultures, enabling lower altitude flight and slower speeds. This may facilitate their search for smaller carcasses and even prey. These results highlight both the ecological differences between these two critically endangered species and also how they partition available niches.

Floating photovoltaic solar energy presents an opportunity to mitigate climate change and spare land for other uses, including conservation. However, understanding of the effects of floating photovoltaics (FPVs) on aquatic ecosystems is currently limited. In fact, so far, only a few studies have empirically tested how wildlife responds to FPV deployment and operation. Here we present five key considerations spanning both the direct and indirect effects that FPVs can have on waterbirds and the possible ways waterbirds can interact with and directly affect FPV sites. We examine several aspects of FPVs and their deployment and operation, providing insight into FPV–waterbird dynamics, potential mitigation strategies, and viable concessions for conservation as water surfaces become a more widespread recipient environment for renewable energy. This Perspective leverages waterbirds to establish a conceptual foundation for studying wildlife interactions with floating photovoltaics (FPVs), highlighting five key considerations to guide future research on FPV–wildlife interactions.

Aquila chrysaetos (Golden Eagles) are long-lived top predators, vulnerable to a variety of threats. There is increasing concern about the declining population in coastal southern California, which has largely coincided with habitat loss due to urbanization of the region. This Mediterranean-type ecosystem is also experiencing more prolonged and intense droughts, which can reduce the abundance of key prey species, such as jackrabbits (Lepus californicus) and ground squirrels (Otospermophilus beecheyi). However, the impact of drought on A. chrysaetos is poorly understood. Here, we used high-resolution GPS tracking data to calculate eagle home ranges and hypothesized that home range size would be influenced by drought such that home ranges would be larger to meet their resource needs with worsening drought severity. Fifty individuals were captured over 7 breeding seasons, spanning the time both during and after a historic drought. We also compared space use for different stages of the breeding season throughout each year. Golden Eagle home ranges increased by 77% during extreme drought compared to wetter conditions. Drought-breaking rainfall corresponded with much smaller home ranges compared to home range sizes during drought years. As drought is projected to be more prolonged and frequent in this region with climate change, this may result in increasingly large home range sizes at the same time as eagles are facing ongoing habitat loss and fragmentation from various land use changes. Our results suggest that the frequent and severe drought that is projected for this region could lead to lowered nesting density and increase the risk of further population decline.

Effective conservation of migratory birds requires gathering of information about their population trends, often acquired using migratory bird counts. These schemes ideally operate at migratory bottlenecks, through which a significant portion of the counted migratory populations is funneled. Yet it is rare to validate the conservation value of the data from these counts. Here we perform this validation using GPS tracking data collected from two migratory species during their movement over two count schemes: the globally endangered steppe eagle counted in Eilat, Israel, and the black kite, counted in Batumi, Georgia. We use tracking data to answer two questions: which populations are counted and what affects the probability that a given individual will be counted. Our results illustrate variability in the effectiveness of these two migratory bird counting schemes. Considering the goal of estimating population trends, we show that Eilat does not represent a good location for understanding population trends of steppe eagles, while Batumi appears to provide better information on demographic trends of black kites. We further present differences in annual and individual variability, evidence regarding the breeding area origins of the counted populations and effects of environmental factors on the raptors' routes and, consequently, on the probabilities of being counted. Beyond the direct implications of our results, this study provides an example of using telemetry data to parameterize inference from bird counts. Further coupling of migratory bird count data and GPS data can improve our understanding of migration ecology and the conservation of migratory species.

Life-history theory posits that species evolve strategies to maximize lifetime fitness in response to environmental variability. For example, many species evolve complex social systems with adults that do not hold territories, a class of individuals labeled floaters. Populations of Haliaeetus leucocephalus (Bald Eagle) and Aquila chrysaetos (Golden Eagle) often have floaters whose behavior and demography are poorly understood. To differentiate between different behavioral states, we applied a random forest algorithm to GPS movement metrics generated from 43 adult H. leucocephalus and 94 adult A. chrysaetos, tracked over 164 and 274 breeding seasons, respectively. Using these movement metrics, we accurately predicted behavioral states within breeding seasons and individual eagles, providing an objective approach for state classification. For H. leucocephalus, we documented 101 (62%) territorial and 63 (38%) floater seasons. Within seasons when H. leucocephalus were territorial, 66% nested and 34% did not nest. For A. chrysaetos, we identified 178 (65%) territorial and 96 (35%) floater seasons. Within seasons when A. chrysaetos were territorial, 68% nested and 32% did not nest. Across individual eagles (as opposed to eagle seasons), 49% of monitored H. leucocephalus and 58% of A. chrysaetos were exclusively territorial, 37% and 33% were exclusively floaters, and 19% and 14% showed both behaviors. Sex was not a strong predictor, although more male A. chrysaetos were floaters than females, hinting at underlying demographic or behavioral differences between sexes. Importantly, our findings emphasize that a substantial and dynamic portion of the adult eagle population exists in the floater state. Understanding the behavioral states of long-lived raptors can contribute to accurate assessment of their population dynamics as well as conservation and management. Recognizing the prevalence of floaters in population assessments, for eagles and other long-lived species, likely will have critical implications for monitoring and conservation strategies.

All terrestrial species interact with the airspace.1 The principles derived from the study of those interactions, i.e., from the field of aeroecology,2 are most often used to model species movements (e.g., Miller et al.3 and Nourani et al.4). Despite this, they are almost never used to understand species distributions,5 an issue fundamental to ecology, conservation, and management.6,7,8 We used resource selection functions and species distribution models to (1) show that aeroecological principles are a driver of seasonally variable distributions for critically endangered California condors (Gymnogyps californianus) and (2) predict range expansion for this heavily managed and rapidly growing population. Condors used thermal updraft either directly in proportion to, or less frequently than, predicted by its availability. However, during winter, when thermals are weak, they used orographic (deflected) updraft more than would be expected, suggesting that condor distribution was limited by the availability of predictable orographic updraft. Furthermore, resource selection functions for condors always performed better with than without aeroecological predictors. Aeroecological species distribution models predicted that habitat selected most strongly by condors would vary seasonally with changes in the weather, from 1.7%-5.0% (winter) to 6.6%-11.1% (spring/autumn) of California and Oregon. Explaining seasonal variation in condor distribution with aeroecological principles led to insights contrary to conventional wisdom that interannual movement of soaring avian scavengers responds to transiting of their food, domesticated and wild ungulates. Incorporating aeroecological principles into models of species distributions can lead to better understanding of animal movement and distributions and provide information with substantial consequence to endangered species management.

BACKGROUND:Lead (Pb) contamination in wildlife remains a critical environmental concern, particularly for scavenger species, which are at high risk due to ingestion of lead-contaminated carrion. Portable XRF (pXRF) systems can be useful to evaluate lead concentration of wild animals in vivo. However, the accuracy of these systems has never been validated for living birds. METHODS:We evaluated differences in the quantification of lead in the tarsometatarsus (TMT) and femur bones of 19 wild-caught black vultures (Coragyps atratus) by portable (pXRF) and benchtop X-ray fluorescence (XRF) systems with validation against inductively-coupled plasma mass spectrometry (ICP-MS). RESULTS:We found a strong correlation between benchtop XRF and ICP-MS (R² = 0.92-0.95), and lower correlation between pXRF and ICP-MS (R² = 0.62-0.67), primarily because pXRF systematically underestimated lead concentrations. When compared to ICP-MS, Intraclass Correlation Coefficients (ICC) further confirmed better performance of benchtop XRF in measuring femur and TMT lead (ICC = 0.959-0.968) compared to pXRF (ICC = 0.739-0.742). pXRF in vivo TMT lead concentrations were highly correlated (R² = 0.85) to ex vivo results with the same instrument, with the soft tissue on the living animal having minimal effect on the measurement. DISCUSSION:Although pXRF offers critical advantages in field applications, its limitations necessitate careful interpretation of results. Future research could improve pXRF optimization and extend this approach to other wildlife populations. This work contributes valuable data on lead exposure in vultures and illustrates a mechanism by which lead exposure of birds can be evaluated in vivo in wild or captive populations.

Wind is increasingly used as a renewable source of energy worldwide. However, harvesting wind energy can have negative consequences for biodiversity. In this Review, we summarize the growth of onshore wind power, its impacts on species and ecosystems, and how those impacts are assessed and mitigated. Across the construction, operation and decommissioning stages, wind facilities are associated with wildlife fatality and behavioural change as well as alteration, loss and fragmentation of terrestrial and aerial habitat. These negative consequences can be mitigated by avoiding construction of wind turbines at sensitive sites, detecting and deterring wildlife, curtailing turbines to reduce fatalities, and replacing lost habitats. Uncertainty about wildlife populations and their demographic parameters, the rate and extent of build-out of onshore wind energy, and best practices for mitigation, as well as variability in regulatory requirements by country or region, all contribute to the difficulty of predicting the consequences of this technology for biodiversity. Scenario-based modelling that incorporates population- and community-level consequences to biodiversity from varying degrees of wind energy development — including the cumulative effects of multiple facilities — is key to addressing this uncertainty. This Review discusses the biodiversity effects of onshore wind energy generation (including changes to land and aerial habitats, altered wildlife behaviour and wildlife fatalities) and present and future opportunities to mitigate these impacts as the technology grows rapidly worldwide.

Avian fatalities caused by collisions with overhead power lines are an important conservation issue worldwide. Although mitigation strategies can help reduce mortalities, given their considerable cost and the vast scale of power line infrastructure, cost-effective action requires that these efforts be prioritised to areas with the highest potential risk to birds. To date, this risk assessment has usually been guided by potentially biased information on the location of recorded fatalities. Here we use 6 years of GPS-tracking data from endangered Tasmanian wedge-tailed eagles to develop an alternative approach to risk assessment: fine-scale spatial risk models based on behavioural analyses. We built and cross-validated a model that generates spatially explicit predictions of the probability that eagles would cross power lines at hazardous altitudes throughout the entire Tasmanian electricity distribution network. In our model, the probability of power line crossings was most strongly associated with the proportion of open habitat, forest edges, rural residential developments, wet forest and freshwater sources in the area surrounding the power lines. Cross-validation indicated that the model effectively predicted where Tasmanian wedge-tailed eagles cross power lines at low altitude. Model validation suggested our approach was a powerful predictor of the locations of power line collisions involving eagles. The locations of almost all (94%) confirmed eagle fatalities were in the half of the total Tasmanian power line area assigned the higher risk by the model, and 50% of incidents occurred in the 20% of the power line area estimated to be highest risk. Synthesis and applications. Our study illustrates a framework for using bird movement data to provide insights into avian behaviour and the risk they encounter around power line infrastructure. Electricity delivery industries can use these models to identify the electrical infrastructure that poses the highest risk to avian survival and prioritise mitigation efforts, thereby optimising the benefit of investments to reduce detrimental effects on biodiversity. Our model can inform pre-emptive mitigation across Tasmania's 20,310 km of distribution infrastructure to meet management targets aiming to reduce the negative effects of power lines on the Tasmanian wedge-tailed eagle.

ABSTRACT The Morley Nelson Snake River Birds of Prey National Conservation Area (NCA), in southwestern Idaho, USA supports a large population of breeding Prairie Falcons (Falco mexicanus). Abundance of Prairie Falcons in the NCA was previously monitored in 1976–1978 and 1990–1994. That research indicated maximum counts for each period in 1976 and 1992 and a possible population decline across that time span. We assessed the abundance and nesting success of Prairie Falcons in the NCA in 2002–2003 and 2019–2021, and we compared results to data from before 2000 to assess possible population change. Number of nesting pairs increased over 45 years from peak counts of 206, 193, and 217 in the 1970s, 1990s, and early 2000s, respectively, to 257 in 2021. Increases were not concentrated in one region, but widely distributed across the study area. Rates of nesting success in 2002–2003 and 2019–2021 averaged 57 ± 11.8% (SD) at 49.8 ± 3.3 nests observed each year and did not differ from pre-2000 rates. Finally, our analysis showed that in all 10 years in which a full census was conducted, a sampling approach to surveys would have been effective at estimating the number of falcons nesting within the NCA. Prairie Falcons are of conservation concern because of possible population declines in parts of their range. These results illustrate an area with apparently increasing numbers of this important species and highlight the importance of long-term surveys for tracking population fluctuations and the value of a national conservation area for providing raptor breeding habitat.

In 2023, an outbreak of highly pathogenic avian influenza occurred among critically endangered California condors (Gymnogyps californianus), and >21 died. We evaluated safety, immunogenicity, vaccination strategies, and correlates of antibody response of an influenza vaccine for poultry in black vultures (Coragyps atratus) and then California condors. We noted differences in antibody titers between vaccinated and unvaccinated birds (vultures p<0.004; condors p-<0.02) but no adverse effects of vaccination. All vaccinated vultures and 80% of vaccinated condors showed maximum measured antibody response within the published range associated with survival of vaccinated and virally challenged chickens. We noted weak evidence of higher antibody responses for birds given two 0.5-mL vaccines versus those given one 1-mL vaccine but no correlation between antibody titers and sex for either species or between antibody titers and bone lead concentrations in vultures. Our results prompted initiation of a vaccination program for condors that could reduce spread of this disease among highly threatened species.

A challenge facing bat conservation and wind energy development is how to maximize renewable energy production while minimizing impacts to bat populations. Reproductive-aged females are particularly important to dynamics and stability of bat populations due to their life history characteristics, but morphological sex identification methods have resulted in inaccurate reporting of sex ratios of fatalities at wind energy facilities. Our goal was to assess overall species-specific sex ratios of fatalities, and how those ratios varied by time and location. We used molecular techniques to determine the sex of 4445 carcasses of Brazilian free-tailed (Tadarida brasiliensis), evening (Nycticeius humeralis), hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), northern yellow (Lasiurus intermedius), silver-haired (Lasionycteris noctivagans), and southern yellow (Lasiurus ega) bats found during turbine searches at 20 wind energy facilities in ten states in the United States between 2009 and 2022. Species composition and number of years of data varied by site. Overall, there were more fatalities of females than males for silver-haired and southern yellow bats, but not the other species. Brazilian free-tailed bat sex ratios were female skewed in late summer, whereas female skew occurred during portions of spring and summer/fall for eastern red bats, hoary, and silver-haired bats, and in spring and late fall for evening bats. In addition, spatial patterns in sex ratios existed for eastern red and hoary bats. The observed spatial and temporal patterns of fatalities can help target fatality reductions strategies to locations and times of year that maximize the conservation benefit of those actions.

The Rocky Mountain Population (RMP) of trumpeter swans Cygnus buccinator (hereafter, swans) in North America includes breeders in the Greater Yellowstone Area (GYA) and other western states (together, United States segment) and western provinces of Canada (Canada segment). Conservation concern for the United States segment stems from its slow population growth and the resident nature of GYA swans, which intermingle with migrating Canada segment swans in wintering habitats. Thus, understanding variation in migratory behavior and habitat use by swans in the two population segments can inform how management actions may affect the RMP. We used telemetry data from 55 RMP swans captured in the western United States to understand their movements and habitat use. For 45 swans (60 swan-years) that spent the summer in the United States, distance traveled between breeding and wintering areas ranged from 0 km (i.e., no migration in 22% of swan-years) to 473 km, with an average of nonzero movements of 118 +/- 95 km (SD). Swans traveled farther distances when maximum temperatures were lower. For 10 swans (16 swan-years) that spent the summer in Canada, five appeared to molt but not to nest, and four appeared to nest in one or more years. Migration timing was similar for molting and nesting swans. All five molting swans and one nesting swan spent at least one previous summer in the GYA. Migratory connectivity of all birds was weaker in years when more swans migrated to Canada for the summer. During the breeding season, Canada swans used low-elevation lakes, but United States swans used high-elevation lakes. Both groups of swans increased use of crop fields outside of the breeding season. Our study shows interchange between the United States and Canada segments, a finding that challenges the efficacy of existing population designations. Furthermore, variation in movement behavior of GYA swans suggests possible actions, such as restoring winter habitats to increase swan distribution and migration, to support swan conservation.