Advances in fine-scale movement modeling of soaring birds can aid efforts to understand and resolve the impacts of anthropogenic activities on such birds. Soaring birds often rely on underlying terrain and low-altitude updrafts to govern their flights at rotor-swept altitudes (≤ 200 m above ground level), which puts them at risk of collision with wind turbines. We developed a data-driven Markov model at 1-s resolution that predicts the fine-scale flight behavior of golden eagles (Aquila chrysaetos) as a function of ecological covariates at the current location as well as those within an eagle's line of sight. We only considered ecological covariates that are readily available in real-time (ground elevation and wind conditions). Latent factors (age, sex, species, behavioral intent, migratory status) were intentionally left out of the model. We calibrated the model using golden eagle telemetry data collected in two different ecoregions of the United States. Given a starting location, the calibrated model simulates multiple stochastic 3D paths to produce a time-explicit and spatially explicit risk map of turbine collisions. We discovered an empirical relation between the rate of change of heading and the orographic updraft conditions within an eagle's line of sight. Our model performed most effectively when predicting predominantly-soaring flights at rotor-swept altitudes during wind conditions in which turbines are likely to be operational. The calibrated model could be used in concert with automated eagle detection and turbine curtailment technologies. Specifically, once an eagle is detected by those systems, our model could then provide accurate predictions of turbines the eagle is likely to interact with in the near term.

Due to attachment weight limitations, animals under 5g have remained a major methodological barrier in movement ecology, limiting tracking options for many small-bodied organisms. We developed and field-tested an ultra-light solar powered transmitter (BlūMorpho 0.058- 0.060g) designed to enable continuous, near real-time tracking using a broad, crowd sourced network. We validated the system on two North American hummingbird species during spring migration, demonstrating reliable detection, multi-week retention, broad spatial coverage (United States, Mexico and Canada), and long-distance migration paths including a 6,526km cumulative track. Our results highlight the ability to track the smallest of species across the full migratory range with fine-scale spatial resolution and high temporal resolution using the BlūMorpho transmitter. Importantly, we present the first migratory tracks known to exist on North American hummingbird species. ### Competing Interest Statement The authors have declared no competing interest.

Automated radio telemetry systems (ARTS) consisting of animal-borne radio transmitters and networks of fixed radio receivers are frequently used to continuously track wildlife movements over time. The low weight of available radio transmitters and the ability of these systems to collect data with high temporal resolution make ARTS an attractive alternative to other wildlife tracking technologies. However, the research questions that can be addressed with ARTS are often limited by the spatial accuracy of location data produced by the system. One of the primary methods used to produce location estimates with ARTS involves comparing the received signal strength (RSS) of radio transmissions detected by multiple receivers in a network. The accuracy of the resulting locations is highly dependent on the algorithm used to process the raw RSS data generated by the ARTS into location estimates. In this work, we have developed a grid search algorithm for producing location estimates from RSS data generated by networks of receivers. In an experiment conducted with a radio transmitter and receiver network, we demonstrate that the grid search method produces location estimates that are greater than 2 times more accurate than the commonly used method of multilateration. A simulation was developed to compare the accuracy of the two methods over a large range of receiver spacings and with varying levels of measurement noise in the system. The simulation showed that the grid search method and multilateration perform similarly for receiver networks with relatively close receivers; however, as the distance between receivers in the array increases, the mean error of location estimates increases much more rapidly for multilateration than for grid search. The improvement in spatial accuracy realized through the use of grid search enables the design of wildlife tracking studies utilizing ARTS to address research questions that were previously inaccessible.

Turbulence grounds aircraft and combating it in flight requires energy, yet volant wildlife fly effortlessly even on windy days. The nature of the interactions between soaring birds and transient turbulent gusts is not clear, especially when compared with our understanding of flight in larger and steadier airflows during thermal or dynamic soaring. We show that soaring golden eagles (Aquila chrysaetos) experienced short upward accelerations indicative of preferential engagement with strong and intermittent turbulent updrafts. The vertical accelerations reflect changes in lift that were as large as 25 standard deviations from the mean, or more than three times the acceleration of gravity, and so large as not to be consistent with gust mitigation or avoidance. These extreme events occurred in short bursts that mimic movement with turbulent vortices. The burst statistics and their symmetries approach those of turbulence toward longer timescales. On the shortest timescales, the bursts break the symmetry of small-scale turbulence in favor of upward accelerations that are more intermittent than turbulence. We introduce a simple nonlinear model that predicts the scale at which symmetry breaks and the stronger intermittency on the smaller scales. These findings suggest a ratcheting mechanism on turbulent gusts and constitute the first quantitative evidence in favor of turbulent gust harvesting by wildlife. An implications is that turbulence is so strong and pervasive as to make unsteady and nonlinear aerodynamics an intrinsic and beneficial aspect of both flapping and soaring flight in the atmospheric boundary layer - one that we need to incorporate in our understanding of the energetics of flight.

Flight calls are short vocalizations frequently associated with migratory behavior that may maintain group structure, signal individual identity, and facilitate intra- and interspecific communication. In this study, Magnolia Warbler (Setophaga magnolia) flight call characteristics varied significantly by season and recording location, but not age or sex, and an individual’s flight calls were significantly more similar to one another than to calls of other individuals. To determine if flight calls encode traits of the signaling individual during migration, we analyzed acoustic characteristics of the calls from the nocturnally migrating Magnolia Warbler. Specifically, we analyzed calls recorded from temporarily captured birds across the northeastern United States, including Appledore Island in Maine, Braddock Bay Bird Observatory in New York, and Powdermill Avian Research Center in Pennsylvania to quantify variation attributable to individual identity, sex, age, seasonality, and recording location. Overall, our findings suggest that Magnolia Warbler flight calls may show meaningful individual variation and exhibit previously undescribed spatiotemporal variation, providing a basis for future research.

Golden Eagles (Aquila chrysaetos) have a Holarctic distribution, but some details of that overall distribution are poorly understood, including parts of the range in eastern North America. Recent studies in the region suggest that Golden Eagles may be more widely distributed than previously recognized. For species specific conservation efforts to be effective, an understanding of the distribution of the species is essential. Thus, the goal of this study was to map the winter distribution of Golden Eagles in the eastern half of the USA. To accomplish this, we reviewed and compiled 11,981 Golden Eagle records from eight data sources, including literature and ornithology records, community science data, survey data, and telemetry data. We found that Golden Eagles were observed in winter in each of the 31 states that lie completely east of the 100th meridian and in 1244 of the 2045 counties (61%) in those states. The proportion of counties with records varied by physiographic province, with higher proportions in physiographic provinces with more rugged terrain and greater forest cover. Our study shows that Golden Eagles are more widely distributed during winter in eastern USA states than was previously recognized. This work provides an important foundation for future management and research at a time when threats to this species are expanding rapidly on the landscape.

One-second-processed three-dimensional position observations transmitted from an instrumented golden eagle were used to determine the detailed long-range flight behavior of the bird. Once elevated from the surface, the eagle systematically used atmospheric gravity waves, first to gain altitude, and then, in multiple sequential glides, to cover over 100 km with a minimum expenditure of its metabolic energy.

Turbulent winds and gusts fluctuate on a wide range of timescales from milliseconds to minutes and longer, a range that overlaps the timescales of avian flight behavior, yet the importance of turbulence to avian behavior is unclear. By combining wind speed data with the measured accelerations of a golden eagle (Aquila chrysaetos) flying in the wild, we find evidence in favor of a linear relationship between the eagle's accelerations and atmospheric turbulence for timescales between about 1/2 and 10 s. These timescales are comparable to those of typical eagle behaviors, corresponding to between about 1 and 25 wingbeats, and to those of turbulent gusts both larger than the eagle's wingspan and smaller than large-scale atmospheric phenomena such as convection cells. The eagle's accelerations exhibit power spectra and intermittent activity characteristic of turbulence and increase in proportion to the turbulence intensity. Intermittency results in accelerations that are occasionally several times stronger than gravity, which the eagle works against to stay aloft. These imprints of turbulence on the bird's movements need to be further explored to understand the energetics of birds and other volant life-forms, to improve our own methods of flying through ceaselessly turbulent environments, and to engage airborne wildlife as distributed probes of the changing conditions in the atmosphere.

Habitat selection studies are designed to generate predictions of species distributions or inference regarding general habitat associations and individual variation in habitat use. Such studies frequently involve either individually indexed locations gathered across limited spatial extents and analyzed using resource selection functions (RSFs) or spatially extensive locational data without individual resolution typically analyzed using species distribution models. Both analytical methodologies have certain desirable features, but analyses that combine individual- and population-level inference with flexible non-linear functions may provide improved predictions while accounting for individual variation. Here, we describe how RSFs can be fit using hierarchical generalized additive models (HGAMs) using widely available software, providing a means to explore individual variation in habitat associations and to generate species distribution maps. We used GPS tracking data from golden eagles Aquila chrysaetos from across eastern North America with four environmental predictors to generate monthly distribution models. We considered three model structures that assumed different amounts of individual variation in the functional relationship between predictors and habitat use and used k-fold cross-validation to compare model performance. Models accounting for individual variability in shape and smoothness of functional responses performed best. Eagles exhibited the least amount of individual variation in response to land cover variables during winter months, with most individuals more closely adhering to the population-level trend. During the summer months, eagles exhibited more substantial individual variation in shape and smoothness of the functional relationships, suggesting some need to account for individual variation in eagle habitat use for both inferential and predictive purposes, during this time of year. Because they allow users to blend flexible functions with random effects structures and are well-supported by a variety of software platforms, we believe that HGAMs provide a useful addition to the suite of analyses used for modeling habitat associations or predicting species distributions.

ABSTRACTWeather can shape movements of animals and alter their exposure to anthropogenic threats. Bald eagles (Haliaeetus leucocephalus) are increasingly at risk from collision with turbines used in onshore wind energy generation. In the midwestern United States, development of this energy source typically occurs in upland areas that bald eagles use only intermittently. Our objective was to determine the factors that cause wintering bald eagles to occupy riparian areas and riskier, upland areas. We tracked 20 bald eagles using telemetry in the Upper Midwest (MN, IA, MO, WI, IL, USA) during winter 2014–2015 and 2015–2016 and evaluated habitat use by eagles in response to variation in weather and time of year. Eagles used riparian areas more when wind speed and atmospheric pressure were low. Exclusive use of uplands was more frequent during weather systems with low pressure and high humidity and after long periods of cold weather. There was a non‐linear response to time of year (measured by days before migration) in the frequency of exclusive use of uplands or riparian areas. Probability of exclusive use of either landscape was generally constant within 95 days prior to migration. The probability of use of riparian areas, however, was markedly less during dates >100 days before migration. Our results suggest that eagles are most likely to be exposed to wind energy developments located in upland areas during low pressure systems, after long periods of cold weather, and several months before the onset of spring migration. This information helps to better understand the factors influencing bald eagle habitat use in winter and will be useful to managers and developers wishing to establish effective strategies to avoid, minimize, and mitigate take, and to survey for mortalities at wind energy developments. © 2020 The Wildlife Society.

Wildlife conservation is often improved by understanding the movement ecology of species and adapting management strategies to dynamic conditions associated with movement. Despite a remarkable recovery over the past 30 years, the establishment of self-sustaining populations of California Condors (Gymnogyps californianus) has been challenging in the human-dominated landscapes of southern California. Among these challenges are those imposed by condor ground-foraging behavior that exposes them to environmental contamination. These include lead poisoning from the ingestion of spent ammunition and micro-trash ingestion and, during takeoff and landing, collisions with human structures. We tracked 28 California Condors for 24 months with patagially mounted GPS telemetry units to investigate the characteristics of ground sites condors visited and to identify spatiotemporal trends that might aid in conservation of this critically endangered species. Ground sites occurred on a wide variety of land cover types, primarily on steep slopes, and those more frequently used were associated with open cover. Condors concentrated their visits to ground sites around a 3 h period near midday, and usage increased from winter to late summer. Our study is the first to use remotely sensed telemetry data to describe fine-scale ecological correlates of condor ground-foraging ecology and therefore has important relevance for ongoing conservation and management strategies for this species. The descriptions of ground sites we provide can be used to target conservation or management actions.

Wind turbines occur on every continent of the world. Although, many species of wildlife have been negatively affected by the construction of wind turbines, risk of negative effects on wildlife is not equal among wind facilities or among individual wind turbines. Because wildlife and industry select resources to maximize either biological fitness or economic return, we can estimate risk by overlaying models of resource selection for both.

Wind power is a fast-growing energy resource, but wind turbines can kill volant wildlife, and the flight behavior of obligate soaring birds can place them at risk of collision with these structures. We analyzed altitudinal data from GPS telemetry of critically endangered California Condors (Gymnogyps californianus) to assess the circumstances under which their flight behavior may place them at risk from collision with wind turbines. Condor flight behavior was strongly influenced by topography and land cover, and birds flew at lower altitudes and closer to the rotor-swept zone of wind turbines when over ridgelines and steep slopes and over forested and grassland cover types. Condor flight behavior was temporally predictable, and birds flew lower and closer to the rotor-swept zone during early morning and evening hours and during the winter months, when thermal updrafts were weakest. Although condors only occasionally flew at altitudes that placed them in the rotor-swept zone of turbines, they regularly flew near or within wind resource areas preferred by energy developers. Practitioners aiming to mitigate collision risk to this and other soaring bird species of conservation concern can consider the manner in which flight behavior varies temporally and in response to areas of high topographic relief and proximity to nocturnal roosting sites. By contrast, collision risk to large soaring birds from turbines should be relatively lower over flatter and less rugged areas and in habitat used during daytime soaring.

Behavior of young birds can have important consequences for population dynamics. We investigated the autumnal post-fledging movements of 3 White-tailed Sea Eagles (Haliacents albicilla) hatched in Kazakhstan. All 3 eagles traveled south, flying on average 25-108 km/d. Movement was nonrandom, with eagles generally traveling near mosaics of forest, open areas, and water, and rarely using areas with little vegetation. As the first study of movements of White-tailed Sea Eagles in arid Central Asia, this study provides insight into potential limiting factors and how these birds interact with their environment during long-distance movements.

Wind power is a fast-growing industry with broad potential to impact flying wildlife. Understanding these impacts is critical to developing effective strategies and recommendations for siting turbines and for mitigating impacts to animals. We tracked ~80 Golden Eagles Aquila chrysaetos in eastern North America with GPS-GSM telemetry systems. The fast data collection frequency we used allowed us to understand details of flight behavior and thus risk to birds from wind turbines along migration routes and on wintering grounds.

Wind power is a fast-growing industry with broad potential to impact flying wildlife. Understanding these impacts is critical to developing effective strategies and recommendations for siting turbines and for mitigating impacts to animals. We tracked ~80 Golden Eagles Aquila chrysaetos in eastern North America with GPS-GSM telemetry systems. The fast data collection frequency we used allowed us to understand details of flight behavior and thus risk to birds from wind turbines along migration routes and on wintering grounds.

ABSTRACT Lead poisoning is a threat to birds, particularly scavenging birds of prey. With the availability of portable lead‐testing kits, an increasing number of field researchers are testing wild‐caught birds, in situ , for lead poisoning. We describe guidelines for evaluation of lead toxicity in wild raptors by outlining field testing of blood‐lead concentrations, presenting criteria for removing a lead‐poisoned bird from the wild for treatment, and suggesting strategies for effective treatment of lead intoxicated raptors. Field testing of birds is most commonly accomplished via portable electrochemical analysis of blood; visual observation of condition alone may provide insufficient evidence upon which to make a decision about lead poisoning. Our intended audience is not only the avian research community, but also rehabilitation facilities that may receive apparently uninjured birds. Best practices suggest that birds whose blood‐lead levels are <40 μg/dL be released back to the wild as soon as possible after capture. The decision to release or treat birds with blood‐lead levels between 40 μg/dL and 60 μg/dL should be made based on the presence of clinical signs of poisoning and relevant biological characteristics (e.g., breeding status). Finally, birds with blood‐lead levels >60 μg/dL are potentially lethally poisoned and best served if removed from the wild for appropriate treatment at a licensed rehabilitation facility and later released. We present guidelines for decision‐making when treating lead poisoning of wild raptors. Future work based on experimental studies will clarify the role of lead poisoning for specific species and be important to refine these guidelines to improve effectiveness. © 2017 The Wildlife Society.

Lead poisoning of animals due to ingestion of fragments from lead-based ammunition in carcasses and offal of shot wildlife is acknowledged globally and raises great concerns about potential behavioral effects leading to increased mortality risks. Lead levels in blood were correlated with progress of the moose hunting season. Based on analyses of tracking data, we found that even sublethal lead concentrations in blood (25 ppb, wet weight), can likely negatively affect movement behavior (flight height and movement rate) of free-ranging scavenging Golden Eagles (Aquila chrysaetos). Lead levels in liver of recovered post-mortem analyzed eagles suggested that sublethal exposure increases the risk of mortality in eagles. Such adverse effects on animals are probably common worldwide and across species, where game hunting with lead-based ammunition is widespread. Our study highlights lead exposure as a considerably more serious threat to wildlife conservation than previously realized and suggests implementation of bans of lead ammunition for hunting.

Conserving wide-ranging animals requires knowledge about their year-round movements and resource use. Golden Eagles (Aquila chrysaetos) exhibit a wide range of movement patterns across North America. We combined tracking data from 571 Golden Eagles from multiple independent satellite-telemetry projects from North America to provide a comprehensive look at the magnitude and extent of these movements on a continental scale. We compared patterns of use relative to four alternative administrative and ecological mapping systems, namely Bird Conservation Regions (BCRs), U.S. administrative migratory bird flyways, Migratory Bird Joint Ventures, and Landscape Conservation Cooperatives. Our analyses suggested that eagles initially captured in eastern North America used space differently than those captured in western North America. Other groups of eagles that exhibited distinct patterns in space use included long-distance migrants from northern latitudes, and southwestern and Californian desert residents. There were also several groupings of eagles in the Intermountain West. Using this collaborative approach, we have identified large-scale movement patterns that may not have been possible with individual studies. These results will support landscape-scale conservation measures for Golden Eagles across North America.

Soaring birds can balance the energetic costs of movement by switching between flapping, soaring and gliding flight. Accelerometers can allow quantification of flight behavior and thus a context to interpret these energetic costs. However, models to interpret accelerometry data are still being developed, rarely trained with supervised datasets, and difficult to apply. We collected accelerometry data at 140Hz from a trained golden eagle (Aquila chrysaetos) whose flight we recorded with video that we used to characterize behavior. We applied two forms of supervised classifications, random forest (RF) models and K-nearest neighbor (KNN) models. The KNN model was substantially easier to implement than the RF approach but both were highly accurate in classifying basic behaviors such as flapping (85.5% and 83.6% accurate, respectively), soaring (92.8% and 87.6%) and sitting (84.1% and 88.9%) with overall accuracies of 86.6% and 92.3% respectively. More detailed classification schemes, with specific behaviors such as banking and straight flights were well classified only by the KNN model (91.24% accurate; RF = 61.64% accurate). The RF model maintained its accuracy of classifying basic behavior classification accuracy of basic behaviors at sampling frequencies as low as 10Hz, the KNN at sampling frequencies as low as 20Hz. Classification of accelerometer data collected from free ranging birds demonstrated a strong dependence of predicted behavior on the type of classification model used. Our analyses demonstrate the consequence of different approaches to classification of accelerometry data, the potential to optimize classification algorithms with validated flight behaviors to improve classification accuracy, ideal sampling frequencies for different classification algorithms, and a number of ways to improve commonly used analytical techniques and best practices for classification of accelerometry data.