In the USA, funding for rehabilitating Golden Eagles (Aquila chrysaetos) from injuries and diseases may serve to offset incidental take of the species as authorized by permit from the US Fish and Wildlife Service, e.g., for blade-strike fatalities at wind turbines. However, post-release survival of these eagles may differ from that of their wild conspecifics. Our objectives were to (1) estimate the survival rate of rehabilitated Golden Eagles tracked via satellite telemetry in western North America during their first post-release year; (2) compare the estimate to that of wild Golden Eagles; and (3) estimate how many rehabilitated individuals must be released such that one would be as likely to survive its first post-release year as a wild eagle would to survive any given year. During March 2013-June 2023, we tracked 27 Golden Eagles that had been admitted for rehabilitation when >= 1 yr (AFY) of age, mostly (>= 85.2%) due to anthropogenic factors; rehabilitation lasted 23-321 d (median = 125.0). Within 1 yr of release, 15 (55.6%) of the eagles died, nine (33.3%) remained alive, and fates of three (11.1%) were unknown (tracked 44 d, 134 d, and 294 d). The mean survival rate estimate from a multistate model was 0.31 (SD = 0.08), versus 0.87 (SD = 0.07) for wild AFY Golden Eagles. We estimated that 3.5 rehabilitated Golden Eagles must be released for one to be as likely to survive its first post-release year as a wild Golden Eagle would to survive any given year.

We describe the development of a custom 37 K Affymetrix Axiom myDesign single nucleotide polymorphism (SNP) array for a culturally and ecologically important apex predator, the golden eagle (Aquila chrysaetos). Using this SNP array, we performed population genomic analysis on 154 individuals of known natal localities and detected three genetic clusters that we designated as Taiga/High Arctic, Great Basin, and Rocky Mountains/Great Plains. Each of these clusters appears to display clinal variation within these geographic regions. After determining genetic structure, we performed an assignment test of 32 individuals, five of which were siblings of individuals used in the assessment of genetic structure, three had associated telemetry data, and the remaining individuals were of unknown natal locations. Using this array, four siblings were correctly assigned to the same geographic region as their sibling and the genetic assignment of the radio telemetered birds agreed with the expected movement patterns displayed by these individuals. For the remaining individuals, we were able to assign all but five individuals to one of the three genetic clusters. Our genetic assignments illustrates the utility of this SNP array to accurately assign most individuals to predesignated geographical regions. While further compiling genetic and other data types, we can increase the power of this tool for identifying those breeding populations that may need assistance due to anthropogenic stressors that negatively impact their population viability. The use of this genetic resource will help substantiate decisions by multiple conservation groups that seek to preserve the natural population structure of the golden eagle.

Birds exhibit flexible movement responses to environmental variation across the annual cycle, and those responses can provide insight into potential impacts that environmental changes may have on these species. To understand year‐round variation in space use by Ferruginous Hawks Buteo regalis, we tracked 12 birds breeding in southwestern Idaho, USA, using GPS telemetry collected over 207 bird‐months. Home‐range sizes of territorial adult hawks showed strong intra‐annual variation, being smallest from April to June and largest from July to October. In contrast, juvenile birds (< 2 years old) did not appear to hold territories and showed no detectable intra‐annual variation in ranging behaviour. Association with land‐cover types by territorial birds varied between breeding and non‐breeding months and was linked to home‐range size. Home‐range sizes of non‐territorial birds were larger than those of territorial birds, and that size did not vary across the year. Association with anthropogenic habitats (irrigated cropland habitats that can provide high rodent densities and increased foraging opportunities) was negatively associated with home‐range size in months of the non‐breeding season. Unexpectedly, the opposite was true in the months of the breeding season, such that use of croplands resulted in larger home‐ranges. Patterns in home‐range size were probably linked to intrinsic factors such as the timing of breeding and migratory behaviour, and to extrinsic factors such as prey availability associated with specific land‐cover types. These results have implications for our understanding of the response of Ferruginous Hawks and other similar species to predicted changes in land cover, and they suggest unexpected relationships between human activity and wildlife behaviour. Furthermore, because the birds we tracked used a large portion of western North America, they are probably relevant far beyond the small area where these individuals were trapped.

The Common Buzzard. By Sean Walls and Robert Kenward. 2020. T & AD Poyser, Bloomsbury Publishing Plc, 50 Bedford Square, London, WC1B 3DP, UK. 304 pp., 8 pp. color photographs (32 total photos), 66 figures, 5 maps, 27 black and white photos, 15 black and white illustrations, 4 appendices, and index. ISBN 978-1-47297208-8. Paperback, $50.00. After over thirty years of studying Common Buzzards (Buteo buteo) across England, Sean Walls and Robert Kenward compile their expertise and passion for the species in The Common Buzzard. This book summarizes the existing knowledge and understanding of Common Buzzard biology. Tying in information with findings and observations from their own studies, this book provides the reader with a comprehensive and engaging overview of the life history, ecology, and conservation of this European Buteo. We (the reviewers who have experience with the North American genus Buteo) admit to knowing little about the book’s specific species—the Common Buzzard—prior to having read it. At first we wondered if this made us good candidates to review this work; however, we both came to realize that we were among the authors’ target audience and, as North American raptor biologists who did not have preconceived notions of Common Buzzard biology, were well suited to speak to the success of the book’s intent and the clarity of its message. There are 29 species worldwide classified in the genus Buteo. In Europe, raptors from the genus Buteo are commonly called ‘‘buzzards,’’ while in North America, Buteos are referred to as ‘‘hawks.’’ Both terms are rather ambiguous and occasionally cause confusion, since they can occasionally refer to species outside of the genus Buteo. For example, worldwide there are birds commonly called ‘‘hawks’’ that are not classified as Buteos (e.g., Sharpshinned Hawk [Accipiter striatus]; Cooper’s Hawk [Accipiter cooperii]; Eurasian Sparrowhawk [Accipiter nisus]). Similarly, there are also birds commonly called ‘‘buzzards’’ not classified as Buteos (e.g., European Honey-Buzzard [Pernis apivorus]; Black-breasted Buzzard [Hamirostra melanosternon]). So while the terms ‘‘hawk’’ and ‘‘buzzard’’ can refer to raptors outside the genus Buteo, the terms are not used in common names of all raptors. Adding further to confusion between the two terms is that the term ‘‘buzzard’’ has long been a colloquialism for a North American vulture. Indeed, it is not a simple task to answer the question: What is a buzzard? Fortunately, this book reminds us that, no matter what word we use—‘‘hawk’’ or ‘‘buzzard’’ or otherwise— raptors are fascinating critters. As different as raptor species can be from each other, they are also similar in many ways. As such, what we learn about one species might have applications to another. Indeed, many of this book’s chapters, described below, will resonate with researchers studying other raptor species around the globe. From cover to cover, this book informs the reader about Common Buzzards in a logical way that addresses most aspects of their ecology. It begins with a discussion of evolutionary traits and taxonomy (Chapter 1: A Common Buzzard), and moves through topics such as hunting abilities and prey variety (Chapter 2: Prey, and Chapter 3: Hunting), habitat use including territoriality and nest defense (Chapter 4: Habitat use, and Chapter 5: Territoriality and nest defence), reproduction (Chapter 6: Courtship and nesting, and Chapter 7: Incubating and chick-rearing), movement (Chapter 8: Dispersal and migration), survival and demographics (Chapter 9: Longevity and survival, and Chapter 10: Common Buzzard populations), and finally concludes with a look at the history of human interactions with the species (Chapter 11: Our relationship with the Common Buzzard). One favorable aspect of this book that is likely to set it apart is the connection both authors have with its subject, the Common Buzzard. We realized soon after starting our reading that both Walls and Kenward have dedicated a great deal of their careers to studying the species. In particular, together they conducted a long-term telemetry study of Common Buzzard fledglings and followed them for multiple years after fledging. This research project was, no doubt, an incredible undertaking and contributed much to the knowledge of the species. Their understanding and enthusiasm for Common Buzzards shines through in the writing. The book includes many delightful lessons on raptor ecology in general, going beyond the limited topical scope suggested by the title. This too makes the book stand out not just as an excellent contribution to the Common Buzzard body of knowledge but to the general raptor research and conservation literature. Despite their obvious affinity for this species, we liked that the authors avoided using gushing language or hyperbole to describe it or compare it to other raptors. In fact, on occasion they did the opposite, describing Common Buzzards as a ‘‘base-line model hawk’’ (page 20) that is rather plain in appearance, small in stature, and relatively common. The authors let the information they provide and their respect and passion for the species invoke the reader’s interest in Common Buzzards, something that we (the reviewers) noticed and appreciated. Indeed, this book does a wonderful job illustrating that a species does

Anticoagulant rodenticides (ARs) are commonly used to control rodent pests. However, worldwide, their use is associated with secondary and tertiary poisoning of nontarget species, especially predatory and scavenging birds. No medical device can rapidly test for AR exposure of avian wildlife. Prothrombin time (PT) is a useful biomarker for AR exposure, and multiple commercially available point-of-care (POC) devices measure PT of humans, and domestic and companion mammals. We evaluated the potential of one commercially available POC device, the Coag-Sense® PT/INR Monitoring System, to rapidly detect AR exposure of living birds of prey. The Coag-Sense device delivered repeatable PT measurements on avian blood samples collected from four species of raptors trapped during migration (Intraclass Correlation Coefficient > 0.9; overall intra-sample variation CV: 5.7%). However, PT measurements reported by the Coag-Sense system from 81 ferruginous hawk (Buteo regalis) nestlings were not correlated to those measured by a one-stage laboratory avian PT assay (r = − 0.017, p = 0.88). Although precise, the lack of agreement in PT estimates from the Coag-Sense device and the laboratory assay indicates that this device is not suitable for detecting potential AR exposure of birds of prey. The lack of suitability may be related to the use of a mammalian reagent in the clotting reaction, suggesting that the device may perform better in testing mammalian wildlife

Timing of activity can reveal an organism's efforts to optimize foraging either by minimizing energy loss through passive movement or by maximizing energetic gain through foraging. Here, we assess whether signals of either of these strategies are detectable in the timing of activity of daily, local movements by birds. We compare the similarities of timing of movement activity among species using six temporal variables: start of activity relative to sunrise, end of activity relative to sunset, relative speed at midday, number of movement bouts, bout duration and proportion of active daytime hours. We test for the influence of flight mode and foraging habitat on the timing of movement activity across avian guilds. We used 64 570 days of GPS movement data collected between 2002 and 2019 for local (non‐migratory) movements of 991 birds from 49 species, representing 14 orders. Dissimilarity among daily activity patterns was best explained by flight mode. Terrestrial soaring birds began activity later and stopped activity earlier than pelagic soaring or flapping birds. Broad‐scale foraging habitat explained less of the clustering patterns because of divergent timing of active periods of pelagic surface and diving foragers. Among pelagic birds, surface foragers were active throughout all 24 hrs of the day while diving foragers matched their active hours more closely to daylight hours. Pelagic surface foragers also had the greatest daily foraging distances, which was consistent with their daytime activity patterns. This study demonstrates that flight mode and foraging habitat influence temporal patterns of daily movement activity of birds.

Scientific study of raptors often requires the use of a lure to capture individuals for marking or collecting various data and samples. Live lure owls in the genus Bubo are commonly used with mist nets or dho-gazas to trap nesting raptors, but the use of these live lures presents ethical, logistical, and financial challenges. Although owls mounted by taxidermists and mechanical owls have been used in place of a live bird, the success of these types of lures varies widely. We created a more realistic mechanical owl with a greater range of motion than previous models, and then tested the owl on six raptor species in a variety of habitats. For all but one species, capture rates using our mechanical owl were similar to or slightly higher than those reported in studies using live lure owls or previously designed mechanical owls. Time to rapture of Northern Goshawks (Accipiter gentilis) was, on average, 8 min faster when using our mechanical owl compared to a live owl. Cost analysis revealed that both the initial expense and long-term maintenance of a mechanical owl were less than that of a live lure owl. Mechanical owls can be a useful tool for capturing raptors. Although there are some drawbacks to using a mechanical owl, our results suggest that mechanical birds are comparable to live lure owls and we believe the benefits of using a mechanical owl often outweigh the costs.

Western Burrowing Owls (Athene cunicularia hypugaea) frequently nest near agricultural lands. In southwestern Idaho, greater population density in agricultural landscapes appears to be driven in part by reliable and abundant prey populations. However, these potential benefits may be offset if agricultural land use increases pesticide exposure, especially during the sensitive reproduction period. Thus, we investigated the extent to which Burrowing Owls nesting near croplands within the Morley Nelson Snake River Birds of Prey National Conservation Area (NCA), Idaho, were exposed to organophosphate (OP), carbamate (CB), and/or organochlorine (OC) pesticides. We examined plasma cholinesterase activity, OP and CB residues in foot-wash samples, and OCs in soils and whole egg contents collected from owls and their nests along a distance gradient from agricultural fields. We further measured eggshell thickness to assess potential for thinning from OC exposure. There was no inhibition of cholinesterase activities in adult or nestling owls near agriculture, and foot-wash samples from adults tested negative for OP and CB pesticides. The OC p,p'-DDE, a metabolite of DDT, occurred in eggs at 27 of 58 nests, but there was some evidence that concentrations increased with increasing distance from agriculture. Concentrations of p,p'-DDE in eggs were relatively low compared to harmful levels in other avian species, were not correlated with eggshell thickness, and did not appear to reduce nesting success. Neither DDT, its metabolites, nor any other OCs were detected in soil samples from local owl breeding areas. These results indicate that p,p'-DDE, organophosphate, and carbamate exposure were not causing toxicity or reproductive impairment of Burrowing Owls in the NCA during our study years.

The Short-eared Owl (Asio flammeus) is an open-country species breeding in the northern United States and Canada, and has likely experienced a long-term, range-wide, and substantial decline. However, the cause and magnitude of the decline is not well understood. We set forth to address the first two of six previously proposed conservation priorities to be addressed for this species: (1) better define habitat use and (2) improve population monitoring. We recruited 131 volunteers to survey over 6.2 million ha within the state of Idaho for Short-eared Owls during the 2015 breeding season. We surveyed 75 transects, 71 of which were surveyed twice, and detected Short-eared Owls on 27 transects. We performed multiscale occupancy modeling to identify habitat associations, and performed multiscale abundance modeling to generate a state-wide population estimate. Our results suggest that within the state of Idaho, Short-eared Owls are more often found in areas with marshland or riparian habitat or areas with greater amounts of sagebrush habitat at the 1750 ha transect scale. At the 50 ha point scale, Short-eared Owls tend to associate positively with fallow and bare dirt agricultural land and negatively with grassland. Cropland was not chosen at the broader transect scale suggesting that Short-eared Owls may prefer more heterogeneous landscapes. On the surface our results may seem contradictory to the presumed land use by a "grassland" species; however, the grasslands of the Intermountain West, consisting largely of invasive cheatgrass (Bromus tectorum), lack the complex structure shown to be preferred by these owls. We suggest the local adaptation to agriculture represents the next best habitat to their historical native habitat preferences. Regardless, we have confirmed regional differences that should be considered in conservation planning for this species. Last, our results demonstrate the feasibility, efficiency, and effectiveness of utilizing public participation in scientific research to achieve a robust sampling methodology across the broad geography of the Intermountain West.