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Endangered species recovery programs seek to restore populations to self-sustaining levels. Nonetheless, many recovering species require continuing management to compensate for persistent threats in their environment. Judging true recovery in the face of this management is often difficult, impeding thorough analysis of the success of conservation programs. We illustrate these challenges with a multidisciplinary study of one of the world’s rarest birds—the California condor (Gymnogyps californianus). California condors were brought to the brink of extinction, in part, because of lead poisoning, and lead poisoning remains a significant threat today. We evaluated individual lead-related health effects, the efficacy of current efforts to prevent lead-caused deaths, and the consequences of any reduction in currently intensive management actions. Our results show that condors in California remain chronically exposed to harmful levels of lead; 30% of the annual blood samples collected from condors indicate lead exposure (blood lead ≥ 200 ng/mL) that causes significant subclinical health effects, measured as >60% inhibition of the heme biosynthetic enzyme δ-aminolevulinic acid dehydratase. Furthermore, each year, ∼20% of free-flying birds have blood lead levels (≥450 ng/mL) that indicate the need for clinical intervention to avert morbidity and mortality. Lead isotopic analysis shows that lead-based ammunition is the principle source of lead poisoning in condors. Finally, population models based on condor demographic data show that the condor’s apparent recovery is solely because of intensive ongoing management, with the only hope of achieving true recovery dependent on the elimination or substantial reduction of lead poisoning rates.

Reintroduction of endangered species is wrought with many challenges, but one often overlooked challenge is the threat of predation of naïve individuals. Individuals lacking the insight to avoid predators can become easy prey and even showcase predators capitalizing on the lack of anti‐predator behavior. In California, California condors (Gymnogyps californianus) have slowly been recovering since the implementation of recovery actions and management. However, here we report an instance of where three California condors were preyed upon by a puma (Puma concolor) from 28 November to 30 December 2010 near Bitter Creek National Wildlife Refuge, Kern County, California, USA. The puma cached all three condor carcasses and was detected on a nearby camera trap revisiting the carcasses; scat was also identified nearby. This rare photographic documentation not only highlights the relatively unexplored ecological relationship between pumas and California condors but also showcases the need to understand the role predatory naïve behavior has on endangered species survivorship.

Sophisticated animal‐borne sensor systems are increasingly providing novel insight into how animals behave and move. Despite their widespread use in ecology, the diversity and expanding quality and quantity of data they produce have created a need for robust analytical methods for biological interpretation. Machine learning tools are often used to meet this need. However, their relative effectiveness is not well known and, in the case of unsupervised tools, given that they do not use validation data, their accuracy can be difficult to assess. We evaluated the effectiveness of supervised (n = 6), semi‐supervised (n = 1), and unsupervised (n = 2) approaches to analyzing accelerometry data collected from critically endangered California condors (Gymnogyps californianus). Unsupervised K‐means and EM (expectation–maximization) clustering approaches performed poorly, with adequate classification accuracies of <0.8 but very low values for kappa statistics (range: −0.02 to 0.06). The semi‐supervised nearest mean classifier was moderately effective at classification, with an overall classification accuracy of 0.61 but effective classification only of two of the four behavioral classes. Supervised random forest (RF) and k‐nearest neighbor (kNN) machine learning models were most effective at classification across all behavior types, with overall accuracies >0.81. Kappa statistics were also highest for RF and kNN, in most cases substantially greater than for other modeling approaches. Unsupervised modeling, which is commonly used for the classification of a priori‐defined behaviors in telemetry data, can provide useful information but likely is instead better suited to post hoc definition of generalized behavioral states. This work also shows the potential for substantial variation in classification accuracy among different machine learning approaches and among different metrics of accuracy. As such, when analyzing biotelemetry data, best practices appear to call for the evaluation of several machine learning techniques and several measures of accuracy for each dataset under consideration. Despite the widespread use of advanced bio‐logging tools, the quantity of data they produce has created a need for robust analytical methods for biological interpretation. Here we evaluate the effectiveness of 6 supervised, 1 semi‐supervised, and 2 unsupervised machine learning tools for the analysis of acceleration data from critically endangered California condors. Unsupervised classification, which is commonly used for the classification of a priori‐defined behaviors in telemetry data, likely is instead better suited to the post hoc definition of generalized behavioral states.

Conservation practitioners are increasingly looking to species translocations as a tool to recover imperiled taxa. Quantitative predictions of where animals are likely to move when released into new areas would allow managers to better address the social, institutional, and ecological dimensions of conservation translocations. Using >5 million California condor (Gymnogyps californianus) occurrence locations from 75 individuals, we developed and tested circuit-based models to predict condor movement away from release sites. We found that circuit-based models of electrical current were well calibrated to the distribution of condor movement data in southern and central California (continuous Boyce Index = 0.86 and 0.98, respectively). Model calibration was improved in southern California when additional nodes were added to the circuit to account for nesting and feeding areas, where condor movement densities were higher (continuous Boyce Index = 0.95). Circuit-based projections of electrical current around a proposed release site in northern California comported with the condor's historical distribution and revealed that, initially, condor movements would likely be most concentrated in northwestern California and southwest Oregon. Landscape linkage maps, which incorporate information on landscape resistance, complement circuit-based models and aid in the identification of specific avenues for population connectivity or areas where movement between populations may be constrained. We found landscape linkages in the Coast Range and the Sierra Nevada provided the most connectivity to a proposed reintroduction site in northern California. Our methods are applicable to conservation translocations for other species and are flexible, allowing researchers to develop multiple competing hypotheses when there are uncertainties about landscape or social attractants, or uncertainties in the landscape conductance surface.

Small bowel obstruction (SBO) secondary to intussusception of Meckel’s diverticulum (MD) is a rare cause of acute abdominal pain that may warrant urgent surgical treatment. Volvulus or intussusception of the small bowel with presence of MD as the lead point is the most commonly reported etiology of Meckel’s related obstructions. We report an interesting case of a small bowel obstruction caused by the intussusception of an MD within its own lumen. The case involves a 30-year-old male who presented to the emergency room with acute, severe abdominal pain with an abdominal computed tomography (CT) showing a distal high-grade SBO. Decision was made to take the patient to the operating room urgently due to his clinical examination and radiologic imaging, specifically CT scan. Diagnostic laparoscopy was performed and subsequently converted to an exploratory laparotomy, which revealed the intussuscepted MD with focal necrosis into the distal small bowel causing an SBO. A segmental small bowel resection with hand sewn primary anastomosis was performed. The case presents an interesting challenge in deciding when to take a patient with an SBO to the operating room versus initial conservative management and what the treatment should be if an MD is encountered. In addition, the case emphasizes the importance of history and physical exam findings in coordination with radiologic imaging in helping to make appropriate decisions in a timely manner for operative vs conservative management of an SBO. It reminds us that, Meckel’s diverticulum, although less commonly the cause of a small bowel obstruction in the adult population, needs to be on the differential diagnosis and we need to have a high clinical suspicion for this possibility to ensure appropriate treatment in a timely manner.

Wind-induced pointing errors are a serious concern for large-aperture high-frequency radio telescopes. In this paper, we describe the implementation of an optical quadrant detector instrument that can detect and provide a correction signal for wind-induced pointing errors on the 100 m diameter Green Bank Telescope (GBT). The instrument was calibrated using a combination of astronomical measurements and metrology. We find that the main wind-induced pointing errors on timescales of minutes are caused by the feed arm being blown along the direction of the wind vector. We also find that wind-induced structural excitation is virtually nonexistent. We have implemented offline software to apply pointing corrections to the data from imaging instruments such as the MUSTANG 3.3 mm bolometer array, which can recover∼70% ∼ 70 % of sensitivity lost due to wind-induced pointing errors. We have also performed preliminary tests that show great promise for correcting these pointing errors in real time using the telescope’s subreflector servo system in combination with the quadrant detector signal.

Large avian scavengers are among the most vulnerable vertebrates, and many of their populations have declined severely in recent decades. To help mitigate this marked reduction in abundance, supplementary feeding stations (SFS; colloquially termed \"vulture restaurants\") have been created worldwide, often without consideration of the scientific evidence supporting the suitability of the practice. SFS have been effective and important tools for conservation and reintroduction of avian scavengers. However, negative consequences can result from large aggregations of individual birds, disrupting intraguild processes and promoting densitydependent decreases in productivity. At the community level, SFS favor the congregation of predators (ie facultative scavengers), increasing prédation risk on small-and medium-sized vertebrates in the vicinity of the SFS. These feeding stations might also affect processes of natural selection and even render populations maladapted to their natural environments. We also examine future scenarios for avian scavengers in relation to ecosystem services, to changes in agro-grazing economies and in land uses, and ultimately to rewilding landscapes where SFS play a controversial role.

Lead poisoning is an important conservation concern for wildlife, and scavenging birds are especially at risk from consumption of carcasses of animals killed with lead ammunition. Because current methods to identify lead exposure require animal capture and blood collection, management would benefit from the development of a less costly and noninvasive behavioral test for illness in wild animals. We attempted to design such a test to identify lead exposure in California condors (Gymnogyps californianus) that we tracked with global positioning system (GPS) telemetry in southern California, USA, 2013–2016. We measured blood-lead concentrations in tracked birds and expected that flight behavior would be influenced by lead exposure; thus, we measured the effect of blood-lead concentrations on 2 different types of movement rates and on the proportion of time condors spent in flight. We found no effect of lead exposure on any of these 3 behavioral metrics. Our work suggests that the measurements we took of flight behaviors were not a useful tool in predicting lead exposure in the mildly to moderately exposed birds we studied. Wild birds are effective at hiding illness, especially condors who have a strong social hierarchy in which showing weakness is a disadvantage. However, focusing on behaviors other than flight, expanding the sample studied to include birds with a wider range of lead concentration values, or analyzing tissues such as feathers (rather than, or in addition to, blood) may be more useful for identification of lead exposure and other diseases that may limit wildlife populations.

Large‐scale poisoning events are common to scavenging bird species that forage communally, many of which are in decline. To reduce the threat of poisoning and compensate for other persistent threats, management, including supplemental feeding, is ongoing for many reintroduced and endangered vulture populations. Through a longitudinal study of lead exposure in California condors (Gymnogyps californianus), we illustrate the conservation challenges inherent in reintroduction of an endangered species to the wild when pervasive threats have not been eliminated. We evaluated population‐wide patterns in blood lead levels from 1997 to 2011 and assessed a broad range of putative demographic, behavioral, and environmental risk factors for elevated lead exposure among reintroduced California condors in California (United States). We also assessed the effectiveness of lead ammunition regulations within the condor's range in California by comparing condor blood lead levels before and after implementation of the regulations. Lead exposure was a pervasive threat to California condors despite recent regulations limiting lead ammunition use. In addition, condor lead levels significantly increased as age and independence from intensive management increased, including increasing time spent away from managed release sites, and decreasing reliance on food provisions. Greater independence among an increasing number of reintroduced condors has therefore elevated the population's risk of lead exposure and limited the effectiveness of lead reduction efforts to date. Our findings highlight the challenges of restoring endangered vulture populations as they mature and become less reliant on management actions necessary to compensate for persistent threats.

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.