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Lead (Pb) is a heavy metal with no clear biological benefit that is toxic to wildlife and humans. Although Pb has been banned from several consumer products, it is not regulated in ammunition for big‐game hunting (e.g., cervids) in New York, USA. Wildlife species that scavenge remains of game harvested with Pb ammunition can be exposed to bullet fragments through ingestion and potentially develop toxicosis. To make evidence‐based decisions for reducing risk from bullet‐derived Pb, we first empirically identified avian and mammalian scavengers of white‐tailed deer (Odocoileus virginianus) remains in New York through an online survey during July‐August 2023, where community members submitted images of scavengers from game cameras. We conducted species vulnerability and utility assessments using published evidence and pre‐existing frameworks. Despite inherent limitations, we documented an extensive array of avian (n = 17) and mammalian (n = 14) scavengers. We estimated bald eagles (Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) as most vulnerable to Pb toxicosis, followed collectively by American goshawks (Accipiter atricapillus), American crows (Corvus brachyrhynchos), and common ravens (C. corax). We also determined bald eagles to be best‐suited as bioindicators of bullet‐derived Pb, followed by American goshawks. Red‐tailed hawks (Buteo jamaicensis) and great horned owls (Bubo virginianus) equally ranked third. Integrating vulnerability and utility assessments point to bald eagles as the most vulnerable scavengers to Pb toxicosis and best‐suited bioindicators of bullet‐derived Pb. Because regulation of Pb ammunition for big‐game hunting is an ongoing socio‐political issue, wildlife managers and conservationists can address health risks through monitoring species vulnerable to toxicosis and instituting surveillance programs using the most effective bioindicators. [ABSTRACT FROM AUTHOR]

Over the last 10 years, the spawning population of invasive pink salmon (Oncorhynchus gorbuscha) has increased in the river systems in northern Norway to a level that is causing concern about their impact on endemic fauna and ecosystem processes. The scale of transfer of pink salmon carcasses into the terrestrial ecosystem is likely to be a key determinant of terrestrial impact. Bears (Ursus sp.) are responsible for most such transfers in North America but are rare in Norway. The white‐tailed eagle (Haliaeetus albicilla) is common however, and a candidate to be a main cause of such transfers. To evaluate this hypothesis, data on the abundance of white‐tailed eagles and pink salmon were collected along the river Skallelv in northern Norway in 2021, a year the pink salmon spawned in the river, and in 2022, a year no pink salmon spawned in the river. The abundance of white‐tailed eagles along the river was much higher the year pink salmon spawned in the river. Furthermore, white‐tailed eagles were observed aggregating and catching pink salmon where and when pink salmon were present at the spawning and post‐spawning stages. Based on our observations, we suggest that the white‐tailed eagle is the main species involved in the transport of pink salmon from the river into the riparian zone in northern Norway and that other scavengers, in particular the red fox (Vulpes vulpes) and common raven (Corvus corax), play an important role in transporting pink salmon carcasses from the riparian zone to the wider terrestrial ecosystem. [ABSTRACT FROM AUTHOR]

Monitoring of breeding success in wildlife is key for evaluating population trends and support conservation measures. However, it is challenging depending on breeding places or non-accessible habitat. In recent years, new technologies were applied to studies of bird biology, i.e. drones. UAV (drones) are available to study new aspects of bird ecology, which are not available using traditional methods. The Raven Corvus corax predominantly nests in upper tree canopies or on high cliffs. Hence, it is challenging to monitor it breeding success from the ground. Our study were conducted in forests in NE Poland, on the 77 arboreal Raven nests in 2021–2022. By using drones, we investigated (i) whether the classic data on breeding success from ground observations differ from those of nest inspections via drone, and (ii) to what extent the adult birds behave when the drone is used at the nest. The inspection from the ground failed to determine the contents of as many as 30% of the occupied nests. Inspections using a drone and those made from the ground yielded different results, as aerial assessment showed a higher number of the young (respectively 1.93 vs. 3.22 per successful brood). Broods with three young accounted for 6.5% of nests controlled from the ground and 23.3% using a drone, while broods with two young accounted for 33.8% and 10.4% of nests, respectively. During most of the inspected nests (65% of the cases), adult birds sat nearby in the tree tops and called. In 12% of the cases, the birds flew close to the nest, passing the drone at a distance of more than 20 m, and did not attempt to approach the device. In four cases, adult birds closed the drone at less than 10 m. A direct collision did not happen. The most vital reactions were recorded in several instances (only 4.2%) in which the birds were not near the nest when the inspection began but arrived during the inspection. Drone surveys have revealed previously un-described behavior of birds, alarmed at the examination of empty nests. In 50 nests, 65% of the cases, the Raven tolerated the drone's presence at the nest, although the birds showed concern and occasionally defensive reactions. It seems that the adverse reaction of birds is weaker when they associate the appearance of a drone with human presence. Key recommendations: control in teams of two - operator and observer, starting end landing in close vicinity of the nest tree, immediate interruption of flight if birds react, forbade flying directly over the nest. It is advisable to check the reaction of adult Ravens to drone inspections of nests with small nestlings. To sum up, our study showed that the drone inspections did not harm the adult birds but provides a more reliable data for reproduction than the observation from ground. [ABSTRACT FROM AUTHOR]

Invasive fungal aspergillosis is a leading cause of morbidity and mortality in many species including avian species such as common ravens (Corvus corax). Methods were developed for mass spectral determination of voriconazole in raven plasma as a means of determining pharmacokinetics of this antifungal agent. Without further development, GC/MS/MS (gas chromatography-tandem quadrupole mass spectrometry) proved to be inferior to LC/MS/MS (liquid chromatography-tandem quadrupole mass spectrometry) for measurement of voriconazole levels in treated raven plasma owing to numerous heat-induced breakdown products despite protection of voriconazole functional groups with trimethylsilyl moieties. LC/MS/MS measurement revealed in multi-dosing experiments that the ravens were capable of rapid or ultrarapid metabolism of voriconazole. This accounted for the animals' inability to raise the drug into the therapeutic range regardless of dosing regimen unless cytochrome P450 (CYP) inhibitors were included. Strategic selection of CYP inhibitors showed that of four selected compounds including cimetidine, enrofloxacin and omeprazole, only ciprofloxacin (Cipro) was able to maintain voriconazole levels in the therapeutic range until the end of the dosing period. The optimal method of administration involved maintenance doses of voriconazole at 6 mg/kg and ciprofloxacin at 20 mg/kg. Higher doses of voriconazole such as 18 mg/kg were also tenable without apparent induction of toxicity. Although most species employ CYP2C19 to metabolize voriconazole, it was necessary to speculate that voriconazole might be subject to metabolism by CYP1A2 in the ravens to explain the utility of ciprofloxacin, a previously unknown enzymatic route. Finally, despite its widespread catalog of CYP inhibitions including CYP1A2 and CYP2C19, cimetidine may be inadequate at enhancing voriconazole levels owing to its known effects on raising gastric pH, a result that may limit voriconazole solubility. [ABSTRACT FROM AUTHOR]

In avian ecosystems, habitat dynamics significantly influence bird activities. This study was conducted from July to November 2019 in the Badgoi coniferous forest, Upper Dir, Khyber Pakhtunkhwa, Pakistan. Distance Sampling Point Count method was utilized in the study to quantify the correlation between bird abundance and habitat structure. Meticulously observing 485 birds spanning 28 species and 20 families, dominant species included the Common Raven (14.4%), Pine Siskin (11.30%), and House Sparrow (10.72%). Conversely, the Red Crossbill, Gray-back Shrike, and Yellow Tit emerged as the rarest inhabitants (0.4%, 0.2%, each). Blue Kail dominated the botanical landscape at 14.599%, while Chinar stood as the rarest species (7.299%). Shrubbery diversity showcased Simru as the most abundant (14.038%) and Kala Simlu as the rarest (6.836%). Correlational analyses highlighted the intimate association between bird species and ecological components, including vegetation structure and microclimate variables. Density analysis unveiled species-specific variations in populations, emphasizing diverse foraging guilds and nuanced resource utilization. The study sets the groundwork for future research, emphasizing genetics, advanced monitoring technologies, and collaborative conservation efforts, contributing to the long-term well-being of bird populations in the Badgoi forest. [ABSTRACT FROM AUTHOR]

Allochthonous inputs often link nutrient cycles between different ecosystems as nitrogen (N) that originates in one ecosystem is transferred to another. Mobile animals such as birds and fish can translocate nutrients between locations. Consequently, animal-mediated nutrient subsidies can shape plant communities, especially in nutrient-poor ecosystems. Terrestrial cliffs are typically nutrient-poor, receiving N from atmospheric deposition and cliff-top runoff. Cliff nesting birds deposit N-rich excrement onto the cliff during nesting, yet this potential nutrient input has rarely been demonstrated. Here we document an allochthonous input of N from cliff-nesting birds to terrestrial cliff vegetation. We sampled mineral N and vegetation on eight cliff systems in western North Carolina (USA) with nests from peregrine falcon (F. peregrinus; two sites) and common raven (Corvus corax ; five sites). Two sites had nests but species identity was not confirmed. Cliff faces below bird nests had higher levels of ammonium (NH 4 +) than did faces without nests. Both ammonium and nitrate (NO 3 −) explained variability in cliff vegetation community composition, but site-level characteristics explained more of the variation than did N inputs alone. Lichens, the dominant taxonomic group, contributed the most to this variation and had higher species richness and diversity below nests. Indicator species analysis identified two nitrophilic lichen species below nests: Flavoplaca citrina and Physcia caesia. A third nitrophilic lichen, Polycauliona candelaria (syn. Xanthoria candelaria) was also found under nests. Bird excrement is likely a significant subsidy to nutrient-poor terrestrial cliff ecosystems, thus linking cliffs to more productive ecosystems and highlighting the need to include birds in conservation and management of cliffs. [Display omitted] [ABSTRACT FROM AUTHOR]

In temperate regions, larger mammalian carrion naturally occurs in terrestrial landscapes as a pulsed resource towards the end of the winter through enhanced ungulate mortality due to starvation or exhaustion. The return of large carnivores in Central Europe provides carrion more equally throughout the year and the active enhancement of carrion for biodiversity by game managers has increased, raising the question of how different scavengers respond to the temporal variation in carrion supply. To address this question, we experimentally deployed 106 cervid carcasses throughout the year in a temperate forest of south-eastern Germany on two types of plots: permanent (i.e., site with multiple subsequent deployments) or random (i.e., site with unique deployment), and reported vertebrate scavenger visitations by camera trapping. Deployment on random or permanent sites did not affect carrion use by any single species. Generalized additive modelling revealed that vertebrate scavenging peaked in the winter season and summer independent of carrion supply. Still, different scavenger species showed different temporal patterns. While wild boar as ungulate omnivores did not display any seasonal patterns, avian scavengers showed significant variation in visitation rates. The mesopredator red fox consumed carrion significantly more often from late winter to summer, while pine marten was present at carrion only during winter. Finally, the specialist large carnivore Eurasian lynx, visited carrion sites most frequently in late winter and early spring. Our results suggest that global warming might impact some groups of vertebrate scavengers more strongly than others by reducing carrion availability in late winter, while returning carnivores could mitigate these impacts. [ABSTRACT FROM AUTHOR]

Multiple raptors show juvenile plumage that is substantially different from that of their parents. Here, we test the prediction that the colouration of the juvenile northern goshawk Accipiter gentilis resembling the colouration of the common buzzard Buteo buteo acts as a form of aggressive mimicry. The goshawk specialises in hunting larger birds and mammals up to the size of geese or hares, while the buzzard preys mostly on small rodents. Larger birds may thus consider juvenile goshawks as less dangerous raptors, and the juvenile goshawk may thus gain an advantage when hunting. We used the Eurasian magpie Pica pica, a common prey of the goshawk, to test this prediction. We compared the behavioural responses of magpie parents defending their freshly fledged young towards mounts of an adult goshawk, juvenile goshawk, and buzzard. To be able to assess whether this behaviour differs from responses to a nest predator and a harmless bird we also presented a common raven Corvus corax and common pheasant Phasianus colchicus as baseline stimuli. Both juvenile and adult goshawks elicited antipredatory behaviour, but magpies took more risks facing juvenile goshawks. Additionally, the intensity of antipredatory behaviour towards the juvenile goshawk was also higher than towards the buzzard. We thus conclude that magpies do distinguish between juvenile and adult goshawks, as well as they do distinguish juvenile goshawks from buzzards. They are able to assess the threat particular raptors represent and respond accordingly. Analysis of spectral reflectance of stuffed specimens of these three raptors suggests there are differences, which can be used for the appropriate recognition. In conclusion, we cannot confirm the hypothesis of aggressive mimicry in juvenile goshawks that interact with magpies. [ABSTRACT FROM AUTHOR]

OBJECTIVE To determine if a cytochrome (CYP) P450 enzyme inhibitor can maintain therapeutic plasma levels of voriconazole when administered orally. ANIMALS 11 healthy, common ravens (Corvus corax). METHODS Birds were randomly assigned to pilot study groups to receive voriconazole orally alone or combined with a CYP inhibitor. Pilot studies with 3 CYP inhibitors launched the main study using ciprofloxacin (20 mg/kg) followed 1 hour later by voriconazole (6 mg/kg) every 12 hours for 14 days. Plasma voriconazole concentrations were measured at various time points by HPLC-MS. The study period lasted from September 2016 to December 2020. RESULTS The birds failed to maintain therapeutic plasma levels of voriconazole during multidose administration alone or following preadministration with various CYP inhibitors. For the 14-day study period, voriconazole reached a maximum plasma concentration of 2.99 μg/mL with a time-to-peak drug concentration of 1.2 hours following preadministration of ciprofloxacin. One bird was removed from the study due to lethargy, but the other birds completed the study without incident. CLINICAL RELEVANCE Ciprofloxacin (20 mg/kg) followed by voriconazole (6 mg/kg) maintained the concentration of voriconazole within the recommended therapeutic range of 0.5 to 5 μg/mL without toxicity. Ciprofloxacin prevented the saturable metabolism of voriconazole and maintained these levels for the study duration. This drug combination could be used in the treatment of chronic aspergillosis in the common raven. [ABSTRACT FROM AUTHOR]

The article explores the principle of reciprocity, which is the act of individuals helping others with the expectation of receiving help in return. The author discusses how reciprocity is observed in various species, including bacteria, insects, birds, and humans. The article also examines the cognitive abilities required for reciprocity and compares its presence in different animal species, including primates. The author acknowledges that there are still many unanswered questions about reciprocity and calls for further research in this area. The article emphasizes the interdisciplinary nature of studying reciprocity and highlights the importance of collaboration between different academic fields. [Extracted from the article]

The wild boar (Sus scrofa) is a social animal species native to Eurasia. During the last decade, the wild boar population in Estonia has been severely affected by the African swine fever virus (ASFV), which has also affected domestic pig farming. The potential transmission routes of ASFV remain unclear and are currently under intensive investigation. This pilot study aimed to clarify the frequency and characteristics of contacts between living wild boars and the carcasses of their conspecifics, which could play a role in the transmission of ASFV. Wild animals' contact and scavenging behavior on wild boar carcasses were studied using trail cameras in an experimental setting on Hiiumaa, Western Estonia. Four legally hunted carcasses were used in the present study. This study aimed to determine whether intraspecies scavenging occurs in wild boars. The persistence of ASFV DNA in soil contaminated with infected wild boar carcasses was investigated separately. Among the 17 identified wildlife species that visited wild boar carcasses, the common raven (Corvus corax) was the most frequent one (37.26%), followed by raccoon dogs (Nyctereutes procyonoides; 4.25%), carcass conspecific/wild boars (3.16%), and red foxes (Vulpes vulpes; 2.14%). Regarding the direct contact with the carcass, the same species ranking was detected: common raven (74.95%), raccoon dogs (9.94%), wild boars (4.21%), and red foxes (4.21%). No clear signs of cannibalism were noted among the wild boars, although brief physical contact with the carcasses was evident. The persistence of ASFV DNA in soil contaminated by infected wild boar carcasses was investigated separately. This study revealed that ASFV DNA from infected carcasses could be detected in forest soil for prolonged periods, even after removing the carcasses. Hence, the carcasses of infected wild boarsmay play an important role in spreading the African swine fever virus in wild boar populations; thus, prompt removal and disinfection of the soil could be considered necessary to limit the spread of the infection. [ABSTRACT FROM AUTHOR]

Ravens and other corvids are renowned for their 'intelligence'. For long, this reputation has been based primarily on anecdotes but in the last decades experimental evidence for impressive cognitive skills has accumulated within and across species. While we begin to understand the building blocks of corvid cognition, the question remains why these birds have evolved such skills. Focusing on Northern Ravens Corvus corax, I here try to tackle this question by relating current hypotheses on brain evolution to recent empirical data on challenges faced in the birds' daily life. Results show that foraging ravens meet several assumptions for applying social intelligence: (1) they meet repeatedly at foraging sites, albeit individuals have different site preferences and vary in grouping dynamics; (1) foraging groups are structured by dominance rank hierarchies and social bonds; (3) individual ravens memorize former group members and their relationship valence over years, deduce third-party relationships and use their social knowledge in daily life by supporting others in conflicts and intervening in others' affiliations. Hence, ravens' socio-cognitive skills may be strongly shaped by the 'complex' social environment experienced as non-breeders. [ABSTRACT FROM AUTHOR]

Preening behaviours are widespread in extant birds. While most birds appear to autopreen (self-directed preening), allopreening (preening directed at conspecifics) seems to have emerged only in certain species, but across many families. Allopreening has been hypothesised to reinforce mutual relationships and cooperation between individuals, and to underpin various socio-cognitive abilities. Palaeognathae is a bird group exhibiting neurocognitively plesiomorphic traits compared to other birds. They share many features with non-avian paravian dinosaurs and are thus important for the study of cognitive evolution in birds. Despite this, and the important correlation of allopreening with many complicated social behaviours, allopreening has not been systematically studied in Palaeognathae. Therefore, we examined the preening behaviours in four species of palaeognaths: common ostriches (Struthio camelus), greater rheas (Rhea americana), emus (Dromaius novaehollandiae), and elegant crested tinamous (Eudromia elegans). We compared findings with common ravens (Corvus corax), a neognath species known for its allopreening and complex social cognition. We found autopreening, but no allopreening, in the palaeognath species, while both autopreening and allopreening was found in common ravens. The absence of allopreening in Palaeognathae suggests an emergence of this behaviour within Neognathae. We contextualise our results in relation to the socio-cognitive underpinnings of allopreening and its implications for the understanding of the evolution of socio-cognitive abilities in non-avian paravian dinosaurs and early birds. [ABSTRACT FROM AUTHOR]

Algeria is situated in the transition zone between two biogeographical regions, the Western Palaearctic and the Afrotropical. It covers a vast territory characterized by three main ecosystems: the Tell, the plateaux, and the Sahara. The two species of crows, the Brown-necked Raven Corvus ruficollis and the Northern Raven Corvus corax occupy very distinct territories, the first frequenting the southern part of the Saharan Atlas and the second the northern part. The incursion of the Pied Crow Corvus albus into the territory occupied by the Northern Raven was reported for the first time when two individuals of this species were observed in a technical landfill center located between Aflou and Gueltat Sidi Saad (34°13'12" N, 2°01'33" E, 1235 m.a.s.l.) on April 06, 2023. This also shows the cohabitation of this species with the other two Crow species. [ABSTRACT FROM AUTHOR]

Anthropogenic resource subsidization across western ecosystems has contributed to widespread increases in generalist avian predators, including common ravens (Corvus corax; hereafter, raven). Ravens are adept nest predators and can negatively impact species of conservation concern. Predation effects from ravens are especially concerning for greater sage‐grouse (Centrocercus urophasianus; hereafter, sage‐grouse), which have experienced prolonged population decline. Our objectives were to quantify spatiotemporal patterns in raven density, evaluate sage‐grouse nest success concurrent with fluctuating raven densities, and demonstrate a spatially explicit decision support tool to guide management applications to appropriate conflict areas. We combined ~28,000 raven point count surveys with data from more than 900 sage‐grouse nests between 2009 and 2019 within the Great Basin, USA. We modeled variation in raven density using a Bayesian hierarchical distance sampling approach with environmental covariates on detection and abundance. Concurrently, we modeled sage‐grouse nest survival using a hierarchical frailty model as a function of raven density and other environmental covariates that influence the risk of nest failure. Raven density commonly exceeded 0.5 ravens km−2 and increased at low elevations with more anthropogenic development and/or agriculture. Reduced sage‐grouse nest survival was strongly associated with elevated raven density (e.g., >0.5 ravens km−2) and varied with topographic ruggedness, shrub cover, and burned areas. For conservation application, we developed a spatially explicit planning tool that predicts nest survival under current and reduced raven numbers within the Great Basin to help direct management actions to localized areas where sage‐grouse nests are at highest risk of failure. Our modeling framework can be generalized to multiple species where spatially registered abundance and demographic data are available. [ABSTRACT FROM AUTHOR]

Gaze following refers to the ability to co-orient with others' gaze directions. Ontogenetic studies on gaze following in animals have predominantly used human experimenters as demonstrators. It is, however, likely that developing animals are initially more attuned to individuals from their own species, which might result in differences in the ontogenetic onset of gaze following with human and conspecific demonstrators. "Checking back" is a signature behaviour in the gaze following repertoires of humans, apes, and some Old world monkeys. It is commonly interpreted as a representation of the referentiality of gaze and is thus diagnostic of social predictions. Recently, "checking back" has been discovered in four avian species, suggesting a shared skill among birds. To investigate effects of con- and allospecific demonstrators on gaze following responses, we studied visual co-orientations of four hand-raised juvenile common ravens (Corvus corax) with human and conspecific gaze cues. Moreover, we for the first time investigated "checking back" in ravens and compared the effects of con- and allospecific demonstrators on this behaviour. Ravens followed human and conspecific gaze with no apparent differences in ontogenetic onset, but after significantly longer latencies with human demonstrators. Subjects moreover already checked back at 30 days old and did so significantly more often with conspecific demonstrators. Our findings suggest differences in processing speed and social predictions of human and conspecific gazes, indicating an underlying neurocognitive mechanism attuned to social information gathering from conspecifics. We propose more studies using conspecific demonstrators to reveal the full gaze following potential of a species. [ABSTRACT FROM AUTHOR]

The early Gravettian site of Maisières‐Canal (Belgium) was discovered in 1966, during the widening of the Canal du Centre. Emergency excavation allowed the discovery of an open‐air human occupation which yielded abundant archaeological material. A re‐examination of the well‐preserved faunal collections has expanded the bird assemblage from the 29 bones initially recognized to 78, which have been studied from an archaeozoological point of view. Six taxa were identified, including species regularly encountered in Upper Paleolithic sites, such as the snowy owl (Bubo scandiacus), the northern raven (Corvus corax), and the willow or rock ptarmigan (Lagopus sp.). Ducks (Anatinae) are by far the best represented taxa. Surprisingly, only radius fragments were recovered for ducks, most bearing breaks and tool marks. We paid special attention to this peculiar set of duck radiuses. We performed experiments on fresh duck wings to evaluate the impact of different actions on the radius. Based on our experiments, two main hypotheses emerged. This accumulation of duck radiuses may represent (1) the waste from the production of dry wings and/or (2) a supply of raw material for craft activities. However, neither of these two hypotheses can be conclusively confirmed. As well as exhibiting some discrepancies, the bird bone assemblage from Maisières‐Canal shares several characteristics with early Gravettian sites from central Europe. [ABSTRACT FROM AUTHOR]

Example of an annotated arctic chorus with calls and songs of four different tundra species: (a) the lapland longspur (Calcarius lapponicus - LALO in the dataset), (b) the ruddy turnstone (Arenaria interpres - RUTU), (c) the pectoral sandpiper (Calidris melanotos - PESA), and (d) the dunlin (Calidris alpina - DUNL). Automatic monitoring is increasingly tailored to meet the unprecedented challenges of tracking broad scale biodiversity changes, generating a multitude of data only tackled by artificial intelligence. (G) A female red phalarope (Phalaropus fulicarius - REPH) calling during a foraging bout in an arctic pond. [Extracted from the article]

Anthropogenic food subsidies can alter ecosystem processes, such as competition, predation, or nutrient transfer, and may strongly affect protected areas. Increasing recreation and ecotourism often create food subsidies, especially in the surrounding lands through fast-growing gateway communities. How the effects of these subsidies extend into protected areas when animals move across boundaries remains largely unexplored. We addressed this question by studying the movement and foraging of common ravens (Corvus corax), opportunistic scavengers that are well known to feed on predator kills and on anthropogenic food subsidies. We analyzed spatiotemporal data from 57 global positioning system (GPS)-tagged ravens, trapped within or close to Yellowstone National Park, to study their seasonal use of natural and anthropogenic food sources. Although Yellowstone National Park contains a full suite of native predators and ravens can be observed at virtually every kill site, we show that anthropogenic subsidies were utilized to a much greater extent than other natural resources, especially during winter. Important subsidies included gut piles of harvested game animals left by hunters, fat present on wastewater settling ponds, roadkill, and waste from agricultural and urban activities. These subsidies were distributed over vast areas beyond Yellowstone National Park. During fall/winter, ravens traveled longer distances (21.9 vs. 13 km) and spent more time outside Yellowstone National Park (73% of GPS points outside), mostly feeding on anthropogenic subsidies, than in spring/summer (42% of GPS points outside). This difference between seasons was more pronounced for individuals holding territories within the protected area than for those without territories. The large area over which ravens used anthropogenic food subsidies (within more than 100 km of Yellowstone National Park) affects the park's raven population and the scavenging services they provide. We suggest that the scale of resource use must be considered by managers seeking to control expanding raven populations elsewhere. [ABSTRACT FROM AUTHOR]

Shrublands globally have undergone structural changes due to plant invasions, including the expansion of native trees. Removal of native conifer trees, especially juniper (Juniperus spp.), is occurring across the Great Basin of the western U.S. to support declining sagebrush (Artemisia spp.) habitats and associated wildlife species, such as greater sage-grouse (Centrocercus urophasianus). One justification for conifer removal is that it may improve survival of sagebrush-associated wildlife by reducing the abundance of avian predators. However, the relationship between conifer expansion and predator distributions has not been explicitly evaluated. Further, although structural characteristics of habitat are important for generalist predators, overall prey abundance may also affect habitat use by predators. We examined habitat use of common ravens (Corvus corax) and red-tailed hawks (Buteo jamaicensis), two generalist predators whose populations are increasing in western North America, to variation in structural characteristics and prey distributions in sagebrush habitat that has experienced conifer expansion. Structural characteristics of habitat were important predictors of habitat use for both ravens and red-tailed hawks, whereas measures of prey abundance were unimportant for both species likely because generalist predators can use a wide variety of food resources. Ravens, but not red-tailed hawks, responded positively to increasing cover of juniper and the probability of habitat use was highest (> 0.95) where juniper cover within 100 m was > 20%. Habitat use by red-tailed hawks, but not ravens, was greater near cliffs but was not associated with juniper cover. Our study suggests that the removal of conifer in similar environments may lower the probability of habitat use for ravens, a common predator with significant impacts on many prey species. Therefore, we suggest conifer removal may improve sage-grouse reproductive success and survival depending on responses to conifer removal from other predators. Our results may be reflective of similar changes in rangeland ecosystems around the world undergoing expansion of conifer and other woody vegetation. Though species identities differ from sagebrush habitats, generalist avian predators in other habitats may have similar relationships with structural resources. [ABSTRACT FROM AUTHOR]

Nest depredation is one of the greatest threats posed to ground-nesting ducks. We employed cameras to monitor 164 duck nests (71 cinnamon teal, Spatula cyanoptera , 44 gadwall, Mareca strepera , 38 mallard, Anas platyrhynchos , and 11 nests of unknown species) in the wetlands surrounding Great Salt Lake, from 2015–2021. Of the 164 nests, 21% were successful, 73% were depredated and 7% were abandoned. We observed predators at 99 of the 119 depredated nests; predators at 20 nests went undetected. Raccoons (Procyon lotor , N = 44 depredated nests) and striped skunks (Mephitis mephitis , N = 43) were the most common of the 99 nest predators recorded. Other predators that depredated nests included long-tailed weasels (Mustela frenata), northern harriers (Circus hudsonius), California gulls (Larus californicus), Sandhill cranes (Antigone canadensis), common ravens (Corvus corax), coyotes (Canis latrans) and red foxes (Vulpes vulpes). Neither the number of eggs removed per depredation event nor the number of eggs remaining varied by predator species. Depredated nests were easier for predators to find than undisturbed, incubated nests, resulting in 68% of depredated nests being visited by multiple predators. All hens detected the approach of a predator and flushed before the predator reached the nest; no hens attempted to defend their nest or attack the predator. Only 21% of hens returned to their depredated nest, and those that did remained off their nest an average of 33 h and 23 h after their nest was depredated by a raccoon or skunk, respectively. Seventeen percent of hens resumed incubation of their depredated nest, but only 1 nest to which a hen returned successfully hatched an egg. Depredation events of raccoons and skunks were not distributed randomly during the 24-hour day, but rather occurred most often during the night and nautical twilight, and rarely during the day. Depredation events of avian predators occurred during the day, rarely during twilight, and none during the night. Depredation events during the night were more likely when the wind was calm but temperature, humidity, and actual moon illumination had no impact. Depredation events by skunks and raccoons occurred more often during the 1st and 4th phases of the moon (new moon) than in the 2nd or 3rd phase. [ABSTRACT FROM AUTHOR]

Baseline haematological and biochemical blood parameters in healthy wild birds are key to managing wild populations and to saving critically ill individuals. This knowledge is crucial for the care, rehabilitation and the release of birds after treatment in wildlife rescue centres. Plasma levels provide valuable information for the evaluation of the physical condition of animals. The objective of this study was to obtain reference values of some basic biochemical blood parameters of wild common ravens (Corvus corax). Between 2020 and 2023, we took blood samples from the wild population of common ravens in Bulgaria (n = 36). We determined the values of 18 parameters - alanine transaminase (ALT, U/I), albumin (g/l), alkaline phosphatase (ALP, U/I), amylase (U/I), aspartate transaminase (AST, U/I), calcium (mmol/l), chloride (mmol/l), cholesterol (mmol/l), creatine kinase (CK, U/I), creatinine (μmol/l), blood glucose (mmol/l), lactate dehydrogenase (LDH, U/I), magnesium (mmol/l), phosphorus (mmol/l), total bilirubin (μmol/l), total protein (g/l), triglycerides (TG, mmol/l) and uric acid (μmol/l). We made a comparative analysis including the regions in which the groups were sampled and the time of year. Most of the presented results were comparable to published values of other species from the Corvidae family and some were higher (ALP, amylase, AST, CK, total protein and uric acid levels). Most of these could be explained by the capture- and handling stress. This is the first report in official literary sources presenting some basic biochemical blood parameters of healthy wild common ravens in Bulgaria. The results may be of use to scientists, veterinarians and other researchers in rescue and rehabilitation centres and they can provide the basis for further studies with regards to animal welfare and health assessment of the species. [ABSTRACT FROM AUTHOR]

Artificial feeding is a widely used management tool, but it often attracts nontarget species, including birds, to permanent feeding sites. This study used camera traps to monitor the presence of birds at selected sites used for bear management in Dinaric forest. A large number of bird species (35) were recorded, representing roughly half of all species breeding in the surrounding area. These species were grouped based on monthly and hourly presence, and corresponded to food groups, with most belonging to granivores or scavengers. Some species, such as Pigeons (Columba sp.), Raven (Corvus corax) and Buzzard (Buteo buteo), adapted their presence to the availability of food at the feeding sites, while others were not affected by this. Both Chaffinches (Fringilla coelebs) and Jays (Garrulus glandarius) frequented the feeding sites, but their temporal presence was influenced by their biology rather than by food availability. The Sparrowhawk (Accipiter nisus) also adapted its presence to food availability, and its presence was closely associated with that of the Jay. This study confirms the temporal differences in the use of feeding sites by birds and mammals, which is likely due to their different biology and past management. This can be used to make wildlife management more efficient and reduce the undesirable effects of artificial feeding. [ABSTRACT FROM AUTHOR]

Corvids are known for their cognitive flexibility, and many have innovated various forms of tool use. Here, we review tool use and tooling in common ravens (Corvus corax) and describe additional observations. In total, they have used tools in 10 submodes and 11 modes. Of these modes, four were observed in captivity only, four in the wild only and three in both contexts. Five of these modes constitute tooling. When they manufactured tools, it was through detachment or subtraction. The purpose of most tool use was apparent, except when they used containers to transport small amounts of food that could be held in their bill and antelingual pouch (estimated to hold at least 16.2 ml). The small number of tool‐using individuals per mode and the lack of detailed descriptions limit further interpretation and generalizability. Nonetheless, ravens are likely customary tool users in three modes and show the capacity for diverse tool use, which should be examined in dedicated future experiments. [ABSTRACT FROM AUTHOR]

Operating wind-power projects often includes protecting volant wildlife. One method for doing this uses an automated system to detect, identify (through use of artificial intelligence; AI), track animals (targets) and curtail turbines when risk of a collision is high. However, assessments of the effectiveness, in terms of identification accuracy and subsequent turbine curtailment of such systems are lacking. Over 1 year, we assessed such an automated system installed at a wind project in California, USA to determine its identification accuracy and rates at which "virtual" curtailments were ordered (without slowing turbines), for eagles (intended targets) and non-eagle targets. The system correctly identified 77% of eagles and 85% of non-eagles. Curtailment orders occurred 6 times more frequently for non-eagle targets (5,439) than for eagle targets (850). Greater abundance of common ravens that were misidentified as eagles influenced the effectiveness of the system by greatly increasing unintended curtailment orders. The balance between costs (price of the IdentiFlight system, reduced energy generation, turbine wear and maintenance) and benefits (reduced collisions between intended target species and turbines) may depend upon the biological setting, speed at which operators can curtail turbines, and the objectives of the operator when considering the IdentiFlight system. [ABSTRACT FROM AUTHOR]

Mirror self-recognition (MSR) assessed by the Mark Test has been the staple test for the study of animal self-awareness. When tested in this paradigm, corvid species return discrepant results, with only the Eurasian magpies and the Indian house crow successfully passing the test so far, whereas multiple other corvid species fail. The lack of replicability of these positive results and the large divergence in applied methodologies calls into question whether the observed differences are in fact phylogenetic or methodological, and, if so, which factors facilitate the expression of MSR in some corvids. In this study, we (1) present new results on the self-recognition abilities of common ravens, (2) replicate results of azure-winged magpies, and (3) compare the mirror responses and performances in the mark test of these two corvid species with a third corvid species: carrion crows, previously tested following the same experimental procedure. Our results show interspecies differences in the approach of and the response to the mirror during the mirror exposure phase of the experiment as well as in the subsequent mark test. However, the performances of these species in the Mark Test do not provide any evidence for their ability of self-recognition. Our results add to the ongoing discussion about the convergent evolution of MSR and we advocate for consistent methodologies and procedures in comparing this ability across species to advance this discussion. [ABSTRACT FROM AUTHOR]

In the period 2018-2022, nesting of Common Raven (Corvus corax Linnaeus, 1758) pairs was established in the cities of Montana, Varshets and Sofia. In 2021, possible nesting was detected for one Common Raven pair in the city of Vratsa. [ABSTRACT FROM AUTHOR]

Background: Predator avoidance can have immense impacts on fitness, yet individual variation in the expression of anti-predator behaviour remains largely unexplained. Existing research investigating learning of novel predators has focused either on individuals or groups, but not both. Testing in individual settings allows evaluations of learning or personality differences, while testing in group settings makes it impossible to distinguish any such individual differences from social dynamics. In this study, we investigate the effect of social dynamics on individual anti-predator behaviour. We trained 15 captive ravens to recognize and respond to a novel experimental predator and then exposed them to this predator in both group and isolation settings across 1.5 years to tease apart individual differences from social effects and evaluate two hypotheses: (1) weaker anti-predator responses of some individuals in the group occurred, because they failed to recognize the experimental predator as a threat, leading to weak responses when separated, or (2) some individuals had learned the new threat, but their scolding intensity was repressed in the group trials due to social dynamics (such as dominance rank), leading to increased scolding intensity when alone. Results: We found that dominance significantly influences scolding behaviour in the group trials; top-ranked individuals scold more and earlier than lower ranking ones. However, in the separation trials scolding duration is no longer affected by rank. Conclusions: We speculate that, while top-ranked individuals use their anti-predator responses to signal status in the group, lower-ranking ravens may be suppressed from, or are less capable of, performing intense anti-predator behaviour while in the group. This suggests that, in addition to its recruitment or predator-deterrent effects, alarm calling may serve as a marker of individual quality to conspecifics. [ABSTRACT FROM AUTHOR]

The process of human decomposition is driven by biological decomposers, mainly bacteria, vertebrates, and invertebrate scavengers. When vertebrate scavengers have access to a body, they can considerably accelerate decomposition through consumption of soft tissue and dispersal of skeletal elements. Presently, there are limited data available on vertebrate scavenging activity in Canada, particularly in densely populated provinces such as Ontario. This study aimed to determine which vertebrate species belong to the scavenger guilds in central and northern Ontario, and the impact of season and habitat on these taphonomic agents. Seasonal trials were conducted in summer, fall, and spring of 2020/2021 with pig carcasses placed in open (grassland) and closed (forest) sites. Vertebrate scavenger activity was recorded continuously using cellular and non‐cellular trail cameras. Photographs were analyzed to identify species, quantify feeding intensity, and document scavenging behavior. We identified four mammalian scavengers, namely coyote, red fox, fisher, and pine marten, and three avian scavengers, namely bald eagle, turkey vulture, and American crows/northern ravens (grouped as corvids) across the trials. Season impacted scavenger presence with feeding and loss of soft tissue occurring more quickly in the summer, followed by spring and fall. None of the scavengers demonstrated a clear preference for the open versus closed sites. Our findings have identified the most prevalent vertebrate scavengers in central and northern Ontario and their taphonomic impact on soft and hard tissues. It is important to consider these agents and their ability to degrade and disperse remains during the search and recovery of human remains. [ABSTRACT FROM AUTHOR]

OBJECTIVE To determine the pharmacokinetics of voriconazole after single IV or orally administered boluses in common ravens (Corvus corax). ANIMALS 8 healthy common ravens. PROCEDURES Voriconazole (5 mg/mL, 10 mg/kg IV) was administered to 8 birds, and then plasma voriconazole concentrations were measured at various time points by high-pressure liquid chromatography with mass spectrometry. Starting 6 months later in a randomized 3-treatment 3-period regimen, birds received a single oral dose of voriconazole suspension (10 mg/mL; 6, 12, and 24 mg/kg PO). The study period was May 2015 to March 2016. RESULTS Voriconazole (10 mg/kg IV) achieved an initial plasma concentration of 6.31 µg/mL when measured over 21 hours. After oral administration of voriconazole at 6, 12, and 24 mg/kg, the relative bioavailability was 67.5%, 209%, and 183%, respectively. For the 6-mg/kg dose, the maximum plasma concentration was reached at 30 minutes after administration and remained in the therapeutic range of 0.5 to 1 µg/mL for approximately 15 hours. The 12- and 24-mg/kg doses resulted in concentrations in a potentially toxic range. CLINICAL RELEVANCE Voriconazole was well tolerated. All 4 doses resulted in plasma concentrations of voriconazole > 0.5 µg/mL, which is the minimum inhibitory concentration recommended for pathogenic species of Aspergillus fungi known to affect birds. A single dose of voriconazole administered as 10 mg/kg IV or 6 mg/kg PO resulted in recommended target plasma concentrations. Administration of voriconazole 6 mg/kg PO 2 to 3 times daily may be adequate for treatment without exceeding the toxic range. [ABSTRACT FROM AUTHOR]

Nest predation influences population dynamics and is thought to exert strong selection on the evolution of avian life history. Because parental behaviors can attract the attention of nest predators, incubating birds are predicted to decrease conspicuous behaviors at the nest-site and increase incubation constancy when risks of nest predation are high. We examined whether snowy plovers Charadrius nivosus responded to predator-specific risks of nest predation, using the number of off bouts and daily nest attendance (proportion of time spent incubating) as responses. We quantified risks using predator-specific hazard rates of nest mortality, which varied daily and were based on habitat characteristics at each nest. We assessed the influence of predator-specific risks of nest mortality on incubation behaviors using an individual-centering approach, allowing us to explain variation in incubation behaviors within- and among-breeding pairs. We found increased number of off bouts and nest attendance within-breeding pairs in response to increasing risks of nest predation by foxes (Vulpes spp.) and gulls (Larus spp.), but not coyotes (Canis latrans) and common ravens (Corvus corax). Among breeding pairs across habitats, we found increased nest attendance in response to higher risks of nest predation by foxes, but not coyotes, gulls, or ravens. Breeding pairs differed in the amount of behavioral plasticity they exhibited in response to risks of nest predation. Our results suggest that risks of nest predation differentially influence behavioral responses of snowy plovers depending on the predator species, and the amount of behavioral plasticity may depend on the characteristics of breeding adults. [ABSTRACT FROM AUTHOR]

Depredation by common ravens often exceeds stakeholders’ levels of acceptance. Common sources of excessive raven damage include loss of young livestock and nest depredation of species of concern, such as desert tortoise, greater sage-grouse, and least tern. USDA/APHIS Wildlife Services applies the avicide DRC-1339 (3-chloro-p-toluidine hydrochloride, CPTH) formulated in an intact-boiled egg bait to reduce such damage under the DRC-1339 Concentrate Livestock, Nest & Fodder Depredations label (EPA No. 56228-29). Although considered extremely effective on corvids, DRC-1339 is a slow acting toxicant and ravens may succumb away from the bait site, preventing the use of carcass recovery as a means to estimate take. To estimate take, Wildlife Services employs a model comprised of a bioenergetics module to predict consumption combined with a toxicological module that predicts mortality based on a probit analysis. This model has recently been revised to improve and standardize take estimates for common raven management activities using the egg baits covered by this label. Common ravens exhibit complex behaviors that impact the amount of bait consumed when offered DRC-1339 egg baits. The approaches to capturing this behavior in the model are presented along with take estimates associated with a range of baiting scenarios.

Background: Anthropogenic food sources (AFSs) are widespread in human-transformed landscapes and the current scale at which they occur drives ecological change at the individual, population, and community levels. AFSs are exploited extensively by common ravens, Corvus corax. Understanding how raven populations use AFSs can provide insight into their ecological responses to AFSs. Methods: We equipped 81 ravens in the Austrian Alps with GPS-transmitters over a period of 2.75 years. Using these tracking data, we investigated how cohort differences (i.e., age, sex, and origin) and seasonal changes influence raven movement patterns (i.e., occurrence distribution and maximum daily displacement) and AFS-use (i.e., number of AFSs visited and probability of being present at any AFS) at 45 extensively exploited sites. Results: We found that proxies for experience and dominance, inferred by age (i.e., juvenile versus adult) and origin (i.e., wild-caught versus captive-bred-released) cohorts, influenced movement patterns and the number of AFSs visited. However, all individuals were equally likely to be present at AFSs, highlighting the importance of AFSs for non-breeders in the study population. Seasonal changes in environmental conditions that affect energetic demands, the availability of natural and anthropogenic food, and foraging competition, influenced individuals' occurrence distributions and AFS-use. We found that under harsher conditions in autumn and winter, individuals ranged wider and depended on AFSs to a larger degree. However, contrary to expectation, they were less likely to be present at AFSs in these seasons compared to spring and summer, suggesting a trade-off between time spent moving and exploiting resources. We attribute the small ranging movements exhibited by non-breeders in spring and summer to the presence of highly territorial and socially dominant breeders. As breeders mostly stay and forage within their territories during these seasons, competition at AFSs decrease, thereby increasing the likelihood of individuals being present at any AFS. Conclusions: We emphasize that movement and AFS-use differ according to cohort differences and the seasonality of the environment. Our results highlight that predictable AFSs affect foraging strategies among non-breeding ravens. The extent of AFS-exploitation among non-breeding ravens in our study emphasize the potential of AFSs in shaping raven movement and resource-use. [ABSTRACT FROM AUTHOR]

Simple Summary: Modern evolutionary biology offers a wide variety of methods to explore the evolution of species and to describe their relationships. The methods of DNA/RNA sequence analysis have been developing for decades and have become increasingly popular and reasonably reliable. Nevertheless, final phylogenetic trees for many taxa are still under debate because both classical and genomics-based approaches have their own limitations for phylogenetic tree reconstruction. Here, we propose the use of younger 'omics' methods, namely quantitative metabolomics, to aid the phylogeny reconstruction of vertebrates. We show that metabolomics-based hierarchical clustering analysis trees match, although not perfectly, to the genomics-based trees. In the current pilot study, we propose the use of quantitative metabolomics to reconstruct the phylogeny of vertebrates, namely birds. We determined the concentrations of the 67 most abundant metabolites in the eye lenses of the following 14 species from 6 orders of the class Aves (Birds): the Black kite (Milvus migrans), Eurasian magpie (Pica pica), Northern raven (Corvus corax), Eurasian coot (Fulica atra), Godlewski's bunting (Emberiza godlewskii), Great crested grebe (Podiceps cristatus), Great tit (Parus major), Hawfinch (Coccothraustes coccothraustes), Hooded crow (Corvus cornix), House sparrow (Passer domesticus), Rock dove (Columba livia), Rook (Corvus frugilegus), Short-eared owl (Asio flammeus) and Ural owl (Strix uralensis). Further analysis shows that the statistical approaches generally used in metabolomics can be applied for differentiation between species, and the most fruitful results were obtained with hierarchical clustering analysis (HCA). We observed the grouping of conspecific samples independently of the sampling place and date. The HCA tree structure supports the key role of genomics in the formation of the lens metabolome, but it also indicates the influence of the species lifestyle. A combination of genomics-based and metabolomics-based phylogeny could potentially resolve arising issues and yield a more reliable tree of life. [ABSTRACT FROM AUTHOR]

Simple Summary: Research suggests that contagious yawning evolved to synchronize activity and vigilance within groups. To date, yawning has shown to be contagious in a wide range of mammalian species, including humans, great apes, some monkey species, domesticated dogs and pigs, wolves, lions, and rats. However, yawn contagion has only been previously documented in one bird species: budgerigars (Melosittacus undulatus). Here, we sought to examine whether yawning was contagious among juvenile common ravens (Corvus corax). By observing two small and undisturbed captive groups, we also assessed the contagious nature of other frequently observed and potentially contagious behaviors: stretching, scratching, and shaking. Overall, we found no evidence for behavioral contagion. Given the limitations to the observational methods, however, we suggest future experimental research be conducted to support these findings. The overt and reflexive matching of behaviors among conspecifics has been observed in a growing number of social vertebrates, including avian species. In general, behavioral contagion—such as the spread of yawning—may serve important functions in group synchronization and vigilance behavior. Here, we performed an exploratory study to investigate yawn contagion among 10 captive juvenile ravens (Corvus corax), across two groups. Using observational methods, we also examined the contagiousness of three other distinct behaviors: stretching, scratching, and shaking. A total of 44 20 min observations were made across both groups, including 28 in the morning and 16 in the afternoon. The time and occurrence of all the behaviors from each bird were coded, and the temporal pattern of each behavior across both groups was then analyzed to assess the degree of social contagion. Overall, we found no evidence for contagious yawning, stretching, scratching, or shaking. However, yawns were relatively infrequent per observation (0.052 ± 0.076 yawns/bird) and thus experimental methods should be used to support this finding. [ABSTRACT FROM AUTHOR]

The classic paper by Ehrlich and Raven on coevolution will soon be 60 years old. Although they were not the first to develop the idea of coevolution, their thought‐provoking paper certainly popularized this idea and inspired several generations of scientists interested in coevolution. Here, we describe some of their main contributions, quantitatively measure the impact of their seminal paper on different fields of research, and discuss how ideas related to their original paper might push the study of coevolution forward. To guide our discussion, we explore their original hypothesis into three research fields that are associated with distinct scales/levels of organization: (1) the genetic mechanisms underlying coevolutionary interactions; (2) the potential association between coevolutionary diversification and the organization of ecological networks; and (3) the micro‐ and macroevolutionary mechanisms and expected patterns under their hypothesis. By doing so, we discuss potentially overlooked aspects and future directions for the study of coevolutionary dynamics and diversification. [ABSTRACT FROM AUTHOR]

Subsidization of predator populations increases predation pressure on prey species, which is exacerbated when natural resources are scarce. Estimating the frequency of predation by subsidized predators on vulnerable species, especially low‐density, long‐lived species such as the federally threatened Mojave desert tortoise (Gopherus agassizii), allows landscape managers to evaluate the need for actions like reducing subsidies, discouraging predation by taste aversion, or predator removal. Most studies of Mojave desert tortoise predation have relied on morphological analysis to identify hard parts in predator scat. Here, we developed and validated a qPCR assay to test for the presence of Mojave desert tortoise in DNA extracted from scat and pellets. We used the assay to detect tortoise DNA in scat and pellets collected in a conservation easement adjacent to Boulder City, Nevada, from three Mojave desert tortoise predators: coyotes (Canis latrans), desert kit foxes (Vulpes macrotis arsipus), and common ravens (Corvus corax)—all of which consume anthropogenic resources. We compared the results of our qPCR assay to results from morphological analysis of the same samples and found that the qPCR method is much more sensitive at detecting the presence of tortoise remains. Although neither method can determine whether consumption was the result of predation or scavenging, nor how many individual tortoises were consumed, our findings indicate that conservation managers may benefit from focusing efforts on reducing subsidies that attract and support predators and on reducing tortoise mortality from predation. [ABSTRACT FROM AUTHOR]

Common ravens (Corvus corax) inhabited much of the eastern United States prior to European colonization but were nearly extirpated by the mid‐1900s. Although remnant raven populations have since begun recolonizing portions of their historic range in the eastern United States, the extent of recovery remains largely unknown because of the species' elusive behavior. To aid development of targeted monitoring programs for this rare and cryptic species, we investigated factors that may influence detectability of ravens in natural cliff habitat during the nesting season in the Central Appalachian Mountains. Using a time‐to‐detection framework, we performed surveys at cliff sites with positive raven occupancy and recorded time to first detection (TFD) and confirmed cliff occupancy (i.e., occupied detection) to estimate detection probability curves as a function of survey time. We further compared multiscale habitat features of occupied and unoccupied cliff sites to characterize regional nesting habitat. Mean TFD at occupied cliffs was 14 ± 2 (SE) min. The TFD and subsequent detection probability increased with warming temperatures, likely as a result of heightened activity at nests as the reproductive season progressed. Shorter distances from observation point to the surveyed cliff resulted in longer TFD, indicating that ravens are likely sensitive to disturbance at nest sites. Analysis of cliff‐nesting habitat data identified raven selection of cliffs with large, exposed faces positioned on predominant west‐facing aspects. Mean detection probability calculated from detectability curves was ≥0.8 after the first 30 min. Using a probability‐based model and empirical detection probabilities, we estimated that raven absence from a cliff site during the nesting season may be inferred with p = 0.99 after three independent 30‐min surveys. Although ravens have been considered elusive and rare in the eastern United States, we find that their detectability at occupied cliff sites during the nesting season is relatively high and that observation of distributional changes may be easier for this species than for other, more cryptic birds. [ABSTRACT FROM AUTHOR]

The article titled "Vocalizations Help Distinguish Male and Female Brown-Headed Nuthatches (Sitta pusilla) in the Field" discusses the discovery of sex-based vocalizations in the Brown-Headed Nuthatch, a cooperatively breeding species found in mature pine forests of the southeastern United States. The researchers have observed distinct vocalizations that can be used to differentiate between males and females in the field. Female nuthatches produce higher-pitched serial vocalizations with frequent peeps and multiple-syllable twitters, while male vocalizations lack these characteristics. This finding provides valuable insights into the behavior and ecology of this species and highlights the benefits of long-term field studies. [Extracted from the article]

Simple random-sampling resolutions of the raven paradox relevantly diverge from scientific practice. We develop a stratified random-sampling model, yielding a better fit and apparently rehabilitating simple random sampling as a legitimate idealization. However, neither accommodates a second concern, the objection from potential bias. We develop a third model that crucially invokes causal considerations, yielding a novel resolution that handles both concerns. This approach resembles Inference to the Best Explanation (IBE) and relates the generalization's confirmation to confirmation of an associated law. We give it an objective Bayesian formalization and discuss the compatibility of Bayesianism and IBE. [ABSTRACT FROM AUTHOR]

A main goal of seabird colony restoration is for the colony to become self-sustaining. To do so, elevated rates must be attained in (1) reproductive success and (2) recruitment by immigrants and birds produced at the colony. Thus, an understanding of the factors affecting reproductive success and recruitment at restoration sites is vital. We examined how spatial features at the colony level affected reproductive success of Common Murres Uria aalge (hereafter, murres) over a six-year period at Devil's Slide Rock, California, a colony re-established using social attraction techniques. Clusters of sites with similar egg-laying dates, as well as high hatching and breeding success, occurred in the densest portion of the colony, which was also the last area occupied by murres at the time of extirpation and the first area to be re-colonized. Clusters of sites with low success occurred in outlying, low-density portions of the colony. Breeding success, influenced largely by high fledging success, averaged > 60% most years. Reproductive success was greatest at breeding sites with earlier egg-laying dates, those in closest proximity to the breeding sites of other murres and the Brandt's Cormorant Urile penicillatus, and those outside Brown Pelican Pelecanus occidentalis disturbance zones. Based on our findings, for future murre restoration projects in the California Current System, we suggest (1) placing social attraction equipment in the area(s) last utilized by murres prior to extirpation, (2) attempting to establish two dense breeding groups, (3) targeting sites already utilized regularly by nesting Brandt's Cormorants, and (4) avoiding sites or habitats prone to disturbance by larger and aggressive species such as Brown Pelicans, Bald Eagles Haliaeetus leucocephalus, or Common Ravens Corvus corax. [ABSTRACT FROM AUTHOR]

Dominance hierarchies typically emerge in systems where group members regularly encounter and compete for resources. In birds, the ‘open’ and dynamic structure of foraging groups may prevent the emergence of structured hierarchies, although this assumption have hardly been tested. We report on agonistic data for ravens Corvus corax, collected over two 18-month periods for 183 marked individuals of a wild (fluid) population and 51 birds from six captive (stable) groups. We show that the dominance structure (steep and transitive) in wild foraging groups is strikingly similar to that found in captivity. In the wild, we found that higher ranks are mainly occupied by males, older and more aggressive individuals that also tend to receive fewer aggressions. Exploring the mechanisms sustaining the wild dominance structure, we confirmed that males are more aggressive than females and, with age, tend to receive fewer aggressions than females. Males that are about to leave the foraging groups for some months are less aggressive than newcomers or locals, while newcomers are specifically targeted by aggressions in their first year (as juveniles). Taken together, our results indicate that the socially dynamic conditions ravens face during foraging do not hinder, but provide opportunities for, using (advanced) social cognition. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

Although three species of Sarcocystis, S. cornixi, S. corvusi and S. kutkienae, have been described in corvids, molecular studies of sarcocysts isolated from these birds are incomplete. Leg muscles of 83 corvids, 35 hooded crows (Corvus cornix), 21 western jackdaws (Coloeus monedula), 11 rooks (Corvus frugilegus), 9 common ravens (Corvus corax), 4 common magpies (Pica pica) and 3 Eurasian jays (Garrulus glandarius), from Lithuania were examined for the presence of Sarcocystis spp. in the present study. In methylene blue–stained squashed samples, sarcocysts were detected in 26 birds (31.0%). Under a light microscope, two morphological types of sarcocysts were distinguished (type A and type B). Sarcocysts of type A had a smooth and thin (about 1 μm) cyst wall, while cysts of type B were characterised by a thicker (1.4–2.5 μm) cyst wall. Based on ITS1 sequence comparison, sarcocysts of type A were identified as S. halieti and Sarcocystis sp. ex Corvus corax, whereas cysts of type B belonged to S. kutkienae and S. cornixi. Furthermore, it was demonstrated that a single bird could host two different Sarcocystis spp. Sarcocystis halieti was detected in corvids for the first time in the common raven and the hooded crow. Also, this study presents the first evidence of S. kutkienae in the hooded crow and the common magpie, and S. cornixi in the western jackdaw. Sarcocystis sp. ex Corvus corax was genetically characterised using almost complete 18S rDNA, partial 28S rDNA and complete ITS1 sequences. Sarcocystis sp. ex Corvus corax clustered together with S. columbae, S. corvusi and S. halieti in phylogenetic trees reconstructed using 28S rDNA and ITS1 sequences. [ABSTRACT FROM AUTHOR]