Corvus Corone Research Articles

Large-scale correlations between gamebird release and management and animal biodiversity metrics in lowland Great Britain.

The ecological effects on populations of non-game species driven by the annual release and management of tens of millions of gamebirds for recreational shooting are complex and relatively poorly understood. We investigated these effects at a national scale, considering multiple taxa simultaneously. We used records from the UK National Biodiversity Network Atlas to compare animal species and diversity metrics previously suggested to be affected by behaviors of the released birds, or because resources or habitats are influenced by game management or both processes. We contrasted records from 1 km grid squares where gamebirds were reported released in Great Britain, and control squares with similar land cover but where no releases were reported. There were more records overall reported from release grid squares (RGS) compared with controls (CGS), perhaps due to greater reporting effort or greater biological richness. We found fewer foxes in RGS and fewest in grid squares with largest releases, but more carrion crows in RGS. We found no consistent effects for buzzards, ravens, jays, or magpies. There were more rodents and gray squirrels reported from RGS but no differences for reptiles. There were more butterflies but fewer beetles reported from RGS but no consistent patterns for Orthoptera or ground beetles considered common gamebird prey. Farmland and woodland birds exhibited higher abundance, richness, and diversity in RGS when considering absolute records, but woodland bird abundance and richness were lower when correcting for the relative number of records. These nationwide results, despite crude data resolution, reveal diverse effects of gamebird release and management at a national scale and across trophic levels, increasing some non-game animal populations while decreasing others. This should alert practitioners, opponents, and legislators that a focus on single taxa effects, either positive or negative, may obscure the simultaneous changes in other taxa.

Wild Carrion Crows (Corvus corone) Autonomously Respond to Speech but Show No Difference in Their Response to a Local and a Foreign Language

Eavesdropping on the vocalizations of other species can be beneficial for wildlife to avoid predator encounters, including encounters with humans. Wild-caught large-billed crows in Tokyo responded more to playback of a foreign language than to Japanese without any training or rewards provided in the experiment, suggesting habituation to the local language. Here I tested the response of wild carrion crows in the UK to playback of a foreign language (Vietnamese), the local language (English), and non-speech control vocalizations (pigeon and parakeet vocalizations) to examine whether wild crows eavesdrop on speech. Playback experiments were conducted in two cities that differ in their population size and linguistic diversity (London and Milton Keynes, Buckinghamshire), to understand the role of exposure frequency to humans and to different languages in their response to speech. The crows autonomously responded with increased flight behaviors to human speech compared to non-speech control vocalizations. However, unlike previously shown for large-billed crows, the carrion crows did not respond differently to the two languages. It remains to be understood whether eavesdropping on speech provides any benefit to the animals, particularly urban individuals with frequent exposure to humans.

Crows protect visual working memory against interference.

Working memory, the ability to actively maintain and manipulate information across time, is key to intelligent behavior. Because of the limited capacity of working memory, relevant information needs to be protected against distracting representations. Whether birds can resist distractors and safeguard memorized relevant information is unclear. We trained carrion crows in a delayed match-to-sample task to memorize an image while resisting other, interfering stimuli. We found that the repetition of the sample stimulus during the memory delay improved performance accuracy and accelerated reaction time relative to a reference condition with a neutral interfering stimulus. In contrast, the presentation of the image that constituted the subsequent non-match test stimulus mildly weakened performance. However, the crows' robust performance in this most demanding distractor condition indicates that sample information was actively protected from being overwritten by the distractor. These data show that crows can cognitively control and safeguard behaviorally relevant working memory contents.

Varying response of breeding waders to experimental manipulation of their habitat and predators

Many ground-nesting bird species including waders are of conservation concern across Europe. Population declines of Eurasian Curlew Numenius arquata (hereafter Curlew), a globally Near-threatened wader, exemplify this and are driven by low breeding success due to predation, and loss and degradation of breeding habitat. We tested whether the combined delivery of vegetation management and lethal control of Red Foxes Vulpes vulpes and Carrion Crows Corvus corone and Hooded Crows C. cornix improved Curlew nesting success and breeding abundance across UK study sites over five years. On trial sites, vegetation management improved habitat condition and Curlew distributions shifted towards managed areas. However, changes in predator abundances, Curlew nesting success and Curlew breeding abundance did not differ between trial and reference sites. Northern Lapwing Vanellus vanellus numbers increased on trial sites and decreased on reference sites, whilst Common Snipe Gallinago gallinago numbers showed no treatment response. Some of these outcomes were associated with additional environmental variables added to Treatment:Year terms in three-way interactions (changes in fox abundance associated with abundance of non-native gamebirds; changes in Crow abundance associated with gamebirds and woodland area; changes in Curlew nesting success associated with crow abundance), highlighting that outcomes depend on site-specific contexts, and consistent responses to interventions cannot be assumed. The difficulty in increasing Curlew nesting success likely relates to underlying mesopredator densities in the UK, which are known to be high in a European context. Our results suggest that a model of delivery like this study, including management of predators using lethal control, at comparable intensities, is highly unlikely to be effective for Curlew or Snipe within agri-environment schemes, but could be for Northern Lapwing. To make progress on wader recovery it is imperative to understand the underlying drivers of high mesopredator densities and address these through landscape-scale intervention and policy changes.

Изменение структуры населения птиц под воздействием антропогенных факторов в долине р. Угам (Западный Тянь-Шань)

The article addresses the issues of changes in the species composition and number of birds in the middle part of the valley of the Ugam River. The valley has been mastered by humans since ancient times, but due to its geographical location, the possibilities for conducting economic activities in it have always been limited, and its intensity has its own characteristics. Here, the location of the only settlement changed, orchards were planted and cut down, cattle were grazed everywhere or in the vicinity of the village, hayfields were mowed or abandoned, and field roads were laid and overgrown. The inclusion of the territory in the Sairam-Ugam National Park has reoriented human activities. The construction of tourist facilities has begun and continues here, which has led to an increase in the number of lovers of outdoor recreation. All this was reflected in the birds of the valley, which are very sensitive to environmental changes. This is especially noticeable in mountainous conditions, where the concentration of nesting species is not high, the main routes of migrants go along the foothills, and wintering conditions are not favorable. The first data on the avifauna of this section of the valley were obtained by M.N. Korelov in the summer and autumn of 1949 and later collected by the author in May 2003, July 2011, and 2022, which made it possible to analyse its species-specific variation. Over 70 years of observations, 127 bird species were encountered here, of which 114 were in 1949, 53 were in 2003, 54 were in 2011, and 44 were in 2022. The structure of the bird population in the valley also changed. This is especially noticeable in July 2003 and 2022, when the studies were carried out on the same days. In the first year, human activity was limited to the outskirts of the village, and in the second year, it was carried out throughout the entire section of the valley. In the first year, 617 individuals were encountered in 4 days; in the second year, 307, i.e., twice as small. In 2003, the main bird populations were Corvus corone (11.4% of the number of birds encountered), Pica pica (11.2%), Emberiza bruniceps (9.4%), Acridotheres tristis (7.3%), Emberiza cia (6.6%), Lanius minor (5.7%) and Carduelis caniceps (5.3%), and in 2022, Chloris chloris (12.4%), Ac. tristis (12.1%), C. caniceps (11.4%), Streptopelia orientalis (6.6%), C. corone (4.5%), P. pica and Em. bruniceps (3.8% each). With the development of the valley by humans, the species ratio of birds also changed. In 1949, species whose life is exclusively associated with humans were not recorded here; in 2003, 2011, and 2022, they included 5 species (Columba livia, Streptopelia senegalensis, Hirundo rustica, H. daurica, and Acridotheres tristis), which accounted for 14.2, 29.0, and 10.3% of the number of individuals encountered, respectively. The number of species indifferent to the place of residence, but preferring natural biotopes, has been stable over the years - 16, 17, 15 and 16, but changed quantitatively (50.0, 31.1 and 45.7% in 2003, 2011 and 2022). During the same period, the diversity of species living in natural biotopes also decreased (32, 27, and 25). All these and other issues are discussed in the analysis of each bird species, and it is shown that the increased anthropotization of the valley leads to a reduction in species diversity, the number of birds living here and to the loss of its uniqueness.

Результаты первой попытки привлечения пары орлана-белохвоста в искусственное гнездовье

Результаты первой попытки привлечения пары орлана-белохвоста в искусственное гнездовье

Anything for a quiet life: shelter from mobbers drives reproductive success in a top‐level avian predator

Understanding how habitat structure relates to reproductive performance of species can help identify what habitats are of the highest quality for a given species and thereby guide effective management. Here, we compared the influence of prey abundance and the amount of shelter area on the relationship between habitat and breeding performance. We focused on the forest‐dwelling northern goshawkAccipiter gentilisin an agroforestry system. Using structural equation modelling, we tested the associations between reproductive performance and three explanatory factors: habitat structure, abundance of food resources or levels of mobbing disturbance, and prey supply to the nest. Our results suggest that habitat structure influences reproductive performance through shelter rather than through prey abundance. During the study period, forested habitats in the breeding territories provided shelter to the goshawk, reducing disturbance by carrion crowsCorvus corone, which acted as large, aggressive, social mobbers. Decreased disturbance increased prey supply to the nest, probably because it favored food accessibility and male goshawk foraging efficiency. Habitat was not significantly associated with quality of the breeders, both in terms of body size and seniority in the territories. Our findings suggest that reproductive performance, and therefore habitat quality, may depend more on sheltered access to food resources than on the amount of food available. Our observation that mobbers decrease predator foraging efficiency highlights the possibility of designing effective, socially acceptable predator management strategies to protect sensitive domestic prey.

Copulations with a nestling by an adult care-giver in a kin-living bird

Abstract Adult sexual interest in dependent young, such as lactating pups or nestlings, has been reported in a few species, with copulations with related dependent young being, at best, extremely rare. Here we document two events of copulations on a nestling by an adult caregiver in a group of kin-living and cooperatively breeding carrion crows Corvus corone. Copulations, as well as other unusual rough actions toward the nestling, occurred within a short time-span characterized by intense conflict among adult group members, suggesting that stress could trigger such behaviours toward the brood.

Exogenous and endogenous spatial attention in crows

Attention describes the ability to selectively process a particular aspect of the environment at the expense of others. Despite the significance of selective processing, the types and scopes of attentional mechanisms in nonprimate species remain underexplored. We trained four carrion crows in Posner spatial cueing tasks using two separate protocols where the attention-capturing cues are shown at different times before target onset at either the same or a different location as the impending target. To probe automatic bottom-up, or exogenous, attention, two naïve crows were tested with a cue that had no predictive value concerning the location of the subsequent target. To examine volitional top-down, or endogenous, attention, the other two crows were tested with the previously learned cues that predicted the impending target location. Comparing the performance for valid (cue and target at same location) and invalid (cue and target at opposing locations) cues in the nonpredictive cue condition showed a transient, mild reaction time advantage signifying exogenous attention. In contrast, there was a strong and long-lasting performance advantage for the valid conditions with predictive cues indicating endogenous attention. Together, these results demonstrate that crows possess two different attention mechanisms (exogenous and endogenous). These findings signify that crows possess a substantial attentional capacity and robust cognitive control over attention allocation.

A comparative study of mirror self-recognition in three corvid species

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.

A brain atlas of the carrion crow (Corvus corone).

Corvidae, passerine songbirds such as jays, crows, and ravens known as corvids, have become model systems for the study of avian cognition. The superior cognitive capabilities of corvids mainly emerge from a disproportionally large telencephalon found in these species. However, a systematic mapping of the neuroanatomy of the corvid brain, and the telencephalon in particular, is lacking so far. Here, we present a brain atlas of the carrion crow, Corvus corone, with special emphasis on the telencephalic pallium. We applied four staining techniques to brain slices (Nissl, myelin, combination of Nissl and myelin, and tyrosine hydroxylase targeting catecholaminergic neurons). This allowed us to identify brain nuclei throughout the brain and delineate the known pallial subdivisions termed hyperpallium, entopallium, mesopallium, nidopallium, arcopallium, and hippocampal complex. The extent of these subdivisions and brain nuclei are described according to stereotaxic coordinates. In addition, 3D depictions of pallial regions were reconstructed from these slices. While the overall organization of the carrion crow's brain matches other songbird brains, the relative proportions and expansions of associative pallial areas differ considerably in agreement with enhanced cognitive skills found in corvids. The presented global organization of the crow brain in stereotaxic coordinates will help to guide future neurobiological studies in corvids.

Colouration and flavouring of sunflower seeds affect feeding behaviour in urban Carrion crows (Corvus corone): A preliminary study

The damage caused to crops by wildlife, particularly birds, represent a major challenge for farmers. This study aimed to preliminarily assess feeding behaviour of Carrion crows (Corvus corone) on sunflower seeds in field conditions. The crows’ preferences were tested along a visual cue (seed colour: blue vs. uncoloured) and a taste cue (pepper coating vs. unflavoured). The experiments were carried out in two sessions interspersed by several weeks. For each session, the influence of seed colours on birds’ preferences (n = 200 uncoloured, n = 200 blue) was assessed on day 1, and the influence of seed pepper coating (n = 200 pepper coated, n = 200 unflavoured seeds) was assessed on days 2 and 3. Every day, the remaining seeds within each furrow were counted at 4 after the start of the assay. Throughout the experiments, the only wild birds seen consuming seeds were Carrion crows (Corvus corone). In each session, the birds consumed significantly less blue seeds than controls (p < 0.05). However, blue seed intake significantly increased between the 2 sessions. The birds thus appear to rely on sight to select sunflower seeds. Otherwise, a significant effect of pepper coating arose in session 2, with birds consuming less pepper-coated seeds than unflavoured seeds (p < 0.0001). This intake of pepper seeds was significantly higher in session 1 than in session 2. Therefore, coating the seeds with a pungent irritant may induce reluctance. These assays confirm that Carrion crows are sensitive to the colour and flavour of sunflower seeds, rapidly learn and get used to visual and chemosensory novelty.

Predation of Greylag Goose (Anser anser) gosling by Carrion Crow (Corvus corone corone)

Evidence of avian predation on Greylag Goose (Anser anser) goslings is generally inferential. Here, we report an observation of a Carrion Crow (Corvus corone corone) preying on a gosling in Port Meadow, Oxford, United Kingdom. Our observation demonstrates that, in addition to being an egg predator, Carrion Crows are opportunistic predators of Greylag Goose goslings. To our knowledge, this is the first time that this interaction has been documented in the literature.

Contrasting effects of eucalyptus, pine and oak plantations on nest predation risk in Mediterranean grasslands

Large scale afforestation (i.e., establishment of forests on farmland, grassland and other land not previously forested) is increasingly regarded as a cost-effective option to mitigate climate change by promoting carbon sequestration. However, this strategy can have negative biodiversity impacts, potentially causing the loss and fragmentation of open habitats of conservation value, as well as edge effects that can extend well beyond forest boundaries. Mitigating impacts of afforestation programs thus requires a detailed understanding of the mechanisms whereby they affect biodiversity, particularly where new plantations are established close to areas important for open habitat species. Here, we examined how afforestation with oak, pine or eucalyptus trees, commonly planted in Mediterranean Europe, may have distinct effects on nest predation risk of grassland birds in southern Portugal. We used artificial nests with quail eggs and camera traps to: (i) identify nest predators and estimate predation risk of ground-nesting birds in grasslands adjacent to oak, pine and eucalyptus plantations across a distance gradient (0 m to 300 m) from the plantation edge; and (ii) examine how predation risk was influenced by avian predator abundance, sward height and vegetation clearing for photo-monitoring (nest-site manipulation), and their interactions with plantation type. Carrion crow was by far the main egg predator identified, followed by Montagu’s harrier, raven and magpie. Overall, nest predation risk and predator abundance were higher around eucalyptus plantations, compared to either pine or oak plantations. Predation decreased with increasing sward height, but this effect was less noticeable when vegetation around nests was cleared. In pine and oak plantations, predation risk was slightly higher close to edges, and decreased with distance from the edge. Conversely, in eucalyptus plantations predation was lower close to edges, and increased with distance to edges. Distance effects around eucalyptus plantation were, however, absent in manipulated nests. Overall, results show that afforestation with different tree species has distinct impacts on predation risk of artificial nests in Mediterranean farmland. This is probably a consequence of an increasing structural complexity of the plantations, from oak to eucalyptus, driven by differences in tree growth rates and undergrowth cover. These findings suggest that farmland afforestation should favour agro-forest plantations with slow growing species (oak and pine) to mitigate negative effects on breeding grassland birds in adjacent open habitats.

Accumulation and ineffective silencing of transposable elements on an avian W Chromosome.

One of the defining features of transposable elements (TEs) is their ability to move to new locations in the host genome. To minimize the potentially deleterious effects of de novo TE insertions, hosts have evolved several mechanisms to control TE activity, including recombination-mediated removal and epigenetic silencing; however, increasing evidence suggests that silencing of TEs is often incomplete. The crow family experienced a recent radiation of LTR retrotransposons (LTRs), offering an opportunity to gain insight into the regulatory control of young, potentially still active TEs. We quantified the abundance of TE-derived transcripts across several tissues in 15 Eurasian crows (Corvus (corone) spp.) raised under common garden conditions and find evidence for ineffective TE suppression on the female-specific W Chromosome. Using RNA-seq data, we show that ∼9.5% of all transcribed TEs had considerably greater (average, 16-fold) transcript abundance in female crows and that >85% of these female-biased TEs originated on the W Chromosome. After accounting for differences in TE density among chromosomal classes, W-linked TEs were significantly more highly expressed than TEs residing on other chromosomes, consistent with ineffective silencing on the former. Together, our results suggest that the crow W Chromosome acts as a source of transcriptionally active TEs, with possible negative fitness consequences for female birds analogous to Drosophila (an X/Y system), in which overexpression of Y-linked TEs is associated with male-specific aging and fitness loss (“toxic Y”).

Assortative mating and epistatic mating-trait architecture induce complex movement of the crow hybrid zone.

Hybrid zones provide a window into the evolutionary processes governing species divergence. Yet, the contribution of mate choice to the temporal and spatial stability of hybrid zones remains poorly explored. Here, we investigate the effects of assortative mating on hybrid-zone dynamics by means of a mathematical model parameterized with phenotype and genotype data from the hybrid zone between all-black carrion and gray-coated hooded crows. In the best-fit model, narrow clines of the two mating-trait loci were maintained by a moderate degree of assortative mating inducing pre- and postzygotic isolation via positive frequency-dependent selection. Epistasis between the two loci induced hybrid-zone movement in favor of alleles conveying dark plumage followed by a shift in the opposite direction favoring gray-coated phenotypes 200generations after secondary contact. Unlinked neutral loci diffused near-unimpeded across the zone. These results were generally robust to the choice of matching rule (self-referencing or parental imprinting) and effects of genetic drift. Overall, this study illustrates under which conditions assortative mating can maintain steep clines in mating-trait loci without generalizing to genome-wide reproductive isolation. It further emphasizes the importance of the genetic mating-trait architecture for spatio-temporal hybrid-zonedynamics.

Behavioral Responses of Captive Corvids to the Presence of Visitors

Behavioral responses of captive animals to the presence of visitors in zoos and wildlife parks can be interpreted as signs of negative (disturbance), neutral or positive (enrichment) welfare. In the present study, we investigated behavioral responses of captive common ravens, Corvus corax and crows, Corvus corone, to the presence of visitors in general and to the proximity or distance of visitors to the aviary respectively. Duration of affiliative behaviors, feeding and stress-related behaviors did not change when visitors were present compared to control situations without visitors being present. Both corvid species showed less head up behavior when visitors were in sight compared to the control condition. In contrast, preening of crows significantly increased when visitors were within two meters of the aviary compared to the control condition. The same relationship was found in regard to increase in vocalization for common ravens, but not for crows. Our results indicate that corvids, housed in a wildlife park for several years, still show behavioral responses to the presence of human visitors in close proximity to their enclosure. Overall, we did not find clear indications for reduced welfare due to visitor presence, such as increased locomotion or stress-related behaviors. We therefore conclude that the described behavioral changes are not indicative of any negative welfare impacts of visitor presence.

Niveurmôrre: Versions françaises du “Corbeau” au XIXe siècle

Niveurmôrre: Versions françaises du “Corbeau” au XIXe siècle

Potential of Cassia alata and Cassia multijuga to Phytoremediate Mined-out Soils in the Puruni Mining Area

Phytoremediation is a technology that uses plants to remove contaminants such as mercury from soil. This research examined phytoremediation as an option to remove mercury from mined out soils in the Puruni mining area, Mazaruni (Region VII). The study examined the phytoextractive capabilities of the Cassia alata (Carrion Crow Bush) and Cassia multijuga (False Sicklepod). Soil sampling was conducted to determine mercury levels at five mined out sites: Jubilee Creek Nos. 1 &amp; 2, Chinese Creek, Tiger Creek, and the Takatu area. A tube auger and sieve were used to extract soil samples and remove debris.

Learning and motor inhibitory control in crows and domestic chickens.

Cognitive abilities allow animals to navigate through complex, fluctuating environments. In the present study, we tested the performance of a captive group of eight crows, Corvus corone and 10 domestic chickens, Gallus gallus domesticus, in the cylinder task, as a test of motor inhibitory control and reversal learning as a measure of learning ability and behavioural flexibility. Four crows and nine chickens completed the cylinder task, eight crows and six chickens completed the reversal learning experiment. Crows performed better in the cylinder task compared with chickens. In the reversal learning experiment, species did not significantly differ in the number of trials until the learning criterion was reached. The performance in the reversal learning experiment did not correlate with performance in the cylinder task in chickens. Our results suggest crows to possess better motor inhibitory control compared with chickens. By contrast, learning performance in a reversal learning task did not differ between the species, indicating similar levels of behavioural flexibility. Interestingly, we describe notable individual differences in performance. We stress the importance not only to compare cognitive performance between species but also between individuals of the same species when investigating the evolution of cognitive skills.