Corvus Corone Research Articles

Enterococcus faecalis provides protection during scavenging in carrion crow ( Corvus corone).

The gut microbiota significantly influences host physiology and provides essential ecosystem services. While diet can affect the composition of the gut microbiota, the gut microbiota can also help the host adapt to specific dietary habits. The carrion crow ( Corvus corone), an urban facultative scavenger bird, hosts an abundance of pathogens due to its scavenging behavior. Despite this, carrion crows infrequently exhibit illness, a phenomenon related to their unique physiological adaptability. At present, however, the role of the gut microbiota remains incompletely understood. In this study, we performed a comparative analysis using 16S rRNA amplicon sequencing technology to assess colonic content in carrion crows and 16 other bird species with different diets in Beijing, China. Our findings revealed that the dominant gut microbiota in carrion crows was primarily composed of Proteobacteria (75.51%) and Firmicutes (22.37%). Significant differences were observed in the relative abundance of Enterococcus faecalis among groups, highlighting its potential as a biomarker of facultative scavenging behavior in carrion crows. Subsequently, E. faecalis isolated from carrion crows was transplanted into model mice to explore the protective effects of this bacterial community against Salmonella enterica infection. Results showed that E. faecalis down-regulated the expression of pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and interleukin 6 (IL-6), prevented S. enterica colonization, and regulated the composition of gut microbiota in mice, thereby modulating the host's immune regulatory capacity. Therefore, E. faecalis exerts immunoregulatory and anti-pathogenic functions in carrion crows engaged in scavenging behavior, offering a representative case of how the gut microbiota contributes to the protection of hosts with specialized diets.

Animal-sourced model of human norovirus infection predicted using environmental DNA metabarcoding analysis

Human noroviruses (HNVs) are one of the major causes of food poisoning and severe gastroenteritis. However, prevention and medical treatment of HNV disease is underdeveloped due to the lack of ecological understanding of the HNVs including their host organisms. We address the potential source animals of HNVs based on the environmental DNA metabarcoding analysis. By focusing on the HNV-epidemic area in Japan, we found several bird species of ducks, pochards, carrion crow, and swan showing significant cross-correlation with the HNV detection from cultured oysters. Humans and livestock mammals do not exhibit correlation with HNVs. These results suggest an avian-sourced, non-human- or sewage-mediated model of HNV infection. Unraveling the unknown host animals of pathogens like HNV facilitates artificial propagation of the pathogen, leading to vaccine and small molecule drug development.

Fitness benefits of alternated chick provisioning in cooperatively breeding carrion crows.

In most bird species, parents raise offspring cooperatively. In some cases, this cooperation extends to helpers-at-the-nest who assist the breeders with a range of tasks. While cooperative food provisioning might merely arise incidentally, as a result of the efforts of carers that act independently from each other, recent studies suggest that birds may coordinate by taking turns in visiting the nest. However, evidence that such coordination emerges because individuals actively respond to each other's behaviour is controversial, and the potential benefits of carers' alternation remain unknown. We addressed this knowledge gap by analysing a multiyear dataset for cooperatively breeding carrion crows Corvus corone, comprising 8693 nest visits across 50 groups. Our results reveal that turn-taking does occur in this species and that all group members, regardless of their sex and social role (breeder/helper), tend to alternate at the nest with other carers rather than to make repeat visits. Importantly, we found that the body mass of nestlings increased significantly with the degree of carers' alternation, possibly because well-coordinated groups provided food at more regular intervals. Using earlier monitoring data, the observed increase in body mass is predicted to substantially boost postfledging survival rates. Our analyses demonstrate that alternation in nestling provisioning has measurable fitness benefits in this study system. This raises the possibility that cooperatively breeding carrion crows, as well as other bird species with similarly coordinated brood provisioning, exhibit specialized behavioural strategies that enable effective alternation.

Testing the effects of kinship, reciprocity and dominance on prosocial food provisioning in azure‐winged magpies (Cyanopica cyana), carrion crows (Corvus corone) and common ravens (C. corax)

AbstractProsocial behaviour (i.e. benefitting others without receiving a direct gain) has long been perceived as an evolutionary puzzle but is nevertheless relatively common among non‐human animals. Prosocial food provisioning has recently been documented in several large‐brained bird species, such as corvids and parrots. Yet, to date, little is known about which factors influence food provisioning in these species. Here, we investigated whether kinship, reciprocity and dominance affected food provisioning in the group service paradigm in three corvid species, namely azure‐winged magpies (Cyanopica cyana), carrion crows (Corvus corone) and common ravens (C. corax). In this paradigm, the subjects are tested in their regular social groups and can choose to make food available to their group members by landing on a simple seesaw apparatus. We found no evidence for an effect of kinship or reciprocity on food provisioning. Contrary to our predictions, the subjects' dominance was not positively correlated with their rate of food provisioning in any species. Among ravens, dominance was instead positively correlated with receiving food. We conclude that preferential provisioning for kin and direct reciprocity might have been impeded by the provider's inability to control who receives the food in the group service paradigm, but that our findings provide another piece of evidence that dominance is a highly important factor in the social interactions of common ravens.

Numerical Representation for Action in Crows Obeys the Weber-Fechner Law

The psychophysical laws governing the judgment of perceived numbers of objects or events, called the number sense, have been studied in detail. However, the behavioral principles of equally important numerical representations for action are largely unexplored in both humans and animals. We trained two male carrion crows (Corvus corone) to judge numerical values of instruction stimuli from one to five and to flexibly perform a matching number of pecks. Our quantitative analysis of the crows’ number production performance shows the same behavioral regularities that have previously been demonstrated for the judgment of sensory numerosity, such as the numerical distance effect, the numerical magnitude effect, and the logarithmical compression of the number line. The presence of these psychophysical phenomena in crows producing number of pecks suggests a unified sensorimotor number representation system underlying the judgment of the number of external stimuli and internally generated actions.

Chromatin accessibility, not 5mC methylation covaries with partial dosage compensation in crows.

The evolution of genetic sex determination is often accompanied by degradation of the sex-limited chromosome. Male heterogametic systems have evolved convergent, epigenetic mechanisms restoring the resulting imbalance in gene dosage between diploid autosomes (AA) and the hemizygous sex chromosome (X). Female heterogametic systems (AAf Zf, AAm ZZm) tend to only show partial dosage compensation (0.5 < Zf:AAf < 1) and dosage balance (0.5<Zf:ZZm<1). The underlying mechanism remains largely elusive. Here, we quantified gene expression for a total of 15 male and female Eurasian crows (Corvus (corone) spp.) raised under common garden conditions. In addition, we characterized aspects of the regulatory epigenetic landscape quantifying chromatin accessibility (ATAC-seq) and 5mC methylation profiles. Partial dosage balance and compensation was due to female upregulation of Z-linked genes which covaried significantly with increased chromatin accessibility of the female Z chromosome. 5mC methylation was tissue and sex chromosome-specific, but unrelated to dosage. With the exception of the pseudo-autosomal region (PAR), female upregulation of gene expression was evenly spread across the Z chromosome without evidence for regional centers of epigenetic regulation, as has, for example, been suggested for the male hypermethylated region (MHM) in chicken. Our results suggest that partial dosage balance and compensation in female heterogametic systems are tightly linked to chromosome-wide, epigenetic control of the female Z chromosome mediated by differential chromatin accessibility.

West Nile Virus Lineage 2 in Free-Living Corvus cornix Birds in Poland.

The summer temperatures recorded in Poland in 2022 were among the highest in over 30 years and, combined with higher-than-expected rainfall, gave the impression of an almost tropical climate. Such climatic conditions were ideal for the transmission of vector-borne zoonotic diseases such as West Nile fever. In northeastern Poland, in the Mazowieckie region, the Polish event-based surveillance network reported increased fatalities of free-living hooded crows (Corvus corone cornix). West Nile virus (WNV) lineage 2 was identified for the first time as the etiological agent responsible for the death of the birds. WNV was detected in 17 out of the 99 (17.17%) free-living birds tested in this study. All the WNV-infected dead birds were collected in the same area and were diagnosed in September by the NVRI and confirmed by the EURL for equine diseases, ANSES, in October 2022. Unnaturally high temperatures recorded in Poland in 2022 likely favored the infection and spread of the virus in the avian population. A nationwide alert and awareness raising of blood transfusion centers and hospitals was carried out to prevent human infections by WNV.

Zoonotic potential and antimicrobial resistance of Escherichia spp. in urban crows in Japan-first detection of E. marmotae and E. ruysiae

Little is known about the prevalence of antimicrobial-resistant bacteria and pathogenic Escherichia coli in crows (carrion and jungle crows). We studied the phylogeny, virulence and antimicrobial resistance gene profiles of crow E. coli isolates to investigate their zoonotic potential and molecular epidemiology. During the winter of 2021–2022, 34 putative E. coli isolates were recovered from 27 of the 65 fresh fecal samples collected in urban areas. Three strains of the B1-O88:H8-ST446-fimH54 lineage, classified as extraintestinal pathogenic E. coli (ExPEC) and necrotoxigenic E. coli type 2, were colistin-resistant and harbored mcr-1.1-carrying IncI2 plasmids. The blaCTX-M-55 was identified in a multidrug-resistant B1-O non-typeable:H23-ST224-fimH39 strain. In phylogroup B2, two lineages of O6:H1-ST73-fimH30 and O6:H5-ST83-fimH21 were classified as ExPEC, uropathogenic E. coli, and necrotoxigenic E. coli type 1 (O6:H5-ST83-fimH21), and contained several virulence genes associated with avian pathogenic E. coli. Noteworthy is that three isolates, identified as E. coli by MALDI-TOF MS, were confirmed to be two Escherichia marmotae (cryptic clade V) and one Escherichia ruysiae (cryptic clade III) based on ANI and dDDH analyses. Our results provide the first evidence of these new species in crows. E. marmotae and E. ruysiae isolates in this study were classified as ExPEC and contained the enteroaggregative E. coli heat-stable toxin 1 gene. In addition, these two E. marmotae isolates displayed a close genetic relationship with human isolates associated with septicemia. This study provides the first insights into the prevalence and zoonotic significance of Escherichia spp. in urban crows in Japan, posing a significant risk for their transmission to humans.

Effect of implementation of irrigation on raptor and corvid populations in a Mediterranean agrosystem

We analyzed changes in the composition of the community of birds of prey and corvids in a rainfed agrosystem after the transformation of 37.2 % of the sampled area into irrigated land between 2005 and 2020. We sampled 57 transects (372 km per year) and fitted generalized linear mixed models (GLMM) to study changes in species occurrence. Our results showed that specific richness and the Shannon index did not vary significantly between rainfed and irrigated transects, but there was a certain positive trend when comparing the years 2005 and 2020. Regarding the differences detected for each species, the occurrence of Montagu’s harrier Circus pygargus, hen harrier Circus cyaneus, Eurasian short-toed eagle Circaetus gallicus, griffon vulture Gyps fulvus and carrion crow Corvus corone was significantly lower in irrigated land than in rainfed land, while magpie Pica pica, Western marsh harrier Circus aeruginosus, common kestrel Falco tinnunculus and black kite Milvus migrans showed a significantly higher occurrence in the irrigated transects. In addition, our findings confirm a significant decrease in occurrence between 2005 and 2020 both in rainfed and irrigated areas for Montagu’s harrier, hen harrier and magpie, while Western marsh harrier, golden eagle Aquila chrysaetos, common buzzard Buteo buteo, red kite Milvus milvus, griffon vulture Gyps fulvus, red-billed chough Pyrrhocorax pyrrhocorax and Western jackdaw Coloeus monedula were detected significantly more frequently in 2020 than in 2005. These results suggest that assessment of the impact of a new irrigation system should focus on the most characteristic species of rainfed agrosystems because the apparently positive effect on other species, equally protected but more generalist, may mask the real effect on conservation.

Cognition: Crows are natural statisticians

A new study shows that carrion crows use memorized reward associations in a combinatorial way to apply relative probabilistic information to optimize reward outcome. This for the first time shows that a corvid species can flexibly apply statistical inference during decision making.

Costs and benefits of voluntary attention in crows.

Behavioural signatures of voluntary, endogenous selective attention have been found in both mammals and birds, but the relationship between performance benefits at attended and costs at unattended locations remains unclear. We trained two carrion crows (Corvus corone) on a Posner-like spatial cueing task with dissociated cue and target locations, using both highly predictive and neutral central cues to compare reaction time (RT) and detection accuracy for validly, invalidly and neutrally cued targets. We found robust RT effects of predictive cueing at varying stimulus-onset asynchronies (SOA) that resulted from both advantages at cued locations and costs at un-cued locations. Both crows showed cueing effects around 15-25 ms with an early onset at 100 ms SOA, comparable to macaques. Our results provide a direct assessment of costs and benefits of voluntary attention in a bird species. They show that crows are able to guide spatial attention using associative cues, and that the processing advantage at attended locations impairs performance at unattended locations.

Effects of meteorological conditions on brood care in cooperatively breeding carrion crow and consequences on reproductive success

Meteorological stressors (e.g., temperature and rain shortage) constrain brood provisioning in some bird species, but the consequences on reproductive success have been rarely quantified. Here we show, in a cooperatively breeding population of carrion crow Corvus corone in Spain, that individual feeding rates decreased significantly with rising air temperatures both in breeders and helpers, while lack of rain was associated with a significant reduction in the effort of the male helpers as compared to the other social categories. Group coordination, measured as the degree of alternation of nest visits by carers, was also negatively affected by rising temperature. Furthermore, we found that the body condition of the nestlings worsened when temperatures were high during the rearing period. Interestingly, the analysis of a long-term data set on crow reproduction showed that nestling body condition steadily deteriorated over the last 26-years. Although many factors may concur in causing population changes, our data suggest a possible causal link between global warming, brood caring behaviour and the decline of carrion crow population in the Mediterranean climatic region of Spain.

Are you better than me? Social comparisons in carrion crows (Corvus corone).

Comparing oneself to others is a key process in humans that allows individuals to gauge their performances and abilities and thus develop and calibrate their self-image. Little is known about its evolutionary foundations. A key feature of social comparison is the sensitivity to other individuals' performance. Recent studies on primates produced equivocal results, leading us to distinguish between a 'strong' variant of the social comparison hypothesis formulated for humans and a 'weak' variant found in non-human primates that would comprise some elements of human social comparison. Here, we focus on corvids that are distantly related to primates and renowned for their socio-cognitive skills. We were interested in whether crows' task performances were influenced (i) by the presence of a conspecific co-actor performing the same discrimination task and (ii) by the simulated acoustic cues of a putative co-actor performing better or worse than themselves. Crows reached a learning criterion quicker when tested simultaneously as compared to when tested alone, indicating a facilitating effect of social context. The performance of a putative co-actor influenced their performance: crows were better at discriminating familiar images when their co-actor was better than they were. Standard extremity (how pronounced the difference was between the performance of the subject and that of the co-actor), and category membership (affiliation status and sex), of the putative co-actors had no effect on their performance. Our findings are in line with the 'weak' variant of social comparison and indicate that elements of human social comparison can be found outside of primates.

Categorical representation of abstract spatial magnitudes in the executive telencephalon of crows

The ability to group abstract continuous magnitudes into meaningful categories is cognitively demanding but key to intelligent behavior. To explore its neuronal mechanisms, we trained carrion crows to categorize lines of variable lengths into arbitrary "short" and "long" categories. Single-neuron activity in the nidopallium caudolaterale (NCL) of behaving crows reflected the learned length categories of visual stimuli. The length categories could be reliably decoded from neuronal population activity to predict the crows' conceptual decisions. NCL activity changed with learning when a crow was retrained with the same stimuli assigned to more categories with new boundaries ("short", "medium," and "long"). Categorical neuronal representations emerged dynamically so that sensory length information at the beginning of the trial was transformed into behaviorally relevant categorical representations shortly before the crows' decision making. Our data show malleable categorization capabilities for abstract spatial magnitudes mediated by the flexible networks of the crow NCL.

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

The White-Tailed Sea Eagle (Haliaeetus albicilla) is a large bird of prey native to the Southern shore of Lake Balkhash. In 2021, a pair of White-Tailed Sea Eagles nested in a dry Poplar tree (Populus diversifolia) located 7.5–8 km southwest-south of the village of Karaoi, Balkash district, Almaty oblast, and raised two nestlings. The breeding territory was located in a transitional biome containing characteristics of wetlands closer to the Ile River delta and typical desert biotopes of the Southern Lake Balkhash. The nest was located in a cluster of poplar trees, only a few of which had relatively high height and trunk capacity, and only one of which was suitable for a large nest. The nest was annually rebuilt and successfully used for brooding by eagles for over 10 reproductive seasons. The breeding territory is located on “Duman-Ai” farm. There are no other poplar trees suitable for nesting within a 10 km radius of the nest. As a result of strong storm winds on July 8–9, 2021, the nest fell, together with the dry tree it was built on. However, by the end of June 2021, both fledglings had successfully fledged. In the spring of 2022, the nest and fallen poplar burned after several small fires were set in this location. Reed fires (often very extensive) and riparian fires (trees of various species of willow, Elaeagnus, and populus) along streams are common in the area, especially in early spring. As a result, riparian thickets have been in a severely depressed state for many decades, and in some places they are practically reduced to nothing, especially in the middle part of the Ile River delta. In the fall of 2021, with the assistance of the WWF Central Asia Program and cooperation with the Ile-Balkash State Nature Reserve, one of the authors of this publication constructed an artificial nest near the fallen tree using five vertically-placed logs and multiple cross-bars. A platform made of fallen dry branches and dead poplar twigs was installed in its upper part, imitating a similar nest structure. The height of the nesting platform itself was 5.5–5.8 m, which is no lower than the height of the original nest of this pair which fell. In 2022–2023, 12 birdhouses for small passerines were installed on the logs and cross-bars forming the structure. After the the structure was finished, monitoring of its use by different vertebrate species has been carried out almost monthly together with members of the ecological club consisting mainly of students from the Ulgili secondary school in Karaoy village. Monitoring of the artificial nest was also supported by the WWF Central Asia Program. The creation of such an artificial nest to attract a breeding pair of White-Tailed Sea Eagles was the first such endeavor in Kazakhstan, at least in the Southern shore of Lake Balkhash area. During 2021–2023, a pair of White-Tailed Sea Eagles from this breeding territory started to use it as a perch. In 2022–2023 Saxaul Sparrows (Passer ammodendri) nested repeatedly in the birdhouses installed in the structure, as well as in the branches of the artificial nest. Saxaul sparrows and Bukhara tit (Parus bokharensis) used the birdhouses for overnight stays in fall-winter and early spring. Afterwards, only Saxaul sparrows nested and hatched chicks in this site, including the 2023 season, having displaced the Bukhara tits. In neither 2022 nor 2023 did White-Tailed Sea Eagles nest on the platform. In September and October of 2022, the structure was frequently used by both individuals of the eagle pair for sleeping and resting, sometimes staying on it for many hours at a time. In late summer and fall of 2022, young eagle fledglings from this year were observed at this location, although it cannot be definitively stated that they were from this pair. In late January 2023, a pair was observed attempting to mate on the platform. The location of the platform within 150-200 m of a country road is clearly not conducive to nesting due to disturbance. The existing road is occasionally used by local fishermen, hunters, and small groups of people during the reed cutting season. Occasionally, vehicles attracted by this locally unusual object drove up to the nest (more often in 2021–2022 than in 2023), thus disturbing White-Tailed Sea Eagles sitting on the structure. Gunshots are heard in the area almost year-round. In the winter of 2022–2023, pieces of a cow carcass killed by wolves (Canis lupus) were placed on the nesting platform for the eagles. However, most of this meat was eventually consumed by Eastern Black Crows (Corvus corone orientalis) and Magpies (Pica pica). In late July – August 2023, the platform was used for resting and overnighting by adult White-Tailed Sea Eagles. Fledglings of this species were repeatedly observed at this location during the same period. It is possible that the local pair may have nested in a reed bed in the nearby lakes and channels of the wetland, the eastern boundary of which is located 400–500 m west of the nesting platform. Cases of eagle nesting on reed beds in this river delta have been described previously (Zhatkanbaev, 2011). Over the course of obsservations in late August and early September of 2023, no signs of nest construction were recorded, which could sometimes be observed in the fall in a number of birds of prey, including White-Tailed Sea Eagles. Measurements of another old massive nest of White-Tailed Sea Eagles on the left bank of the Naryn channel (Ile River delta), 12–13 km west-southwest of Karaoy village, which had fallen under its own weight, could be of interest. Another pair of White-Tailed Sea Eagles hatched nestlings there every year for at least 15–17 years. In 2022, one fledgeling successfully fledged from this nest. The nest and the live poplar tree on which it was built (trunk diameter at the base 35–38 cm, height to the lowermost branches of the crown 15.5–17.5 m) was found collapsed in March 2023, although in December 2022 it was still standing. It was clear that the primary reason for the fall was the extremely large mass of the nest, accumulated over many years of its constant renewal. Its weight, measured on August 25, 2023, in 23 separate parts using portable scales (accuracy to 0.05 kg) was 238.2 kg. The nest was 1.6–1.8 m in major diameter after the fall (excluding protruding branches and limbs), with the tamped-down mass of nesting material from previous years being at least 1.5–1.75 m high. The percentage of large branches was around 28–30%, some of them were 70–80 cm long, weighing up to 1.5–1.85 kg. Medium and especially small twigs, including those from the Saxaul and Indian Sparrow (Passer indicus) nests, made up the remaining 70–72% of the total nest mass. When the nest mass was dismantled, an unfertilized egg was found in the middle part of the nest, apparently covered over by the eagles many years ago during subsequent nest renewals.