Larus Ridibundus Research Articles

Antibiotic-resistant Escherichia coli from treated municipal wastewaters and Black-headed Gull nestlings on the recipient river

Wastewaters belong among the most important sources of environmental pollution, including antibiotic-resistant bacteria. The aim of the study was to evaluate treated wastewaters as a possible transmission pathway for bacterial colonisation of gulls occupying the receiving river. A collection of antibiotic-resistant Escherichia coli originating both from treated municipal wastewaters discharged to the river Svratka (Czech Republic) and nestlings of Black-headed Gull (Chroicocephalus ridibundus) living 35 km downstream of the outlet was obtained using selective cultivation. Isolates were further characterised by various phenotyping and genotyping methods.From a total of 670 E. coli isolates (450 from effluents, 220 from gulls), 86 isolates (41 from effluents, 45 from gulls) showed identical antibiotic resistance phenotype and genotype and were further analysed for clonal relatedness using pulsed-field gel electrophoresis (PFGE). Despite the overall high diversity of the isolates, 21 isolates from both sources showed similar PFGE profiles. Isolates belonging to epidemiologically important sequence types (ST131, 15 isolates; ST23, three isolates) were subjected to whole-genome sequencing. Subsequent phylogenetic analysis did not reveal any close clonal relationship between the isolates from the effluents and gulls' nestlings with the closest strains showing 90 SNPs difference.Although our study did not provide direct evidence of transmission of antibiotic-resistant E. coli to wild gulls via treated wastewaters, we observed gull chicks as carriers of diverse multi-resistant E. coli, including high-risk clones, posing risk of further bacterial contamination of the surrounding environment.

Effects of maternal androgens and their metabolite etiocholanolone on prenatal development in birds.

Offspring phenotypes can be affected by maternal testosterone and androstenedione (A4), which are considered a tool of mothers to adjust offspring to a fluctuating environment. Yet testosterone and A4 are very rapidly metabolized by developing avian embryos, suggesting that either the maternal testosterone and A4 have potent organizational effects on the embryos extremely early before being metabolized or it is the metabolites that evoke phenotypic variation in the offspring. One of the metabolites, etiocholanolone, increases substantially during early embryonic development and is a likely candidate for mediating maternal effects as it can promote erythropoiesis. To investigate and compare the effects of testosterone and A4 with the possible effects of etiocholanolone during prenatal embryonic development, we increased their levels in black-headed gull eggs (Larus ridibundus), and used sham-injected eggs as controls. This species usually has 3-egg clutches in which maternal androgen levels increase with the egg-laying sequence. We analysed embryonic heart rate, peri-hatching biometric traits, the ratio of white to red blood cells (W/R ratio) and bursa development. We found that testosterone and A4 treatment increased embryonic heart rate irrespective of egg-laying sequence and decreased bill length and W/R ratio, whereas etiocholanolone did not mimic these effects. Instead, etiocholanolone treatment decreased tarsus length and brain mass. Our finding that etiocholanolone does not mimic the effects induced by testosterone and A4 suggests that the embryonic metabolism of maternal testosterone and A4 can potentially diversify the function of these maternal androgens.

The genome sequence of the black-headed gull, Chroicocephalus ridibundus (Linnaeus, 1766)

We present a genome assembly from an individual male Chroicocephalus ridibundus (the black-headed gull; Chordata; Aves; Charadriiformes; Laridae). The genome sequence spans 1,417.60 megabases. Most of the assembly is scaffolded into 33 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled and is 16.82 kilobases in length.

Helminths of the black-headed gull (Chroicocephalus ridibundus) from breeding colonies in north-central Poland

Among parasites of the digestive tract of the black-headed gull (Chroicocephalus ridibundus) in Poland, the best known are species of digenetic trematodes and cestodes. Nematodes of this bird species are not well known. Black-headed gulls, due to their varied diet, migration, life in a flock, and changes of habitat, can become infected with various species of helminths, and like synanthropic birds, they can spread the dispersal stages of parasites across urban and recreational areas. In the present study, an attempt was made to identify the helminth fauna of C. ridibundus from breeding colonies in north-central Poland. The aim of the study was to describe the taxonomic structure of parasites of the digestive tract of the black-headed gull and determine the quantitative parameters of their occurrence. A total of 43 black-headed gulls were examined post-mortem for gastrointestinal helminths, resulting in the identification of four cestodes (Paricterotaenia porosa, Lateriporus clerci, Anomotaenia micracantha, and Wardium fusum), three trematodes (Diplostomum pseudospathaceum, Plagiorchis laricola, and Apophallus muehlingi), and three nematodes (Eucoleus contortus, Cosmocephalus obvelatus, and Porrocaecum ensicaudatum). Lateriporus clerci (in adult form), C. obvelatus and P. ensicaudatum (in larval form) were recorded for the first time in the black-headed gull in Poland.

Age differences in primary moult of the Black-headed Gull Chroicocephalus ridibundus

Flight feather moult is an energetically expensive stage of the annual cycle of birds. Its timing is adjusted to other important time- and energy-demanding activities, including migration. In the vast majority of migratory birds, primary moult occurs before or after migration or moulting is suspended during migration. The Black-headed Gull is an exception: it starts moulting flight feathers at the onset of the autumn migration. The course of primary moult in this species is still poorly understood due to the difficulty in obtaining sufficient data from the entire period of flight feather replacement. In this paper, we employed digital photos taken in the field to estimate the start, variation in the start date and duration of primary moult in adult and immature Black-headed Gulls, by using the Underhill–Zucchini likelihood moult model. On average, immatures started their moult on 7 June, 25 days earlier than adults, but their moult lasted 5 days longer. Consequently, there was a 20-day difference in the end of moult – that is, on average it occurred on 16 September and 6 October in immature and adult gulls, respectively. Adults showed greater variability in the mean primary moult start date than immatures, as the beginning of flight feather replacement may depend on breeding success (earlier after breeding failure) and on breeding phenology. The overlap of primary moult and migration produces a trade-off in resource allocation between those two processes, which leads to a low number of simultaneously growing primaries and a decrease in the growth rate of the two external, heaviest flight feathers. Existing reports of a later completion of primary moult in the first half of November in this species are based on the faulty assumption that the outermost primary is always the longest, which is not the case in 34% of individuals.

Highly pathogenic avian influenza A(H5N1) virus infections on fur farms connected to mass mortalities of black-headed gulls, Finland, July to October 2023.

Highly pathogenic avian influenza (HPAI) has caused widespread mortality in both wild and domestic birds in Europe 2020-2023. In July 2023, HPAI A(H5N1) was detected on 27 fur farms in Finland. In total, infections in silver and blue foxes, American minks and raccoon dogs were confirmed by RT-PCR. The pathological findings in the animals include widespread inflammatory lesions in the lungs, brain and liver, indicating efficient systemic dissemination of the virus. Phylogenetic analysis of Finnish A(H5N1) strains from fur animals and wild birds has identified three clusters (Finland I-III), and molecular analyses revealed emergence of mutations known to facilitate viral adaptation to mammals in the PB2 and NA proteins. Findings of avian influenza in fur animals were spatially and temporally connected with mass mortalities in wild birds. The mechanisms of virus transmission within and between farms have not been conclusively identified, but several different routes relating to limited biosecurity on the farms are implicated. The outbreak was managed in close collaboration between animal and human health authorities to mitigate and monitor the impact for both animal and human health.

Genetic characterization of the first Deltacoronavirus from wild birds around Qinghai Lake.

Deltacoronavirus, widely distributed among pigs and wild birds, pose a significant risk of cross-species transmission, including potential human epidemics. Metagenomic analysis of bird samples from Qinghai Lake, China in 2021 reported the presence of Deltacoronavirus. A specific gene fragment of Deltacoronavirus was detected in fecal samples from wild birds at a positive rate of 5.94% (6/101). Next-generation sequencing (NGS) identified a novel Deltacoronavirus strain, which was closely related to isolates from the United Arab Emirates (2018), China (2022), and Poland (2023). Subsequently the strain was named A/black-headed gull/Qinghai/2021(BHG-QH-2021) upon confirmation of the Cytochrome b gene of black-headed gull in the sample. All available genome sequences of avian Deltacoronavirus, including the newly identified BHG-QH-2021 and 5 representative strains of porcine Deltacoronavirus (PDCoV), were classified according to ICTV criteria. In contrast to Coronavirus HKU15, which infects both mammals and birds and shows the possibility of cross-species transmission from bird to mammal host, our analysis revealed that BHG-QH-2021 is classified as Putative species 4. Putative species 4 has been reported to infect 5 species of birds but not mammals, suggesting that cross-species transmission of Putative species 4 is more prevalent among birds. Recombination analysis traced BHG-QH-2021 origin to dut148cor1 and MW01_1o strains, with MW01_1o contributing the S gene. Surprisingly, SwissModle prediction showed that the optimal template for receptor-binding domain (RBD) of BHG-QH-2021 is derived from the human coronavirus 229E, a member of the Alphacoronavirus, rather than the anticipated RBD structure of PDCoV of Deltacoronavirus. Further molecular docking analysis revealed that substituting the loop 1-2 segments of HCoV-229E significantly enhanced the binding capability of BHG-QH-2021 with human Aminopeptidase N (hAPN), surpassing its native receptor-binding domain (RBD). Most importantly, this finding was further confirmed by co-immunoprecipitation experiment that loop 1-2 segments of HCoV-229E enable BHG-QH-2021 RBD binding to hAPN, indicating that the loop 1-2 segment of the RBD in Putative species 4 is a probable key determinant for the virus ability to spill over into humans. Our results summarize the phylogenetic relationships among known Deltacoronavirus, reveal an independent putative avian Deltacoronavirus species with inter-continental and inter-species transmission potential, and underscore the importance of continuous surveillance of wildlife Deltacoronavirus.

Population size and nesting peculiarities of the black-headed gull Chroicocephalus ridibundus (Linnaeus, 1766) on the territory of water treatment facilities

Background. Today, the black-headed gull inhabits man-made areas of wastewater treatment facilities (WTF) to comensate for the the reduction of natural aquatic and wetland habitats. Over the last decade, a nearly tenfold increase in its population has been recorded, despite a low reproduction rate. This fact indicates the lack of stability in the bird population, necessitating thorough research. Materials and Methods. The analysis of the population size and biological charac­teristics of black-headed gulls involved censuses and observations at the WTF of the city of Kharkiv using conventional methods during the spring-summer periods of 2020–2021 and 2023. Results. The population of the black-headed gull reached its peak in the third decade of May 2020 (2637 individuals) and 2023 (2124 individuals), as well as in the second decade of May 2021 (3949 individuals). The maximum nesting density was observed on sludge sites (SS) of wastewater treatment facilities that are most similar to natural habitats, where dried mud alternates with water patches and vegetation at the bottom and around the perimeter (Type V): 236.7±26.7 pairs/ha in 2020 and 242.9±28.5 pairs/ha in 2021. The majority of nests were found in the first decade of May 2021 and the third decade of May 2020. The black-headed gull forms mixed-species, occasionally monospecific subcolonies. Nesting in association with it were: Sterna hirundo, Anas platyrhynchos, Spatula clypeata, Vanellus vanellus, Charadrius dubius, Himantopus himantopus, Fulica atra, Gallinula chloropus, and Aythya ferina. The size of the complete black-headed gull clutch was 3.1±0.4 eggs (n = 190). The egg dimensions were 50.9±2.1 ´ 36.2±1.1, with a mass of 34.6±2.8 g. Regarding shell coloration, five types of background colors were identified. Mass egg laying occurred from the third decade of April to the first decade of May, constituting 40.3 % (n = 993) in 2020 and 62.3 % (n = 1757) in 2021. The egg-laying period extended from April to July, with the latest non-incubated clutches recorded in the first decade of July (3.07.2020). The first chicks were found in nests in the first decade of May, while mass hatching occurred in the second half of May. The latest registration dates of the birds on nesting territories were in the second decade of July for 2020 and 2023, and the first decade of August for 2022. The nesting season duration varied from 125 to 140 days in different years. Autumn migration commenced with summer relocations and concluded from late October to early November. The reproductive success – the percentage of nestlings that fledged and successfully achieved flight – constituted 29.2 % (n = 2404 of laid eggs) in 2020, and 15.5 % (n = 6138) in 2021. The majority of offspring perished due to changes in water levels (prolonged rainfall or industrial wastewater discharge), predation, disturbance factors, etc. Conclusion. The colonial nesting of the black-headed gull creates favorable conditions for the habitation and reproduction of various bird species, including rare ones, which is essential for their conservation.

Second Prebasic Molt of a Black-headed Gull at Anchorage, Alaska

A second-cycle Black-headed Gull (Chroicocephalus ridibundus), a rare to casual visitor in western North America, remained at Anchorage, Alaska, from 16 July through 17 September 2023, providing a unique opportunity to track and document most stages of its second prebasic molt into definitive (adult) basic plumage. I estimated that the Anchorage bird required approximately 3 to 3.5 months (early/mid-June through late September) to complete the molt of its primaries. This is notably longer than the “average” 2.5 months stated for second-cycle Black-headed Gulls in several publications, but consistent with the duration and calendar limits reported by others for the entire species (mid-May/June through September). The start and duration of rectrix molt relative to the stage of primary molt closely matched that described for gulls in general, and specifically for predefinitive Bonaparte’s (C. philadephia) and Western (Larus occidentalis) gulls. When first observed in mid-July, the Anchorage bird had a white tail, as in definitive plumage, a trait infrequent in first-cycle Black-headed Gulls; then it molted the tail again through August. Although Black-headed Gulls occurring in western North America have been presumed to originate from eastern Asia, the timing of the Anchorage bird’s primary molt closely matched that published for second-cycle Black-headed Gulls in Europe, which has reported to be earlier—though molt schedules of Charadriiformes at the population level are highly variable.

Mercury stable isotopes in seabirds in the Ebro Delta (NE Iberian Peninsula): Inter-specific and temporal differences

Mercury (Hg) is a global pollutant, which particularly affects aquatic ecosystems, both marine and freshwater. Top-predators depending on these environments, such as seabirds, are regarded as suitable bioindicators of Hg pollution. In the Ebro Delta (NE Iberian Peninsula), legacy Hg pollution from a chlor-alkali industry operating in Flix and located ca. 100 km upstream of the Ebro River mouth has been impacting the delta environment and the neighboring coastal area. Furthermore, levels of Hg in the biota of the Mediterranean Sea are known to be high compared to other marine areas. In this work we used a Hg stable isotopes approach in feathers to understand the processes leading to different Hg concentrations in three Laridae species breeding in sympatry in the area (Audouin's gull Ichthyaetus audouinii, black-headed gull Chroicocephalus ridibundus, common tern Sterna hirundo). These species have distinct trophic ecologies, exhibiting a differential use of marine resources and freshwater resources (i.e., rice paddies prey). Moreover, for Audouin's gull, in which in the Ebro Delta colony temporal differences in Hg levels were documented previously, we used Hg stable isotopes to understand the impact of anthropogenic activities on Hg levels in the colony over time. Hg stable isotopes differentiated the three Laridae species according to their trophic ecologies. Furthermore, for Audouin's gull we observed temporal variations in Hg isotopic signatures possibly owing to anthropogenic-derived pollution in the Ebro Delta. To the best of our knowledge this is the first time Hg stable isotopes have been reported in seabirds from the NW Mediterranean.

A case of polymelia in the Black-headed Gull Chroicocephalus ridibundus

Polymelia is a malformation consisting of the presence of supernumerary limbs. Although relatively common in farm animals and anurans, it is quite rare in wild vertebrates and, especially, birds. I describe here the case of a Black-headed Gull Chroicocephalus ridibundus seen in Barcelona (Catalonia, NE Spain) in January and February 2023 that had an atrophic leg originating from the distal posteromedial part of its right tibiotarsus. It was a healthy-looking bird, apparently in its second winter, and showed normal behaviour with no visible signs of any other pathology or malfunction. We are only aware of one previous case of polymelia in gulls and this is the first time it has been reported in a Black-headed Gull. It is also good example of survival in a bird affected by polymelia.

High pathogenicity avian influenza A (H5N1) clade 2.3.4.4b virus infection in a captive Tibetan black bear (Ursus thibetanus): investigations based on paraffin-embedded tissues, France, 2022.

Avian influenza viruses are able to cross the species barrier between birds and mammals because of their high genetic diversity and mutation rate. Using formalin-fixed paraffin-embedded tissues, we were able to investigate a Tibetan black bear's infection by a high pathogenicity H5N1 avian influenza virus at the molecular, phylogenetic, and histological levels. Our results highlight the importance of virological surveillance programs in mammals and the importance of raising awareness among veterinarians and zookeepers of the clinical presentations associated with H5Nx virus infection in mammals.

Parasites as Indicators of Biotic Interrelations between Fishes and Waterbirds

The paper deals with the structural features of the waterbirds' cenoses, the fish population composition and distribution of metacercariae of trematodes, whose final hosts are waterbirds, in the model shallow lentic ecosystems of the city of Kyiv (Almazne, Martyshev, Verbne lakes and Sovski ponds). The waterbird cenosis was dominated by ichthyophagous (58.5-75.7%) and pantophagous birds (16.4-41.42%). The black-headed gull <i>Chroicocephalus ridibundus</i> (21.9-56.7%) prevailed in terms of relative abundance everywhere. The ornithocenoses differed in terms of the subdominant species: in the Almazne lake it was <i>Podiceps cristatus</i>, in the Martyshev Lake - <i>Sterna hirundo </i>(14.6%), in the Sovski ponds and Verbne Lake - <i>Anas platyrhynchos</i> (12.8-20.2%). Differences in the coastal ornithocenoses' composition were confirmed by results of the cluster analysis WPGMA (weighted pair-group centroid (median)); distance measure - 1-Pearson <i>r</i>). The coastal fish population comprised 24 species, including the native fresh-water (15 species), Ponto-Caspian and Mediterranean self-dispersers (4 species), and alien species - distant invaders (5 species). Parasitological studies revealed trematode metacercariae localized in lens (<i>Diplostomum</i> sp.) and vitreous body (<i>Tylodelphys clavata</i>) of the eye, ripples (<i>Apatemon gracilis</i>), and in the integument of the body (<i>Posthodiplostomum cuticola</i>). The discriminant analysis enabled to reveal significant differences in the species composition and abundance of trematode metacercariae in the water bodies with different structure of the water ornithocenoses (Wilks' Lambda: approx. 0.92235; <i>F</i>(8, 510) = 2.6293f) - 2.6293; the dispersion analysis showed confidently lower total number of trematode metacercariae in the Almazne Lake (Wilks' Lambda = 0.87377; <i>F</i>(6, 432) = 5.0253; <i>p</i><0.00005).

Severe decline in abundance of Cyathostoma lari, a parasite of the nasal and orbital sinuses of gulls, at their central European nesting grounds.

Cyathostoma lari is a parasite of the nasal and orbital sinuses of gulls and other hosts in Europe and Canada. Here, we provide an overview of previously published data on the prevalence and infection intensity of C. lari in gulls. Furthermore, based on our data, we analyze the spatiotemporal trends in the prevalence and intensity of infection by C. lari in Chroicocephalus ridibundus in Czechia (central Europe; data from 1964 to 2014) and compare them with those obtained from five species of gulls in Karelia (Northwest Russia; data from 2012-2020). Based on our preliminary observations, we hypothesized that C. lari is subject to a decline in certain regions, but this decline is not necessarily applicable throughout its distribution range. We found that the C. lari population crashed in specific parts of its distribution range. The reasons are unknown, but the observed population changes correspond with the diet switch of their core host in Czechia, C. ridibundus. We previously observed a diet switch in Czech C. ridibundus from earthworms (intermediate hosts of C. lari) to other types of food. This diet switch affected both young and adult birds. Nevertheless, it may not necessarily affect populations in other regions, where they depend less on earthworms collected from agrocenoses affected by agrochemicals and trampling. Correspondingly, we found that these changes were limited only to regions where the gulls feed (or fed) on arable fields. In Karelia, where arable fields are scarce, gulls likely continue to feed on earthworms and still display high infection rates by C. lari. Therefore, C. lari, a parasite of the nasal and orbital sinuses of gulls, nearly disappeared from their central European nesting grounds but is still present in better-preserved parts of its distribution range.

PATHOMORPHOLOGICAL CHANGES IN THE KIDNEYS OF THE BLACK-HEADED GULL WITH URURIC DIATESIS

The article provides data on pathomorphological changes in the kidneys of the black-headed gull (Larus Ridibundus L., 1766) with uric acid diathesis. The material (kidney pieces) was collected from clinically healthy birds removed from their natural habitat using the generally accepted method. Macroscopic and histological studies were carried out in the dissecting room and laboratory of the Department of Pathological Anatomy and Histology of the Vitebsk State Academy of Veterinary Medicine. Preparation of histological sections and their staining were carried out according to generally accepted methods. With uric acid diathesis, the black-headed gull's kidneys were enlarged in size with diffusely located foci of urate deposition. Microscopic changes were characterized by the appearance of basophiliceosinophilic cylinders of crystalline and round-oval shape in the urine-forming tubules, collecting ducts and the lumen of the vascular glomeruli. The deposition of uric acid salts led to atrophy of the kidney structures, their necrosis and desquamation. In the parenchyma of the organ, proliferation of connective tissue with the formation of interstitial nephritis was detected.

To the fauna of rare bird species of coastal habitats of Temryuk Bay

New information on the presence of 27 rare, protected or little-studied species and subspecies of birds (greylag and red-breasted geese, common shelduck, gadwall, common pochard, Eurasian oystercatcher, pied avocet, black-winged stilt, Eurasian golden-plover, Eurasian curlew, sanderling, common greenshank, yellow-legged, great black-headed, Mediterranean, slender-billed, and little gulls, Caspian tern, European turtle-dove, great white and dalmatian pelicans, squacco heron, glossy ibis, Eurasian spoonbill, lesser spotted and white-tailed eagles, Eurasian hobby) obtained in the Temryuk region (Eastern Azov region) in different seasons of 2022-2023. The coast of the bay is a stopping place on the spring migration of Eurasian oystercatcher, pied avocet, Eurasian golden-plover, Eurasian curlew, sanderling, common greenshank, common shelduck, slender-billed gull, and Caspian tern; in the fall - pied avocet, sanderling, and Caspian tern. Information about the migration of the sanderling at the end of March has been obtained for the first time. The location of the concentration of Caspian tern and slender-billed gull has been identified. The glossy ibis, the number of which is growing, the black-winged stilt, and the great black-headed gull remain in the spring-summer period in the flooded rice fields. Harvested rice fields provide valuable habitat for Eurasian spoonbills during their fall migration. Information about a large aggregation of red-breasted goose in rice fields in January 2023 is presented for the first time. The great black-headed gull is found on estuaries in all seasons. The common pochard, gadwall, little gull, and Dalmatian pelican stop at the estuaries during the migration period. The migration of the lesser spotted eagle at the end of September and the migration of a large flock of great white pelican in May were recorded in this area for the first time. The squacco heron, which is disturbance tolerant, is common in reed habitats of estuaries and irrigation canals.

Water Bodies of Kazan and Their Significance in the City’s Avifauna Conservation

Water bodies that serve as habitats for semi-aquatic birds have been preserved in the city of Kazan, which contributes to the conservation of the city's avifauna diversity. Previously, special studies of birds in the water bodies of Kazan were not conducted. The study is aimed at the investigation of the species composition and distribution of the avifauna in water bodies of Kazan, as well as the ecological features of specific semiaquatic fauna species of the city. The research carried out over the past twenty-five years has made it possible to identify the species composition, their distribution, and ecological features of particular bird species associated with aquatic ecosystems. In total, 64 bird species of nine bird orders are recorded within the city of Kazan. The number of particular species and their spatial distribution in the city's water bodies depends on the specific conditions of the water object, where human activity is the major limiting factor. The most numerous species during the breeding period are the black-headed gull and the mallard. Nesting of 26 species has been recorded. A number of species, such as the mallard, show broad potential for synanthropization. The great-crested grebe, the coot and several species of ducks actively colonize the city reservoirs. A number of rare bird species listed in the Red Book of Tatarstan were recorded, including nesting of the mute swan, the moorhen.

Water bodies of former peat pits as the most important nesting sites for some species of Laridae in the center of European Russia

In this paper, we analyze the role of artificial water bodies in the former peat pits as habitats for gulls and terns based on long-term monitoring data in the Nizhny Novgorod oblast (area 76.624 km2), located in the center of European Russia. 3 regional censuses of Laridae were carried out in 1985-87, 1997, and 2006-2007. The monitoring of the largest colony of gulls in the region at the IBA Sitnikovski RU-185 was carried out in 1982, 1987, 1994, 1997, 2002, 2006, 2011 and 2023. It is shown that very large colonies of many species of Laridae, representing complexes of closely located colonies, have formed on the peat pits in the Nizhny Novgorod oblast. Peat pits are the most important nesting sites for Larus ridibundus, L. canus and L. argentatus in the central part of European Russia. In the Nizhny Novgorod oblast, more than 50% of the regional population of these species nests in these habitats. Monitoring only the Sitnikovski colony allows us to judge the trends in the numbers of most species of Laridae in the Nizhny Novgorod oblast at large. Based on extrapolation of population data at Sitniki peat pits we can calculate the approximate numbers of regional breeding populations of Larus minutus, L. ridibundus, L. canus and L. argentatus.

МОНИТОРИНГ ВОЗБУДИТЕЛЕЙ ОСНОВНЫХ ПАРАЗИТОЗОВ ВОДНЫХ ПТИЦ НА ИЗОЛИРОВАННОЙ ПРИРОДНОЙ ТЕРРИТОРИИ НАЦИОНАЛЬНОГО ПАРКА «ЛОСИНЫЙ ОСТРОВ»

An important point in the conservation of biological diversity and avifauna resources on the territory of national and zoological parks, reserves, as well as commercial breeding poultry enterprises is the study of the bioecology of parasitosis pathogens. In this study, for the first time in a long time, the results of bioecological monitoring of the main parasitoses of aquatic birds living in the isolated natural territory of NP "Losiny оstrov" are presented. The main focus of the work was the study of the spread of the invasive origin in intermediate, additional and final hosts, as well as the conservation potential of aquatic bird species and other components of the biogeocenosis. The article presents the results of helminthological studies of feces of birds of the gull families (lake gull Larus Ridibundus) and duck (mallard Anas Platyrhynchos); helminthological studies of the gastrointestinal tract of fish of the cyprinid family (bream Abramis Brama) and firebrand (perch Perca Fluviatilis); mollusks of the family Lymnaeidae and the family Planorbidae. 85 and 86 individuals of fish and shellfish, respectively, and 116 samples of bird droppings were studied. The number of identified samples from seagulls was 23, from ducks – 47, the remaining 46 samples were defined as «blind samples». The main composition of intestinal parasites of aquatic birds and aquatic organisms has been revealed. Data were obtained on the infection of aquatic birds with associative helminth-protozoal mixinvasion: genera – Eimeria and Trichomonas and helminths of genera: Capillaria, Amidostomum, Heterakis. At the same time, the presence of mixed invasion was noted in 64.28% of the total number of samples. Data were obtained on the infection of fish and shellfish, the helminth fauna of which is represented by the families Echinoctomatidae and Diplostomum sp. The extent of monoinvasion of mollusks of the species Lymnaea stagnalis by cercariae and metacercariae of trematodes of the family Echinoctomatidae was 62.16%.

Differences of water chemistry, bird assemblages and nutrient loads introduced by waterbirds into morphologically similar waterbodies

The number and structure of waterbirds is affected by the size of the waterbody, the presence of islands and macrophytes, but also by their trophy status. The aims of the study were to compare nutrients in water, numbers of waterbird assemblages, and the loading of nitrogen and phosphorus introduced by waterbirds in two similar waterbodies with different rates of water discharge. This study was conducted in two eutrophic shallow waterbodies, P1 and P2 in 2016 and 2017. The median concentrations of NO2 - , NO3 - and NH4 + were 4.0 times, 3.2 times, and 1.7 times greater in the P1 than in the P2 location, respectively. Similar proportions of organic matter in sediments were statistically greater in P1. The number of birds was also significantly greater in P1 than in P2. The waterbirds (Anas platyrhynchos, Aythya fuligula, Fulica atra, Phalacrocorax carbo and Chroicocephalus ridibundus) excreted 5.2 times more total phosphorous and 3.3 times more total nitrogen in P1 than in P2. Significant negative correlations were also found between the concentrations of NO3 - and the number of waterbirds in P1.