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The carcasses of ten great cormorants (Phalacrocorax carbo) found in one colony in the province of Vojvodina were necropsied and examined for parasites. The study aimed to identify helminths and histopathologically evaluate the associated tissue damage. Numerous nematodes were observed, either free in the the lumen of the ventriculus or deeply embedded in the ventricular mucosa of all the cormorants examined. The collected parasite samples were morphologically identified as Contracaecum rudolphii sensu lato. The main pathological findings included a thickening of the ventricular wall, while histopathology revealed a mild inflammatory infiltrate in the adjacent tissue and a connective tissue capsule around the parasite. Given that the parasites in this bird species still need to be thoroughly studied in our country, particularly the pathomorphological changes they cause, this study represents the first attempt to obtain a comprehensive understanding picture of the nematode infection and the pathological changes resulting from the presence of this parasite. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms have a strong impact on the food web structure, interactions and ecosystem functioning. The aim of this study was to describe the seasonal changes in composition and abundance of heterotrophic nanoflagellates, ciliates, rotifers, and crustaceans in relation to algae and nutrients in a shallow eutrophic lake (north-eastern Poland) dominated by cyanobacteria and exposed to the strong impact of cormorants. Our results showed that algae accounted for a small part of the total phytoplankton abundance (9–40%) and biomass (10–21%) and were dominated by diatoms and cryptophytes. All of the studied groups of planktonic organisms were quite rich in species (95 algal, 79 ciliate, 44 rotifer and 25 crustacean species) and relatively abundant. Copepods formed a substantial part (45–83%) of the total zooplankton biomass during all seasons. Relatively low algal to zooplankton biomass ratio (0.8–1.1) suggests that during spring, summer, and winter algae were not sufficient food resources for metazooplankton, which supplemented its diet with protists (heterotrophic nanoflagellates and ciliates). In a shallow lake dominated by cyanobacteria, winter (ice-covered period) may be a more favourable period for the growth of some groups of algae, ciliates and rotifers than other seasons due to decreasing abundance of cyanobacteria. [ABSTRACT FROM AUTHOR]

Concentrations of 4 potentially toxic elements (As, Cd, Hg, Pb) were investigated in the feather, liver, kidney, and bone of great cormorants (Phalacrocorax carbo). The tissue samples were taken at the Central Tisza - Jászság Nature Conservation Area in Hungary. They were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The goal of the investigation was to analyse the metal burden of the above-mentioned elements in the various tissues of these wild birds and to provide important information for monitoring the environmental pollution. Amongst the examined potentially toxic elements no statistical gender difference was observed, so the data were not separated based on them during the statistical analysis. The concentration of mercury was the highest in the feather, followed by the liver, kidney, and bone. The lead was detected in the feather with the highest level followed by the kidney, liver, and bone. The cadmium was determined in all investigated tissues with the next descending order: kidney > bone > liver > feather. Highest arsenic concentration was measured in the feather, followed by liver, kidney, and bone with the same concentration. The detected concentrations of the investigated potentially toxic elements in different tissues of great cormorants (feathers, liver, kidney, bone) means that the living area of this birds is not highly contaminated to induce health problems or toxic signs, or even other undesirable effect in the animals. [ABSTRACT FROM AUTHOR]

Juvenile salmonids often experience high mortality rates during migration and bird predation is a common source of mortality. Research suggests that hatchery‐reared salmonids are more prone to predation than wild salmonids, and that Atlantic salmon (Salmo salar) experience lower predation than Sea trout (Salmo trutta), yet telemetry studies have displayed equivocal results. Here, using a large data set on passive integrated transponder (PIT) tagged hatchery‐reared and wild juveniles of Atlantic salmon and Sea trout (25,769 individuals) we investigate predation probability by piscivorous birds (mainly Great Cormorants Phalarocorax carbo) on salmonids originating from River Dalälven in Sweden. Bird colonies and roosting sites were scanned annually (2019–2021), and the temporal dynamics of bird predation on salmonids released in 2017–2021 was assessed. Hatchery‐reared trout was clearly most susceptible to cormorant predation (0.31, 90% credibility interval [CRI] = 0.14–0.53), followed by wild trout (0.19, 90% CRI = 0.08–0.37), hatchery‐reared salmon (0.13, 90% CRI = 0.07–0.23), and wild salmon (0.08, 90% CRI = 0.04–0.14), in subsequent order. This order in predation probability was consistent across all studied tag‐ and release‐years, suggesting that the opportunistic foraging of cormorants affects the overall survival of juvenile salmonids, but that the inherent predation risk between different salmonid types differs systematically. [ABSTRACT FROM AUTHOR]

Some characteristics regarding the ecology of the waterbirds observed on the Vidraru Dam Basin between April 2022 and March, 2023 are shown in this paper. The constancy, the dominance, the Dzuba Index of ecological significance, the Index of Relation, the coenotic affinity, the diversity and the equitability of the species were discussed. Also, some remarks about the density of the species were done. 14 species of waterbirds were observed during the period of study and, generally, Anas platyrhynchos, Mergus merganser, Phalacrocorax carbo and Larus cachinnans were the most important among them in the ecosystem. As a result, Anseriformes, Suliformes and Charadriiformes were the overdominant orders of the avicoenose. The richness and the density of the species were low by comparison with the ones found on the dam basins from the downstream, proving that, currently, the Vidraru Dam Basin has a relatively low importance for the waterbirds, except for Mergus merganser, the only species certainly breeder here, and of other few species, which stay or pass through the area, the most in rather low numbers. [ABSTRACT FROM AUTHOR]

This study aimed to investigate how great cormorants and grey herons affect the density and trophic diversity of soil nematodes under breeding colonies located in Stawy Raszyńskie Nature Reserve (central Poland). Soil samples from the colonies were compared to control samples from adjacent areas unaffected by birds. Samples were taken at each site (two colonies and two relevant control sites) to a depth of 20 cm, and the soil cores were split into topsoil (0–10 cm) and subsoil (10–20 cm). A modified Baermann method was used to extract nematodes from the soil. The soil under nests supported more abundant nematode communities, but with a lower trophic diversity compared to the control sites. The cormorants had a greater impact on nematodes than the herons. We found that the external nitrogen input, the higher organic matter content and abundance of ammonifying bacteria, as well as the lower soil pH under the colonies than in the control sites, affected the nematode trophic groups in different ways. Compared to the control sites, there were significantly more bacterivorous nematodes but fewer herbivorous nematodes under the colonies. No predatory nematodes were found under the bird colonies and, in the case of the cormorant colony, no omnivorous nematodes. No significant differences in the abundance of fungivorous nematodes between the impact and the control plots were noticed. The results indicate that allochthonous input under bird colonies promotes microbial activity and the most opportunistic trophic group of nematodes, which may at least temporarily enhance decomposition and mineralisation processes and consequently affect nutrient cycling in the wetland soil.

During 2014–2019, the prevalence of Corynosoma spp., a parasite species in great cormorants (Phalacrocorax carbo spp.) and in Baltic herring (Clupea harengus membras), was studied in the Archipelago and the Bothnian Seas of the northern Baltic Sea. These results suggest that cormorants may act as a definitive host for these acanthocephalan parasites. Adults were more infected with the parasites than juveniles, which could be due to their larger size. A lower prevalence of Corynosoma spp. in juveniles may be because smaller cormorants eat smaller fish that have less parasites. We found that the most abundant corynosoma species in both the Baltic herring and cormorants were Corynosoma semerme, whereas only a few individuals of C. strumosum and only one C. magdaleni were found. The prevalence of corynosoma in herring increased from 2014 to 2018, and individuals in the Bothnian Sea were infected less frequently than herring in the Archipelago Sea. Results also showed that infected herring individuals were generally larger than non-infected individuals, which could be explained by their size and their feeding habits. Currently, the changing environment of the Baltic Sea may cause an effect on the herring making them more susceptible to infections. Our results, therefore, emphasize the importance of the regular monitoring of infections and the parasite-host relationships in the Baltic Sea.

Abstract Juvenile salmonids often experience high mortality rates during migration and bird predation is a common source of mortality. Research suggests that hatchery‐reared salmonids are more prone to predation than wild salmonids, and that Atlantic salmon (Salmo salar) experience lower predation than Sea trout (Salmo trutta), yet telemetry studies have displayed equivocal results. Here, using a large data set on passive integrated transponder (PIT) tagged hatchery‐reared and wild juveniles of Atlantic salmon and Sea trout (25,769 individuals) we investigate predation probability by piscivorous birds (mainly Great Cormorants Phalarocorax carbo) on salmonids originating from River Dalälven in Sweden. Bird colonies and roosting sites were scanned annually (2019–2021), and the temporal dynamics of bird predation on salmonids released in 2017–2021 was assessed. Hatchery‐reared trout was clearly most susceptible to cormorant predation (0.31, 90% credibility interval [CRI] = 0.14–0.53), followed by wild trout (0.19, 90% CRI = 0.08–0.37), hatchery‐reared salmon (0.13, 90% CRI = 0.07–0.23), and wild salmon (0.08, 90% CRI = 0.04–0.14), in subsequent order. This order in predation probability was consistent across all studied tag‐ and release‐years, suggesting that the opportunistic foraging of cormorants affects the overall survival of juvenile salmonids, but that the inherent predation risk between different salmonid types differs systematically.

During 2014–2019, the prevalence of Corynosoma spp., a parasite species in great cormorants (Phalacrocorax carbo spp.) and in Baltic herring (Clupea harengus membras), was studied in the Archipelago and the Bothnian Seas of the northern Baltic Sea. These results suggest that cormorants may act as a definitive host for these acanthocephalan parasites. Adults were more infected with the parasites than juveniles, which could be due to their larger size. A lower prevalence of Corynosoma spp. in juveniles may be because smaller cormorants eat smaller fish that have less parasites. We found that the most abundant corynosoma species in both the Baltic herring and cormorants were Corynosoma semerme , whereas only a few individuals of C. strumosum and only one C. magdaleni were found. The prevalence of corynosoma in herring increased from 2014 to 2018, and individuals in the Bothnian Sea were infected less frequently than herring in the Archipelago Sea. Results also showed that infected herring individuals were generally larger than non-infected individuals, which could be explained by their size and their feeding habits. Currently, the changing environment of the Baltic Sea may cause an effect on the herring making them more susceptible to infections. Our results, therefore, emphasize the importance of the regular monitoring of infections and the parasite-host relationships in the Baltic Sea. [Display omitted] • Corynosoma parasites in herring and cormorants were studied in northern Baltic Sea. • In 2014–2019, 7002 herrings and 65 cormorants were examined for parasites by PCR. • DNA analysis revealed three species: C. semerme , C. strumosum , and C. magdaleni. • In herring, Corynosoma infections increased between 2014 and 2018 (mean PR = 0.15). • Of cormorants, PR = 0.29 were infected by Corynosomas , represented only C. semerme. [ABSTRACT FROM AUTHOR]

This study aimed to investigate how great cormorants and grey herons affect the density and trophic diversity of soil nematodes under breeding colonies located in Stawy Raszyńskie Nature Reserve (central Poland). Soil samples from the colonies were compared to control samples from adjacent areas unaffected by birds. Samples were taken at each site (two colonies and two relevant control sites) to a depth of 20 cm, and the soil cores were split into topsoil (0-10 cm) and subsoil (10-20 cm). A modified Baermann method was used to extract nematodes from the soil. The soil under nests supported more abundant nematode communities, but with a lower trophic diversity compared to the control sites. The cormorants had a greater impact on nematodes than the herons. We found that the external nitrogen input, the higher organic matter content and abundance of ammonifying bacteria, as well as the lower soil pH under the colonies than in the control sites, affected the nematode trophic groups in different ways. Compared to the control sites, there were significantly more bacterivorous nematodes but fewer herbivorous nematodes under the colonies. No predatory nematodes were found under the bird colonies and, in the case of the cormorant colony, no omnivorous nematodes. No significant differences in the abundance of fungivorous nematodes between the impact and the control plots were noticed. The results indicate that allochthonous input under bird colonies promotes microbial activity and the most opportunistic trophic group of nematodes, which may at least temporarily enhance decomposition and mineralisation processes and consequently affect nutrient cycling in the wetland soil. [ABSTRACT FROM AUTHOR]

The great cormorant [Phalacrocorax carbo (Linnaeus, 1758)] can create significant conflicts with fisheries as a result of removing significant fish biomass. This is exacerbated by recent population increase in most of Europe. This study uses long-term census, climate, and environmental data to explore the wintering dynamics and strategies of the species. In Turkey, the total overwintering population, population density, and distribution of cormorants have increased significantly. Correlations with different climatic accounted for 20% to 56% of the variation in the total number of overwintering cormorants. The total number of cormorants overwintering was positively affected by warmer weather conditions in autumn and negatively by increased snow cover in winter. The Principal component analysis identified attraction (At) and avoidance (Av) factors, a two-component solution involving 12 climate variables for choosing the wintering sites of cormorants, that explained 84.3% of the total variance in total number of overwintering cormorants. Linear regression using the scores of the At/Av climate factors predicted 59.0% of the total number of overwintering birds. Our study also demonstrates that long-term census data with both resident and winter migrant populations during the winter can be used to estimate the resident population size of the species. [ABSTRACT FROM AUTHOR]

Cormorants (Pelecaniformes) are widely distributed worldwide, occurring as coastal birds in inland waters and marine environments, and have been implicated in the transmission of some aquatic parasites. As such, the objective of the present work was to investigate the occurrence and morphological variations in Cardiocephaloides (Digenea: Strigeidae), parasites of the great cormorant Phalacrocorax carbo. The Cardiocephaloides specimens used for molecular analysis (DNA barcoding (cox1) region) were obtained from the intestines of the great cormorants collected from Mwanza Gulf in Lake Victoria. Morphological examination of Cardiocephaloides specimens showed the possible co-existence of four morphospecies belonging to the genus Cardiocephaloides. However, detailed analyses of the cox1 sequences, phylogeny and haplotypes revealed that all four morphospecies belonged to a single unknown species of Cardiocephaloides. This paper provides the first report on the great cormorant Phalacrocorax carbo, serving as the definitive host for Cardiocephaloides in freshwater systems. The findings also reveal that the diversity of Cardiocephaloides in Africa is higher than earlier reported. Moreover, it highlights the need for more research in Tanzania to divulge snail and fish species involved in the life cycles of digenean species occurring in birds and other vertebrates in aquatic environments. [ABSTRACT FROM AUTHOR]

A total of 102 pseudoscorpion specimens belonging to five species, four genera, and two families were collected in the Curonian Spit National Park (Lithuania). The genus Dinocheirus Chamberlin, 1929 and the species D. panzeri (C. L. Koch, 1836) are newly recorded from Lithuania. [ABSTRACT FROM AUTHOR]

Concentrations of 12 metals (As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb and Zn) were examined in the pectoral and thigh muscle of great cormorants (Phalacrocorax carbo). The samples were collected from Central Tisza-Jászság Nature Conservation Area in Hungary. The tissue samples were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The aim of the study was to examine the impacts of heavy metal pollution on the water birds, determine the concentrations of the abovementioned metals in the different muscle tissues of these wetland birds, and provide the basic materials for monitoring the environmental pollution. Among the investigated elements/metals, the detected concentrations of As, Ba, Cd, Co, Cr, Mo and Ni were below the detection limit. Higher concentration of Cu, Hg, Mn and Pb was measured in the pectoral muscle compared to the thigh muscle, but only in the case of Cu and Mn were found significant differences between the tissues. In the case of the Zn concentration, the higher value was detected in the thigh muscle. There were no statistical differences between males and females in either metal concentrations. [ABSTRACT FROM AUTHOR]

From 1998 to 2018, in four colonies in the southern Kanto region of Japan, 6,807 Great Cormorants Phalacrocorax carbo were banded with color bands for individual identification. During 22 years between 1998 through June 2019, 6,575 sightings of 1,783 individuals were recorded. The number of color-banded cormorants gradually increased from the beginning to the middle of that period, and then decreased in the latter half of the study period. The number of records reported by bird watchers showed a pattern similar to the number of banded cormorants. However, the decrease in the records in the latter half appeared to have been influenced by the decreasing number of reported individuals. The recorded number of cormorants decreased, reflecting the advanced age classes of the banded population. The banded cormorants were reported mainly in Tokyo, Chiba, and Kanagawa prefectures where the birds were initially captured and released, with some reports from distant locations, including Aomori Prefecture to the north and Shiga Prefecture on the Pacific coast of Honshu Island. Therefore, these prefectures were demonstrated to represent the main range of movement for the population of Southern Kanto area. Results gained by these records indicated a need for establishing a strategy to maintain long-term record keeping by observers. [ABSTRACT FROM AUTHOR]

This is the first study on the diet of the Great Cormorant wintering in Algeria. It is carried out in Beni Haroun, the largest dam lake in the country, in north-east of Algeria. The trophic menu of Phalacrocorax carbo in this lake is based on four fish species: Abramis brama, Carassius carassius, Barbus barbus and Cyprinus carpio. However, Barbus barbus and Carassius carassius represent the two most important species in Great Cormorant's diet. The total consumed biomass is 155,364.18 g, and the average biomass contained in each pellet varies between 330.7 and 2,953 g. The biomass of consumed fish varies between 36.89 g and 2,501 g. The size of the caught fish records values between 13.7 cm and 52.49 cm. The number of consumed fish per pellet varies between 1 and 9. The results show that the Great Cormorant of Beni-Haroun Dam Lake consumes between 573 g and 2,353.3 g of fish per day and between 49.8 t and 185 t each month. However, the highest value is recorded in January (between 81.5 and 300.5 t). The Great Cormorant of Beni-Haroun dam lake could have a significant impact on continental and recreational fishing at this site. [ABSTRACT FROM AUTHOR]

A series of paired-pond trials were completed during the winters of 2005 to 2008 to examine the effect of introducing artificial fish refuges on Great Cormorant Phalacrocorax carbo foraging behaviour, prey capture rates and fish losses in trial ponds, and to help refine their potential use as a tool in addressing cormorant-fisheries conflicts. Investigations comparing refuge volumes within a year provided clear evidence that larger refuges offered fish better protection than smaller ones. When compared across years, there was no clear relationship between refuge volume and prey consumption rate by Cormorants. There was, however, a very large difference in the consumption rate when ponds with no refuge were compared with any of the refuge volumes tested, suggesting that, in the absence of any other cover, the addition of even very small fish refuges can markedly reduce the quantity of fish eaten by Cormorants. Further trials indicated that introducing refuges as a single larger structure was more effective at reducing fish losses than an equivalent volume of refuge arranged as a number of smaller, widely-spaced, discrete units (>50% reduction in prey consumed per Cormorant visit). Trials further confirmed that the beneficial effects of fish refuges were not compromised by the presence of marginal habitat; indeed, prey consumption rates were >30% lower in the pond with additional simulated reed beds. The impact of refuge presence on fish loss rates varied between species, with Roach Rutilus rutilus benefitting in particular. The results are discussed in the wider context of interactions between Cormorants and their prey and with regard to the potential use of fish refuges as a management tool. [ABSTRACT FROM AUTHOR]

We analysed trends in the breeding population of Great Cormorants in Greece during the period 1988–2014 when at least 20 colonies were recorded. The number of colonies doubled over the study period reaching 14 in 2014 from seven in 1988. There was also a continuous increase in the number of nests: from 952 in 1988 to 9256 in 2014, presenting an annual change of +26.5% ± 0.05 (SD). Most of the colonies were situated in freshwater lakes, three in deltas and one on the seacoast. Nine colonies were mixed with other colonially nesting species (mostly from the Ardeidae family). Of the 14 colonies 11 were found in trees. Two colonies were situated on the ground, four in bushes, two on reed rhizome islets and one on cliff ledges. Five out of the 14 active colonies in 2014, comprising 87% of the total recorded nests, were in wetlands of low altitude (0–45 m a.s.l.). The rest were situated in mountainous wetlands at altitudes ranging from 235 to 853 m a.s.l. One colony, at Lake Kerkini, contained the majority of nests in Greece (6650, being 72% in 2014). The second largest colony, at Lake Volvi, had 900 nests, followed by the Greek part of Prespa with 625 nests (in three colonies) in 2014. The percentage of nests in newly established colonies increased after 2003, reaching its highest value (14%) in 2009. The reason for the growth in both colonies and nests over the years is attributed to the increasing availability of fish, the protection status of wetlands and the absence of disturbance. Particularly after 2002 the species increased in numbers and established colonies in new areas, which is probably related to the expanding breeding populations of the species in north-eastern European countries and a corresponding increase in wintering numbers in Greece. This needs further attention by monitoring and research. [ABSTRACT FROM AUTHOR]

Two subspecies of the Great Cormorant breed in Norway, the continental Phalacrocorax carbo sinensis in the south, along the Skagerrak coast, and the marine P. c. carbo from central Norway and northwards. Here we review the information existing until 2017 on population status and trends, breeding performance and diet of these two subspecies in Norway. The most recent national population estimates are approximately 2500 (in 2012) and 19,000 (in 2012–2014) breeding pairs of sinensis and carbo, respectively. The sinensis population established itself in 1996 in Rogaland at the south-western tip of Norway, and in 1997 in Østfold close to the Swedish border; in both areas it increased for about ten years. Since then, the numbers have stabilised. For carbo, the population increased from 21,000 pairs in the early 1980s to 27,000 in 1995, and then decreased to the current number of 19,000 pairs. Significant annual variations in clutch size and reproductive output have been observed, but the drivers of these changes have not been identified. Unidentified gadoids and Atlantic Cod Gadus morhua were the most common prey of carbo, whereas inshore species such as Corkwing Wrasse Symphodus melops, Rockcook Centrolabrus exoletus, Goldsinny Wrasse Ctenolabrus rupestris and Black Goby Gobius niger were the most common prey in the eastern Skagerrak caught by sinensis. Carbo took very large numbers of 1–3-year-old gadoids during the year, and we cannot exclude the possibility this can have local effects on fish mortality rates. [ABSTRACT FROM AUTHOR]

This study is based on recoveries of c. 86,850 Great Cormorants ringed in the Russian Federation during 1939–2014. Data were obtained from the Bird Ringing Centre of Russia. During 1939 to 2014 a total of 1667 Cormorant recoveries (1.9%) were added to the ringing database. The majority of the recoveries were made in the Caspian Sea, Azov Sea, Black Sea, Baltic Sea and in Kazakhstan inland waterbodies, including the Aral Sea (seven recoveries), Lake Alakol (46), Lake Balkhash (28), Kapchagay Reservoir (10) and Lake Zaysan (5). Non-breeding birds (assuming breeding at age > 3 years) comprised 89% of ring recoveries from 1939 to 1974, 95% from 1975 to 1990 and 100% from 1991 to 2014. This study is the first to describe the migration patterns for this species on a continental scale. From Kaliningrad in the west to Vladivostok in the east seven mega clusters of waterbodies and wetlands exist where Cormorants breed and were ringed. Although showing some overlap, birds belonging to a certain cluster were recovered in distinct wintering areas, often more than 2000 km from the breeding areas and separated by high mountain ranges. The general migration pattern is discussed for four geographic regions. The occurrence of east–west migration patterns is briefly discussed and deserves further study as well as the role of high mountain ridges possibly shaping the movements between summer and winter areas. [ABSTRACT FROM AUTHOR]

Breeding Great Cormorants Phalacrocorax carbo have been rapidly increasing in Italy since the 1990s, and have settled their colonies in sites already used by other colonial waterbirds. We investigated the patterns of interference between Grey Herons Ardea cinerea and Great Cormorants, the two species most prone to competition due to their similar preference for nest sites. The analysis of long-term population trends in colonies with both species compared to colonies without Cormorants, showed that the number of Grey Heron nests gradually decreased following the settlement of Great Cormorants. The two species exhibited a gradual spatial segregation in nest location, both horizontally and vertically, within the same colony. In some heronries we found clear examples of interaction, but we also report cases where the interaction was less clear. Thus, although Great Cormorants might be competitively dominant over Grey Herons for nest site occupancy in many of their shared colonies, the spatial competition dynamics might also be influenced by factors affecting population dynamics in the wider environment. We envisage specific observations and focus on areas with an apparent abundance of trees suitable for nesting by both species. [ABSTRACT FROM AUTHOR]

The necessity of balancing conservation issues with the protection of aquaculture activities drives research to quantify the impact of the Great Cormorant Phalacrocorax carbo and to identify the best mitigation strategies. This study aims to characterise the diet in relation to the possible impact of the Great Cormorant on the extensive aquaculture farms in Friuli Venezia Giulia region in the upper Adriatic Sea. The diet of the species was investigated by analysing 459 pellets, collected monthly during the winter 2006/2007 in the three most important roosts of the Friuli Venezia Giulia coastline. Cormorants proved to feed mainly on typical fish species of lagoon and coastal waters. By frequency, Sand Smelts Atherina boyeri (54%) and Flounders Platichthys flesus (26%) were the main prey. Flounders played an important role also in terms of biomass (35%), together with mullets (Mugilidae, 28%). Commercially-important aquaculture species (European Seabass Dicentrarchus labrax and Gilthead Bream Sparus aurata) represented only 2% and 14% by frequency and biomass. The diet analysis supports our previous studies, carried out by behavioural observations on Cormorants foraging at different depths, on interactions with the main prey and strategies of exploitation of the fish farms. Our data imply that the Great Cormorant does not have a large effect on aquaculture yield in the north Adriatic Sea. [ABSTRACT FROM AUTHOR]

The recent increase in Cormorant numbers in the UK and the increasing use of inland feeding sites by the birds have created conflicts at many freshwater fisheries. Information on the prey composition of Cormorants foraging at such sites is important in understanding these conflicts and in providing a sound basis for management. Two subspecies of Great Cormorant, the continental subspecies Phalacrocorax carbo sinensis and the Atlantic subspecies Phalacrocorax carbo carbo occur in the UK and forage sympatrically. This study presents information on the winter diet of over 1400 Cormorants shot at inland fishery sites over an eleven-year period. A wide range of prey species were identified, but five fish species compromised almost 80% of the prey items recorded by number, and most prey items were small (≤10 cm). Dietary differences, in terms of the species, sizes and number of fish consumed, were apparent between birds of different sex and subspecies, consistent with the differing sizes of the birds. The largest birds (male P. c. carbo) tended to consume fewer, larger fish and the smallest birds (female P. c. sinensis) more, smaller items. Bird size also appears to influence foraging site selection, with male P. c. carbo more likely to forage on fisheries, such as put-and-take trout fisheries, where larger prey items were available. [ABSTRACT FROM AUTHOR]

Aquatic habitats are subject to multifactorial changes including global warming, invasive species colonisation, modification of organic and micro-pollutant discharge and, for large rivers in Europe, drastic physical modification (e.g. channelisation, impoundments). The Meuse River in Belgium is one of these multi-stressed environments, in which recent decreases of fish populations were observed, with the loss of 90% of Roach Rutilus rutilus biomass in only a few years. In the light of this fish stock collapse, diet modification and local population evolution of a key avian predator, the Great Cormorant Phalacrocorax carbo, were examined. The diet composition and daily consumption rates of the Great Cormorants feeding in the river were largely similar to that seen before the fish population collapsed. Numbers of wintering Great Cormorants decreased by 90%, as did Roach numbers, and thus the predation pressure was adjusted to the decreased fish availability. The number of night-roosts and locations remained unchanged and no redistribution to adjacent habitats was observed at the regional scale. We suggest a bottom-up chain of responses where a fish collapse forced a reduction in Cormorant numbers, being the main piscivorous avian predator, rather than a modification of Cormorant prey composition and/or a local redistribution to adjacent wetlands (top-down). The factors that govern the establishment of a small and productive breeding population remain to be explained, but we hypothesise that the start of breeding could well have been alleviated by the large decrease in number of wintering birds. [ABSTRACT FROM AUTHOR]

Avian species have a variety of antipredator strategies in response to predator threats of different levels. Mobbing behaviour is most common in colonial birds, although the defensive behaviour and interspecific relationships in mixed-species colonies composed of non-mobbing species are still unclear. In a mixed-species colony of Great Cormorants Phalacrocorax carbo and Grey Herons Ardea cinerea, we investigated defensive responses to potential avian predators and to actual avian predators. Our observations revealed that the birds distinguished between potential predators and reacted to particular predator species that could prey on large birds. Moreover, we found that the two colonial species showed different defensive antipredator behaviours: Herons exhibited aggressively defensive behaviours; whereas Cormorants, though vigilant, remained on the nest. To our knowledge this is the first report to suggest the possibility of commensalism in the Phalacrocoracidae, whereby Great Cormorants benefit from the defensive behaviour of Grey Herons. [ABSTRACT FROM AUTHOR]

Aim. To research the Great Cormorant (Phalacrocorax carbo L., 1758) ecology during the secondary expansion of the Baikal region.Material and Methods. The material for studying cormorant nutrition was 28 stomachs of harvested birds, visual observations of feeding cormorants using optical equipment, as well as regurgitated burps of nutrition obtained by a bloodless method when being fed to chicks. 21 examples of cormorants were the subjects of the parasitological research.Results. The number of the species has been growing since the beginning of the XXI century and, starting from 2020/21, is likely to stabilize, remaining at a high level. This indicates the gradual integration of the species into the Baikal Lake ecosystem. The main food item of Cormorants are the non‐commercial fish, Sleeper (Percottus glehni Dyb.), Perch (Perca fluviatilis L.) and Roach (Rutilus rutilus L.). Parasitological studies have revealed 8 species of helminths from three classes with varying degrees of invasion. Only one of them, Contracaecum osculatum baicalensis (Mosgovoy et Ryjikov, 1950), is endemic and potentially dangerous to human health (its infection rate can reach 80%).Conclusion. The Great Cormorant is an obligate, but not a specialized ichthyophage, focused on the prevailing fish species. Great Cormorants as hosts of ticks, helminths and other ecto‐ and endoparasites are potentially sources of threat to the occurrence and spread, primarily, of ornithoses and helminthiasis in the Baikal region and possibly of other diseases carried from their wintering places.

Wild birds are recognized as disseminators of antimicrobial-resistant (AMR) bacteria into the environment. Here, we isolated AMR indicator bacteria from 198 Great Cormorant cloacal swabs collected in Shiga (n=90), Oita (n=52), Gifu (n=29), and Gunma (n=27) Prefectures, Japan, in 2018 and 2019. In total, 198 Aeromonas spp. and 194 Escherichia spp. were isolated, and their antimicrobial susceptibility was examined. Aeromonas spp. were resistant to colistin (8.6%), nalidixic acid (4%), and other antimicrobials (<2%), with 3.0% positivity for mcr-3. Escherichia spp. showed resistance to colistin (3.1%), ampicillin (2.6%), tetracycline (2.1%), and other antimicrobials (<2%). This study shows the presence of AMR bacteria in Great Cormorants, indicating that these birds potentially disseminate AMR bacteria. [ABSTRACT FROM AUTHOR]

Globally, the establishment of protected reserves contributes positively to species protection but also presents a real threat of unexpected changes. A few reports showed that progressively increasing the number of roosting and breeding cormorants across Europe was associated with food-rich water bodies. Our studies concerned detailed and novel research on annual cyanobacterial growth against other ecological factors, that is, biotic (ciliates, rotifers, cladocerans, and copepods) and abiotic (temperature, nutrients) factors, in a lake where the piscivorous great cormorants evidently affects the water quality. Mass development of cyanobacteria lasted throughout the whole of the ice-free months (March–December). However, in the under-ice period they also formed a relatively high biomass, suggesting an annual persistence. The potentially toxic filamentous Pseudanabaena, Aphanizomenon, Planktothrix, and Limnothrix were constant dominants in the cyanobacteria-dominated phytoplankton almost year round. Water temperature played a major role in stimulating the growth of filamentous cyanobacteria. However, nitrogen, phosphorus, and even some zooplankters were significantly related to cyanobacteria. A very low trophic efficiency suggested a reduced energy flow at a lower food-web level starting from dominant cyanobacteria. Our results also suggest that numerous breeding colonies of great cormorant contributed to bottom-up (nutrients) and top-down (predation on fish) controls and consequently to the formation of a site-specific refuge for filamentous cyanobacteria. This affects the functioning of the water ecosystem by disturbing the energy flow in the classical food webs, which is important in water management and warming-induced global problems with cyanobacterial dominance and water quality.

Wintering waterbirds were censused and the effect of ice cover on their abundance was studied on the Hron River (Slovakia) in mid-January 2007–2020. Altogether 24 sites along a 90-km stretch of the middle part of the river was surveyed, of which 23 were sites with running water (81 ha) and one with stagnant water (Kozmálovce reservoir; 63 ha). A total of 25 waterbird species (annual mean 11.2) and 19,645 individuals (annual mean 1,405) were recorded. Mallard (Anas platyrhynchos; relative abundance 86.4%), Great Cormorant (Phalacrocorax carbo; 8.7%), Common Merganser (Mergus merganser; 1.6%) and Grey Heron (Ardea cinerea; 0.8%) were the most abundant species. During the 14-year period, the Great Cormorant abundance decreased, while the abundance of Mallard, as well as total abundance of the whole assemblage of 25 species remained stable. In the entire study area (all the 24 sites pooled), only the abundance of Common Goldeneye (Bucephala clangula) negatively correlated with the ice cover. Within a subset of sites with running water, the abundance of Mallard and Mute Swan (Cygnus olor), as well as the total abundance of 18 species recorded here positively correlated with the ice cover. At the site with stagnant water, the abundance of Mallard, Common Merganser, Common Goldeneye, Great Cormorant and Grey Heron, as well as the total abundance of 21 species recorded here negatively correlated with the ice cover. This supports the importance of running water as a “cold weather refuge” for wintering waterfowl. [ABSTRACT FROM AUTHOR]

The Mediterranean shag (Phalacrocorax aristotelis desmarestii) and the great cormorant (P. carbo sinensis) are syntopic birds in an area encompassing Grosa Island and the Mar Menor coastal lagoon (SE Spain, western Mediterranean) during the breeding season of the former and the wintering period of the latter. Diet composition of both birds was studied through pellet analysis and otolith identification. Competition for fish resources between these two seabirds and with local artisanal fisheries was assessed. Shags preyed preferentially on small pelagic fish, and great cormorants mainly consumed demersal fish. Shag diet consisted of marine fish strictly, but great cormorant fed in all the available environments in the study area, including marine, transitional (coastal lagoon) and freshwater reservoirs. The great dissimilarity observed between shag and great cormorant diet composition showed no competition between them. The low shag population density and fishing effort in their foraging area suggested no competition with fisheries. Conversely, great cormorant population density in the study area was very high, and they foraged on fish of high commercial value. However, competition between great cormorant and artisanal fisheries only affected some of the less abundant species fished.

The webbed feet of waterbirds are morphologically diverse and classified into four types: the palmate foot, semipalmate foot, totipalmate foot, and lobate foot. To understand the developmental mechanisms underlying this morphological diversity, we conducted a series of comparative analyses. Ancestral state reconstruction based on phylogeny assumed that the lobate feet possessed by the common coot and little grebe arose independently, perhaps through distinct developmental mechanisms. Gremlin1, which encodes a bone morphogenetic protein (BMP) antagonist and inhibits interdigital cell death (ICD) in the foot plate of avian embryos, remained expressed in the interdigital tissues of webbed feet in the duck, common coot, little grebe, and great cormorant. Differences in Gremlin1 expression pattern and proliferating cell distribution pattern in the toe tissues of the common coot and little grebe support the convergent evolution of lobate feet. In the totipalmate-footed great cormorant, Gremlin1 was expressed in all interdigital tissues at St. 31, but its expression disappeared except along the toes by St. 33. The webbing of the cormorant's totipalmate foot and duck's palmate foot may have risen from distinct developmental mechanisms. [ABSTRACT FROM AUTHOR]

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Since in 1980s, the number of great cormorants (Phalacrocorax carbo sinensis) has increased all over its European distribution area. This has led to conflicts between bird conservation and fisheries. Mariager fjord in Denmark is an important feeding and transition area for a large population of migrating seatrout (Salmo trutta), but it also provides resting and breeding places for cormorants. Thus, juvenile anadromous salmonids migrating from the river to the sea may be exposed to high predation risk during a critical and vulnerable time in their development. A total of 31 123 down-migrating wild seatrout were tagged with Passive Integrated Transponder (PIT) tags in 2008, 2009, 2015, and 2016 in river Villestrup, the main tributary flowing into Mariager fjord. Tagged fish were measured and grouped by their developmental stage as parr, pre-smolt, or smolt. To quantify cormorant predation, nearby cormorant colonies and roosting sites were repeatedly scanned for PIT tags with a manual antenna to record tags from predated fish. Minimum predation rate was 27% but varied among years. Body length of the fish and predation risk were negatively correlated and the latter was dependent on the group of the fish. This study demonstrates a potential negative effect of predation by great cormorants on an important population of wild trout. [ABSTRACT FROM AUTHOR]

The breeding ecology of the Great Cormorant, Phalacrocorax carbo, was surveyed by using color marking and trail cameras at a cormorant breeding colony in Horonobe, northern Hokkaido from 20152019. In May 2015 cormorants abandoned their nests, although the process from courtship to incubation was recorded by trail cameras. Hence color marking was not conducted. In April 2016, cormorants also abandoned nests, and one raccoon, Procyon lotor, was photographed only at night when cormorants appeared at the colony. No cormorants were confirmed at the breeding colony from 2017 to 2019. Nesting abandonment in 2015 and 2016 probably occurred as a result of disturbance by raccoons. [ABSTRACT FROM AUTHOR]

THE ASSOCIATION between Dalmatian Pelicans Pelecanus crispus and Great Cormorants Phalacrocorax carbo was studied at three Greek sites, Megali Prespa, Kerkini and Karla. At Prespa, the two species seemed to use each other mutually: pelicans benefited from fish that tried to escape from the cormorants by swimming towards the surface while cormorants used the pelicans as a cue to the presence of fish shoals. When a pelican flew towards a cormorant, other cormorants immediately flew there and dived instantly. The association usually was very brief, lasting only a mean of 114 seconds. Pelicans mostly foraged singly or in small groups (mean 3.2 individuals) and often there were also few cormorants (median 6). Kleptoparasitism was recorded at all three sites, but at Kerkini and Karla, pelicans associated with the huge fishing flocks of cormorants and predominantly kleptoparasitized them. Around 20% of attacks were successful. Thirty-one attacks were very violent with the pelican holding the cormorant until it dropped its fish. [ABSTRACT FROM AUTHOR]

The genus Eustrongylides includes nematodes known as the etiological agent of the ‘‘big red worm disease.’’ The aim of this work was to identify Eustrongylides spp. larvae from fish and adults from great cormorant (Phalacrocorax carbo) sampled at Lake Trasimeno, Italy, by morphological and molecular analysis. Histopathological description of the lesions in birds was also provided. We described adults of Eustrongylides excisus for the first time in Italy, and we also linked larval stages 3 and 4 to adults. The use of molecular tools combined with the traditional taxonomy will help the identification of the species, including species inquirendae. Moreover, molecular analysis can also help to investigate the role of intermediate and paratenic hosts, to deepen the knowledge about geographical distribution of the different Eustrongylides spp. and to define the zoonotic potential of E. excisus, which has not yet been identified as causal agent of human cases. [ABSTRACT FROM AUTHOR]

Since the mid-1980s, there has been a steady rise in the numbers of great cormorants in all Eurasia, and in the number over-wintering annually in Israel. Winter counts in recent years show about 15,000 - 20,000 great cormorants in Israel; they arrive in October and stay until March. Over the years, colonies of over-wintering great cormorants, which can have over 5,000 individuals each, come into conflict at commercial fish farms in Israel, which are in the form of local concentrations of open earthen ponds, in which are grown very high concentrations of food fish, mainly carp, tilapia, grass carp, and mullet. Over the years, many attempts have been made to reduce the negative impact of over-wintering great cormorants on the commercial fish farms in Israel, utilizing lethal and non-lethal methods. Over 50 banding returns from the last 2 decades showed that the great cormorants over-wintering in Israel originated in the area around the northern Black Sea and Sea of Azov, around the Crimean Peninsula in southern Ukraine (about 1400 km or 850 miles due north). This overabundant species causes considerable damage around its nesting sites in Ukraine by interfering with endangered waterbirds, and by conflicting with fishermen. Israel has recently been exploring ways to utilize international cooperation for management of the nesting population in Ukraine, in order to reduce the size of the wintering population in Israel and also to prevent damage to endangered waterbirds in Ukraine. The major instruments are the European Union’s project INTERCAFE (Interdisciplinary Initiative to Reduce Pan-European Cormorant-Fisheries Conflicts: www.intercafeproject.net), and the African-Eurasian Waterbird Agreement (AEWA) under UNEP’s Convention on Migratory Species (CMS): www.unep-aewa.org, as well as other International Environmental Agreements. An experimental program is proposed for reducing the nesting success of the Ukrainian population. A smaller great cormorant population should impact less upon nesting waterbirds in Ukraine and also decrease the intensity of the conflict with both Ukrainian and Israeli fishermen, thereby lessening the extent of lethal control used against great cormorants in both countries. The proposed experimental program includes egg-oiling of ground-nesting birds and hazing tree-nesting birds with green lasers.

Anthropogenic debris is rapidly spreading in marine environments and poses major problems to biodiversity and humans. However, mitigation strategies are limited by the lack of information on the accumulation patterns of these pollutants both at sea and in marine wildlife. Using observations from an uninhabited island in Delta du Saloum National Park, Senegal, we investigate here the prevalence and abundance of debris in nests of two sympatric seabird species, Caspian terns Hydroprogne caspia and great cormorants Phalacrocorax carbo , and its potential as an indicator of ocean pollution. We recorded debris in 15% of the Caspian terns' nests, and 40% of the great cormorants' nests. Plastics accounted for > 95% of items recorded in the nests of both species. Caspian terns collected a diverse array of debris, both in terms of types and colours, with a preference for hard plastics and white items. The great cormorants accumulated in nests mainly greenish fishing gears resembling the vegetation typically used as nest materials. Nests of both bird species contained soft plastic in proportions lower than those observed in the environment. Our results suggest that nests of Caspian terns and great cormorants are not useful indicators of pollution by anthropogenic debris in the surrounding waters of the Delta du Saloum National Park. Nests of great cormorants, however, have the potential to indicate areas vulnerable to plastic pollution associated to fishery. The high amount of debris in nests of this species demonstrates the need for a better implementation of waste management strategies in Senegal. • We assessed the prevalence and abundance of litter in nests of seabirds in Senegal. • Litter was present in 15% (Caspian terns) and 40% (great cormorant) of nests. • Plastic accounted for > 95% of items in nests of Caspian terns and great cormorants. • Plastic types and colors in nests are not the same as in the surrounding environment. • Great cormorant' nests indicate areas subjected to pollution associated to fishery. [ABSTRACT FROM AUTHOR]

We compared the concentrations of 17 heavy metals and essential elements in post-hatching eggshells of two waterbirds, the obligate piscivorous great cormorant Phalacrocorax carbo (GCM) and the more omnivorous grey heron Ardea cinerea (GHR), breeding sympatrically in eight mixed colonies in Poland. We found significant inter-species and inter-colony differences in the levels of most of the elements. GHR had significantly higher concentrations of Al, which can be explained by its very low stomach pH: an acidic environment favours the release of Al compounds. Differences in Mn, Ni, Cu, Se and Hg concentrations can be attributed to the various contributions of fish and other aquatic organisms to the diet, and to the exploration of different habitats (GCM exclusively aquatic, GHR a wider range) and microhabitats (GCM, in contrast to wading GHR, dive for food, exploring the whole depth range of water bodies), differently exposed to contamination by those elements from sediments. Inter-colony differences were related to the level of industrialisation. We recorded higher levels of some elements in the eggshells (Fe, Mn in both species and Cr, Ni and Zn in GCM) collected in industrialised areas, which may be associated with the negative environmental impact of industrial areas. [ABSTRACT FROM AUTHOR]

Abstract Harmonizing biodiversity conservation and natural resource management often requires anticipating the potential impact that certain species can cause through their exploitation of specific resources. During the winter 2008/2009 we studied the feeding ecology of the Great Cormorant Phalacrocorax carbo sinensis in SE Spain, in order to determine its dependence on different food sources available along an oceanic-continental gradient (open sea-freshwater bodies). Trophic niche was assessed using C and N stable isotopes, applying up-to date metrics and analytical tools. Isotopic signatures revealed high mobility patterns for cormorants, illustrating differences between roosting and feeding areas (spatially well separated). Cormorants roosting in open sea move to inland freshwater bodies, their trophic niche overlapping that of individuals settled there. Similarly, individuals settled around transitional waters (coastal lagoon), seem to divide the predation pressure between different food sources along the marine-continental gradient. Recently in Spain, the Great Cormorant has been devoid of legal protection due to its supposed impact on fisheries. Our methods provide a useful and non-invasive tool that can be used as a first step for assessing such interaction. On the basis of its dispersed feeding distribution and expected predation pressure the cormorant does not seem to represent a serious threat to recreational or commercial fisheries which would justify downgrading its protection. Highlights • Trophic niche of Great Cormorants was assessed using C and N stable isotopes. • Isotopic signatures revealed high mobility between roosting and feeding areas. • Feeding pressure seems to be spread among habitats in a marine-continental gradient. • Downgrading the level of protection of Great Cormorants seems unjustified. [ABSTRACT FROM AUTHOR]

Herons and Great Cormorants Phalacrocorax carbo nested at Chikubushima Island in Lake Biwa, Japan, during the Edo and Meiji periods(18th century - early 20th century). Local residents had much experience with these bird species and a deep folkloric knowledge. The local residents ate the eggs and meat of these birds, and used their feathers for fishing gears and other purposes. Some of them caught the young cormorants and trained them for "cormorant fishing" in Fukui, in the Japan Sea side. However, from the middle of the Showa period(the mid-1900's)they no longer utilized these bird species, even after the population increase of these bird species during the 1990s. [ABSTRACT FROM AUTHOR]

Having examined 19 great cormorants (Phalacrocorax carbo) hunted in Lithuania, sarcocysts were found in the muscles of two birds. Sarcocysts detected were examined using light microscopy (LM), transmission electron microscopy (TEM), and 18S rDNA, 28S rDNA, ITS1, cox1, and rpoB sequence comparison. Based on the molecular analysis, mainly of the ITS1 region, sarcocysts were identified as Sarcocystis halieti. This is the first Sarcocystis species characterised in the great cormorant. Under the LM sarcocysts were ribbon-shaped, very long and thin (the largest fragment found amounted to 6.5 × 0.1 mm) with a smooth and thin (up to 1.2 μm) cyst wall. Banana-shaped bradyzoites were 7.2 × 1.9 (6.3-8.2 × 1.4-2.4) μm. Under TEM, the cyst wall was wavy, 0.8- to 1.2-μm thick. The comparison of 12 species demonstrated cox1 and rpoB to be unsuitable for the identification of Sarcocystis spp. using birds as intermediate hosts. [ABSTRACT FROM AUTHOR]