Great Cormorant Phalacrocorax Carbo Research Articles

Numbers of Great Cormorants Phalacrocorax carbo Wintering in the Western Palaearctic in January 2013

Great Cormorants were censused on a pan-European level in January 2013. Cormorants were found in an enormous winter range, spanning from the Baltic Sea and Atlantic Ocean in the north to the Mediterranean and coasts of North Africa. This large-scale exercise in which more than 5000 volunteers took part resulted in a total of 641,650 Cormorants counted (630,000–672,000 estimated). Based on the breeding census data of 2012 we estimated a total number of birds in January 2013 of slightly over 1 million, including the birds from the Ukrainian and Russian parts of Black Sea, Sea of Azov and north-western Caspian. Using the summer counts to produce a corrected estimate for the area that was actually covered during the winter count gave an estimated 695,000 individuals for January 2013. Total coverage was considered good and comparison to the previously conducted winter count of 2003 revealed, corrected for coverage, a 15% increase. As both counts were carried out during a period of cold weather, it is unlikely that birds were missed due to movements to the east and north-east of the range, from or into areas that are difficult to assess. Some 33% of all Cormorants were found to occur in areas with a temperature of –5°C or lower, suggesting that many birds can survive under conditions that may be marginal, i.e. at a high risk and/or cost. Compared to the previous count a relatively lower number of Cormorants were found under low temperature conditions, –5 °C down to –10°C, coinciding with the moment of active ice formation of shallow and stagnant freshwaters. It may well be that the actual ice cover in 2013 was such that birds had to leave these areas. In contrast to the opinion that wintering under low temperatures is marginal, it is possible that these northerly wintering grounds are more rewarding in terms of food profitability. This is because cold-blooded fishes congregate at certain spots and are less mobile at low temperatures and thus relatively easy to catch. Given the current and previous work carried out we recommend a long-term monitoring of these processes, which operate at a huge geographic scale. A repeated pan-European count with intervals of about ten years could detect the major patterns, while also providing a useful method of monitoring changes due to the expected further warming of winter conditions.

Natural Regulation of the Baltic Population of the Great Cormorant Phalacrocorax carbo sinensis: The Interplay between Winter Severity and Density Dependence

After a period of continuous increase and range expansion, the Baltic Great Cormorant population has stabilised in large parts of its range in recent years. Ringing recoveries reveal that considerable proportions of the population winter in areas that can be affected by prolonged frost periods. There is evidence that winter severity is an important density-dependent regulation factor: if the population is large, ice cover of coastal and inland water surfaces during harsh winters affects the population by reducing the availability of food resources. As long as the population remained small, however, it was not affected even by very cold winters, since the remaining accessible food resources were presumably still sufficient. The analysis presented here uses the average winter temperature in Germany as a proxy for winter severity in the frost-affected parts of the wintering areas of Baltic Cormorants. The Baltic Cormorant population in 1980–2016 is estimated from annual counts in Denmark, Schleswig-Holstein, Mecklenburg-Western Pomerania, Estonia, Finland and Gotland, which account for about 50% of the total population. The interplay between winter severity and density dependence is analysed using a linear and a non-linear regression model approach. The non-linear model gives a better description of the relationship between the size of the Baltic breeding population during the year (n), the winter temperature Tn, and the population size during the previous year (n–1). According to the model, a population of less than 41,400 breeding pairs would not suffer declines during even the coldest winters recorded since 1882. In 1989, the Baltic Cormorant population exceeded for the first time the threshold value for density-dependent regulation caused by severe winters. The winter 1995/96 was then the first one cold enough to cause a population decline. According to the model, during the years 2002/2003, 2005/06, 2008/09, 2009/10 and 2010/11 the winters have been cold enough to reduce population numbers. Furthermore, the model shows that the regulative winter effect is restricted to the low temperature range.

Great Cormorants Phalacrocorax carbo in the Subalpine Soča River System, Slovenia: The Possible Effect of Avian Predators in a Sensitive Biogeographic Region for Fish

The foraging of Great Cormorants Phalacrocorax carbo in Alpine rivers is a relatively recent phenomenon. Wintering populations in Slovenia increased in the 1980s. In the 1990s, the increase affected the upper sections of rivers where the habitats of Grayling Thymallus thymallus and trout Salmo and Oncorhynchus spp. are located. The upper section of the Soča River system is known as one of the biogeographic hotspots for (sub)alpine rivers, where several endemic or rare fish species are found. The aim of this study is to evaluate the diet of the Cormorants in this area and to compare it to some other threats to the fish fauna of the river. A total of 75 Cormorant stomachs were examined. Of these, 68 (90.7%) contained fish or recognisable fish remains. The birds' diet consisted of eight species of fish: Marble Trout, Rainbow Trout, Common Nase, Vairone, Common Chub, Italian Chub, Italian Barbel and Bullhead. The increase in numbers and the diet of Cormorants in the river basin of Soča is discussed in the context of the increase of other threats to this ecosystem, such as fish stocking, gravel extraction and tourism, especially angling and water sports. A more comprehensive environmental assessment of all these factors is needed, as their increase runs parallel with the arrival of the Cormorants in the upper section of the river. There is therefore reason to believe that Cormorants are only a small part of a larger problem in the conservation of the river ecosystem.

Conspecific Density as a Driver of Offspring Body Condition in Three Cormorant Colonies in Denmark

Density-dependent depletion of prey during the breeding season may affect breeding performance and colony development in seabirds and colonial waterbirds. Breeding Great Cormorants Phalacrocorax carbo sinensis are central place foragers, so parental flight distances to profitable foraging grounds and thus parental provisioning of offspring are likely affected by local food availability. Chick body condition in a given colony may therefore be influenced by the distance to feeding areas, changes in fish stocks and fish distribution as well as the number of Cormorants from neighbouring colonies using the same feeding areas. At three Danish Great Cormorant colonies with overlapping foraging ranges and variable access to shallow marine areas, Vorsø (VO), Mågeøerne (MA) and Stavns Fjord (SF), we investigated variation in mean chick body condition (n = 9697) in relation to colony location, year, colony size and estimated density of foraging conspecifics during 1993–2007. Foraging areas available to VO colony parents had the highest theoretical densities of conspecifics and the VO chicks were invariably in poorer condition than the chicks at the other two colonies. Chick body condition was negatively correlated with estimated foraging density, especially within a foraging range of 20 km. Body condition between all three colonies was weakly correlated over the years, suggesting that changes in macro-environmental conditions (e.g. fish density) only had moderate impacts on food availability, independently of Cormorant numbers. We conclude that both the geographical location of colonies, the size of the colony itself and the nearest neighbouring colonies and the associated variation in density of foraging Cormorants were major drivers of variation in chick body condition between colonies and years.

Migration Patterns and Recorded Emigration of the Great Cormorant Phalacrocorax carbo sinensis in the Largest French Colony of Lac de Grand-Lieu: Density-Dependent Factors Operating at Different Time and Geographical Scales

The number of wintering Great Cormorants Phalacrocorax carbo sinensis in France has strongly increased since the 1970s, mainly due to the protection of the ‘continental’ sinensis subspecies in countries north of France. This increase has led to the establishment of a pioneering inland breeding colony in western France, while previously only the largely marine ‘Atlantic’ P. c. carbo subspecies occurred on the Channel coast. The marine subspecies was attracted and bred in this new inland settlement of sinensis, which rapidly became the largest colony in France. This paper analyses the migration pattern of birds from this colony by analysis of the dispersal of colour-ringed birds between 1989 and 2008. Interestingly, besides a classic south-west migration pattern, birds from this colony also displayed a pattern heading north-east, up to countries such as The Netherlands, from where the founders (sinensis) of this colony probably originated. Sightings and recoveries revealed that about 25% of the adults and 19% of the first-year birds headed north-east. Due to this north-east migration direction, the overall annual dispersal point was located only 50 km south-west of the colony, although in December and January this midpoint was located about 320 km south-west of the colony. The birds largely avoided Brittany, presumably to avoid competition with individuals of the carbo subspecies, and the main wintering areas of sinensis from other colonies, both in France (east, centre and south) and in Spain. Over the years 1989–2008, in the breeding period, the mean dispersal distance was shorter for adults than for young birds (54 km vs. 144 km, respectively) but in winter adult birds migrated further than young ones (305 km vs. 221 km, respectively). The mean annual dispersal distance in winter varied from 106 km to 527 km (all age-classes taken together). Migratory distance was not related to mean winter temperature. For adults, dispersal distance correlated with the annual number of breeding pairs in the Grand-Lieu colony between 1990 and 2003, but not between 2004–2008. Emigration (breeding in another colony) was recorded up to 2011 to 11 inland colonies and one coastal colony (founded more recently than Grand-Lieu), nine of them in France, two in Spain and one in The Netherlands. Annual emigration rate was negatively related to colony size in Grand-Lieu. The study points to the existence of density-dependent effects on distribution patterns of Cormorants outside the breeding season but also suggests connectivity and interaction among colonies that are hundreds of kilometres apart.

Molecular Methods to Study Great Cormorant Feeding Ecology

The feeding ecology of the Great Cormorant Phalacrocorax carbo has been the subject of many studies in which the hard parts of fish, contained in dietary samples such as regurgitated pellets, were identified using morphological characteristics. However, morphological prey identification does not necessarily permit the reliable identification of all fish species due to digestion eroding diagnostic characters and/or morphologically indiscernible hard parts in a range of fish species. Molecular methods have the potential to overcome these obstacles by allowing the detection and identification of minute quantities of prey DNA present in pellets, faeces, and stomach samples. Moreover, DNA of the consumer (i.e. the Cormorant) is also present in dietary samples and can thus be employed for ecological studies too. Here, we present a methodological overview of two molecular approaches commonly used to study trophic interactions, namely diagnostic PCR and next generation sequencing, along with their main advantages and disadvantages. Regarding the use of consumer DNA contained in dietary samples, molecular sexing, i.e. the non-invasive sex determination of the sample-producing bird, is presented. We exemplify the potential of DNA-based methods for future research via a case study on pellets collected at Chiemsee (Germany), which were subjected to molecular and morphological prey identification as well as to molecular sexing. Compared to morphological prey identification, molecular analysis led to a 53% increase in prey species and genera, mainly caused by eight additionally detected cyprinid taxa. For 79% of the pellets, the sex of the pellet-producing Cormorant could be successfully determined via molecular sexing. Our findings highlight the exciting possibilities molecular methods offer for future studies on Cormorant feeding ecology, especially regarding evaluations of prey spectra and the non-invasive assessment of sex-specific differences.

Diet of Great Cormorants Phalacrocorax carbo in Relation to Fish Resources in the Upper Adriatic Sea

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.

GPS-Tracking of Great Cormorants Phalacrocorax carbo sinensis Reveals Sex-Specific Differences in Foraging Behaviour

Great Cormorants Phalacrocorax carbo sinensis are considered generalist predators feeding in a variety of marine and freshwater habitats on many different prey species. Recently however, there is increasing evidence that even seemingly generalist species can often be regarded as a diverse group of individual specialists sometimes induced by sex-specific foraging behaviour. To test whether this also holds true for Great Cormorants, the present study characterised the at-sea distribution and examined the time budgets of provisioning Great Cormorants by deploying GPS-loggers on 11 nesting males and females during the breeding season of 2012. Additionally, pellets were collected from underneath the nests of these tagged birds for detailed diet analysis, based on the otoliths and fish bones recorded within them. Diverse foraging patterns were recorded, ranging from exclusively freshwater feeding, to offshore foraging, with the furthest recorded distance from the colony being 28 km at sea. Time budgets during foraging trips revealed relatively long periods of resting ashore (55% of the trip ± 23%), followed by foraging (31 ± 18%), and time spent in flight (15 ± 11%). Flatfishes dominated in the diets of these Great Cormorants, indicating benthic-foraging strategies when foraging in saltwater (feeding on discards could be ruled out). The males in this study avoided freshwater foraging habitat and preferred offshore waters with a sandy bottom or nearshore waters alongside rocky breakwaters and within harbours. Females foraged in all habitat types, but proportionally more in inland freshwater bodies. Females spent more time on foraging than did males, particularly in marine habitats, whilst males rested more. It is proposed that these differences might have been caused by sex-specific foraging strategies, possibly resulting from competition at foraging sites.

There must be Some Kind of Way Out of Here: Towards ‘Reframing’ European Cormorant-Fisheries Conflicts

One of the most widespread and persistent environmental conflicts in Europe involves the Great Cormorant Phalacrocorax carbo. The ‘continental’ race P. c. sinensis comprises over 80% of the European breeding population and its numbers and geographical distribution have increased and expanded dramatically in recent decades. Consequently, Cormorants have increasingly come into conflict with fisheries interests across Europe, as many people believe that the birds are now so numerous that they cause declines in fish catches, with associated impacts on commercial and recreational fisheries. The Central European policy issue is thus how to deal with: (1) a large pan-European population of Cormorants, (2) very often breeding in some Member States but overwintering and preying upon fish in others, (3) where there is generally a lack of unequivocal scientific evidence for predation impact on fisheries and (4) where there are growing political calls for coordinated European management, whilst (5) many believe that the site-specific local/regional management advocated by some is ineffective. Using case examples and experiences from several pan-European studies and research networks, this paper describes the complexity of this issue and the diversity of associated opinions. Much of the controversy over Cormorants is fuelled by differences of opinion and, coupled with its persistence and entrenched nature, it has many of the characteristics of a so-called ‘intractable environmental conflict’. As such, this paper draws on a ‘reframing’ model proposed to deal with such situations and discusses the various ‘frames’ by which issues are viewed. It also proposes that future research might best focus on specific fisheries sectors that appear to be ‘hotspots’ for conflicts. Here, demonstration projects could involve a reframing exercise, coupled with new scientific research and practical experimentation within an adaptive management framework – one aim of which might be to increase the scope and geographical coverage of effective management activities.

Reducing Fish Losses to Great Cormorants Using Artificial Fish Refuges: Refining Refuge Deployment Strategies

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.

Winter Diet of Great Cormorants Phalacrocorax carbo in the River Geul, The Netherlands: The Importance of Common Small Riverine Fish Species

Since 2006, Great Cormorants Phalocrocorax carbo sinensis have wintered in the area of the river Geul, a right-bank tributary of the river Meuse, in the province of Limburg in the south of The Netherlands. Although the number of birds there is relatively small (approximately 30 birds), the local sports fishery sector is concerned about the possible impact on wild Brown Trout Salmo trutta, particularly on the young year-classes, through predation by wintering Cormorants. The number of birds, as well as their estimated fish consumption, was studied in the winter of 2012. Analysis of 70 diet samples (pellets) taken from the roost local to the area, showed that predation was primarily on young year classes of cyprinids, like Roach Rutilus rutilus. These cyprinids, and probably also the few trout consumed, were thought to have been mainly taken from farmed fish ponds in the direct neighbourhood of the river Geul. Besides predation of larger cyprinids, the Cormorants also took abundant small riverine fish species (2–10 cm) like Rhine Sculpin Cottus rhenanus and smaller cyprinid species like Minnow Phoxinus phoxinus and Gudgeon Gobio gobio. These riverine fishes have increased recently due to ameliorated water quality. The estimated fish consumption by Cormorants in the present study suggests limited or no impact on Brown Trout during winter.

Analysis of the Recovery Data of the Great Cormorant Phalacrocorax carbo Ringed in the Russian Federation and on the Territory of Former Soviet States in 1939–2014

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.

The dominant species of piscivorous bird does not adversely affect fishery in the lagoons of the southern Baltic Sea

The impact of fish-eating birds on fishery has long been debated. It is therefore important that the arguments in this debate be scientifically based. The Great Cormorant Phalacrocorax carbo is a flagship example of a conflict species that has been well studied. In some areas, however, such as the southern Baltic estuarine lagoons, the Goosander Mergus merganser may be more abundant, exerting a potentially greater impact on fisheries. However, this aspect has not been well studied in this region, so this article is an attempt to fill this knowledge gap. Based on the digestive tract content of 23 Goosander drowned in gillnets in Poland, it was found that the most frequently consumed species was Ruffe Gymnocephalus cernua (70% of biomass), followed by Zander Sander lucioperca (13% of biomass), Perch Perca fluviatilis (9% of biomass) and Roach Rutilus rutilus (8% of biomass). Average Goosander numbers in the Vistula and Odra estuaries in 2011–2018 were 11,000 in winter, 4,500 in spring and 2,800 in autumn. These fish-eating ducks were found to consume 242 t of fish annually during this period, whereas at the same time fishermen caught an average of 4,400 t of fish. The species caught by both Goosander and fishermen were mainly Zander (32 t vs 189 t), Perch (21 t vs 668 t) and Roach (19 t vs 701 t). No negative impact of Goosander foraging in the winter preceding the fishery season was demonstrated for any of the above species (Zander R2 = 0.022; Perch R2 = 0.834; Roach R2 = 0.881).

Fishermen's knowledge and conservation attitudes: focus on the great cormorant Phalacrocorax carbo (Linnaeus, 1758) in the Minho River, Portugal.

Considerate the attitudes of traditional communities and their local ecological knowledge (LEK) can contribute to better policymaking and more appropriate management plans. Thus, this study strived to share the Minho River’s fishermen LEK about great cormorant Phalacrocorax carbo (Linnaeus, 1758), as well as it exposes their conservation attitudes towards this species. We described and analysed interviewees’ LEK qualitatively, while their attitudes were analysed quantitatively through correlation with variables from fishermen’s profile. Fishermen were able to identify cormorant’s ecological characteristics like habitats, prey species, and foraging behaviour. They also exposed an overall moderate attitude towards the conservation of great cormorants. The LEK often was supported by published data, but we found diverse information in some themes, such as habitat and diet. We found a significant negative correlation between fishermen’s age and attitudes (p = 0.02), and those fishermen who often fished contrasted significantly from those who rarely fished (p = 0.02). We lastly reaffirm the importance of the present study as background information regarding P. carbo in Minho River and of ethnobiological studies as a tool for management plans.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10452-021-09928-4.

Asymmetric Antipredator Behaviour in a Mixed-Species Colony of Two Non-Mobbing Bird Species

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.

Stomach contents of the great cormorant Phalacrocorax carbo inhabiting northeastern Poland

Stomach contents of the great cormorant Phalacrocorax carbo inhabiting northeastern Poland

Impacts of Great Cormorant and Cattle Egret Nesting on Other Waterbirds in a Shared Breeding Site in Piedmont (NW Italy)

Some waterbird species are believed to have an impact on other waterbird species as they are able to usurp a limited habitat and destroy vegetation. In this study, we have analysed the nesting dynamics of five waterbird species: Grey Heron Ardea cinerea, Great Cormorant Phalacrocorax carbo, Little Egret Egretta garzetta, Black-crowned Night Heron Nycticorax nycticorax and Cattle Egret Bubulcus ibis, that had settled in a colony in the Royal Castle Park of Racconigi (Cuneo, NW Italy) over a 17-year period (2000 to 2017). The Great Cormorant and the Cattle Egret settled in the colony in 2008 and 2012, respectively. We analysed the relationships between the number of breeding pairs of the five species. In addition, we used the time series forecasting method to study the nesting dynamics and the impact of the new settlements on the pre-existing colony. The number of nests of the Great Cormorant and the Cattle Egret increased annually, and these species significantly affected the nesting trends of the other pre-existing species: Grey Heron, Black-crowned Night Heron and Little Egret. The Grey Heron mainly suffered from the occupation of its old nests by the Great Cormorant from 2008 to 2013. However, since 2014, the Grey Heron has been able to react, by displacing its breeding site to the tops of trees adjacent to the old heronry, and this has resulted in an even greater number of nests than before 2008. The Black-crowned Night Heron and the Little Egret suffered more from the settlement of the new species than the Grey Heron did, and started to suddenly or gradually abandon the breeding site. The colony has been modified profoundly by the settlement of the Great Cormorant and the Cattle Egret, and it is still subject to dynamics that could transform it in the coming years.

Comparison of metal burden in different muscle tissues of Great cormorant (Phalacrocorax carbo)

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.

Occurrence of echinostomatoids (Platyhelminthes: Digenea) in Great Cormorant (Phalacrocorax carbo) and Grey Heron (Ardea cinerea): first insights into the DNA barcodes from Lake Victoria, Tanzania

Most migratory aquatic birds are regarded as reservoir hosts for many parasitic diseases, including digenetic trematodes that cause significant losses to farmed fish. However, in Tanzania, studies of birds focus more on their species diversity and patterns of speciation than their parasites. The current study attempted to use molecular methods, mitochondrial DNA (mtDNA), cytochrome c oxidase subunit I (COX-1) in particular, and ribosomal DNA (rDNA) i.e. 28S rRNA and internal transcribed spacer (ITS1-5.8S-ITS2) regions, to investigate the occurrence of intestinal echinostomatoid species recovered from fish-eating birds, i.e. Grey Herons (Ardea cinerea) and Great Cormorants (Phalacrocorax carbo), from Mwanza Gulf in Lake Victoria. Both morphology and molecular markers revealed the presence of three echinostomatoid species: Stephanoprora amurensis and Petasiger phalacrocoracis in P. carbo, and the Patagifer vioscai in A. cinerea. The present species are reported for the first time in African bird species.

Vocal behaviour of the Great Cormorant Phalacrocorax carbo sinensis during the breeding season

ABSTRACT Capsule Great Cormorants Phalacrocorax carbo sinensis use vocal communication during the breeding season, with males being particularly vocal earlier in the breeding cycle and showing individual variation in some calls, which could be used for individual recognition. Aims To identify and describe vocal behaviour of Great Cormorants, to link calls with observed behaviours and to explore if the calls had potential for individual recognition. Methods We followed 21 nesting pairs of Great Cormorants by videoing and recording their vocal behaviour throughout the breeding season. We linked calls with observed behaviours, and measured the acoustic characteristics of the calls using signal analysis tools in Matlab. Results We identified and measured acoustic characteristics of six different call types: courtship, landing, nest building, nest relief, jumping, and chick begging calls. Five of these call types were linked to distinctive breeding behaviours. Vocal signalling occurred between the male and female, and between parents and offspring. Males showed higher vocal activity than females and used a larger repertoire of calls. The courtship call was the most common call type in both sexes. These calls also differed acoustically between the sexes; male calls were longer in duration than female calls (617 ms versus 323 ms) and had wider bandwidth (763 Hz versus 473 Hz). Conclusion Great Cormorants use vocal communication for social interactions. Males were vocally more active and had a larger repertoire of calls than females, and calls differed between the sexes. Calls of males also differed individually and could, therefore, function for individual recognition in this species.