Bucephala Clangula Research Articles

Pilot study on neonicotinoids in Finnish waterbirds: no detectable concentrations in common goldeneye (Bucephala clangula) plasma

Neonicotinoids have been detected in farmland-associated birds and exposure to these insecticides has been linked to adverse effects. Even though neonicotinoids are mobile and persistent and have been detected in surface waters and aquatic invertebrates, there is a considerable lack of knowledge on their occurrence in waterbirds. Here we investigated the occurrence of seven neonicotinoids and some of their transformation products (imidacloprid, thiacloprid, thiamethoxam, acetamiprid, clothianidin, dinotefuran, nitenpyram, 6-chloronicotinic acid, hydroxy-imidacloprid, imidacloprid-urea, imidacloprid-olefin, thiamethoxam-urea, thiacloprid-amide, acetamiprid-acetate, and acetamiprid-desmethyl) in blood plasma of 51 incubating female common goldeneyes (Bucephala clangula). We collected samples from five different regions from southern to northern Finland encompassing rural and urban settings in coastal and inland areas. Surprisingly, none of the targeted neonicotinoids was found above the limit of detection in any of the samples. As neonicotinoid concentrations in wild birds can be very low, a likely reason for the nil results is that the LODs were too high; this and other possible reasons for the lack of detection of neonicotinoids in the goldeneyes are discussed. Our results suggest that neonicotinoid exposure in their breeding areas is currently not of major concern to female goldeneyes in Finland. Even though this study did not find any immediate danger of neonicotinoids to goldeneyes, further studies including surface water, aquatic invertebrates, and other bird species could elucidate potential indirect food chain effects.

Mass occurrences of Sandeels (Ammodytes spp.) causing aggregations of diving ducks

In autumn 1999, large, compact flocks of foraging diving ducks, particularly Common Eiders Somateria mollissima, were observed within and at the mouth of Trondheimsfjord in Central Norway. Some of these aggregations were at places previously not known as particularly rich feeding grounds. This situation continued through the winter, and still existed in March 2000. Investigations on these feeding grounds showed that the only possible prey species occurring in significant quantities was Sandeel (only Ammodytes tobianus was verified). Although most of the fish were swallowed before the birds reached the surface, some ducks (including Velvet Scoter Melanitta fusca and Goldeneye Bucephala clangula) were observed eating Sandeels. Sandeel populations fluctuate in size annually and shoals are very patchily distributed. Consequently, the very variable occurrence in time and space of this food resource may occasionally bring about unusually dense and patchy aggregations of various species of diving ducks. Due to the specific habitat requirements of the Sandeel, these aggregations may also occur at localities that are not generally preferred feeding grounds for diving ducks, as was the case here. These findings may be relevant for some monitoring projects involving populations of diving ducks in marine environments.

Body mass changes of dabbling and diving ducks wintering in California

AbstractBird body mass is often used as an index of body condition and fluctuates throughout the year in response to environmental conditions and avian life‐history events. We examined the body mass of 59,572 ducks representing 13 species (7 dabbling duck species and 6 diving duck species) harvested within the 3 regions of the Central Valley in California, USA (Sacramento Valley, Suisun Marsh, San Joaquin Valley). Data collection occurred in winter during 5 hunting seasons (2014–2015, 2015–2016, 2017–2018, 2018–2019, 2019–2020). For all species, age, and sex classes, the body mass of dabbling ducks varied temporally and was lowest at the end of the hunting season in late January, declining from the beginning of the hunting season in mid‐October (northern pintail [Anas acuta]: −11.4% to −20.4%; northern shoveler [Spatula clypeata]: −3.5% to −17.3%; cinnamon teal [Anas cyanoptera]: −5.0% to −17.1%; American wigeon [Mareca americana]: −6.9% to −12.2%; American green‐winged teal [Anas carolinensis]: −5.9% to −11.9%; mallard [Anas platyrhynchos]: −1.8% to −9.6%; gadwall [Mareca strepera]: −2.2% to −8.4%). As expected, adults (after hatch‐year) were heavier than immature (hatch‐year) birds (within males: 0.6–8.6%; within females: 0.1–6.6%) and males were heavier than females (within adults: 3.1–38.6%; within immatures: 5.4–33.5%) at the end of the hunting season in all species. Within dabbling duck species, body masses did not differ among regions at the beginning of the hunting season but were heavier in the Sacramento Valley (0.5–14.4%) than other areas by the end of the hunting season. In contrast, body masses of diving ducks did not vary substantially during the hunting season or among regions. Diving ducks demonstrated inconsistent changes in mass from the beginning to the end of the season (lesser scaup [Aythya affinis]: 3.4% to 12.3%; canvasback [Aythya valisineria]: 5.1% to 6.1%; bufflehead [Bucephala albeola]: −3.2% to 1.6%; ring‐necked duck [Aythya collaris]: −4.9% to 2.6%; common goldeneye [Bucephala clangula]: −3.2% to −2.4%; ruddy duck [Oxyura jamaicensis]: −16.5% to 5.5%). The substantial temporal and spatial differences in dabbling duck body masses suggest that habitat quality (as measured by caloric value of the available food) or quantity may decline during winter and varies regionally within California's Central Valley.

Ecological correlates of alternative reproductive tactics: conspecific brood parasitism rates vary with nest predation and seasonal effects influenced by climate change

Ecological and social factors shape individual reproductive strategies. Climate change has wide‐ranging effects on the timing of reproduction and availability of nesting sites for many birds. Ecological factors such as season length or predation rate could in turn affect the relative success rates of alternative reproductive tactics (ARTs). A new article by Pöysä (2024) featuring a long‐term study of common goldeneyes Bucephala clangula highlights the role of climate change in altering rates of conspecific brood parasitism (CBP) by affecting nest initiation dates and season length. While some authors have emphasized the effects of spatial and temporal aggregation of nests in promoting tactics of reproductive interference, few studies have addressed the effects of environmental variables on rates of CBP and other ARTs. I review some of the evidence for a relationship between population‐level nest predation rate and rates of CBP, principally in ducks and rails, and suggest a role for high rates of nest loss from all sources in the evolution of CBP and host responses. There is a need for further studies that examine environmental correlates of ARTs. Long‐term studies have the highest potential to reveal how shifts in phenology and life history variables may respond to environmental perturbations. Comparative studies of similar species in remote geographic locations can add perspective of how different ecological variables affect the prevalence of ARTs.

Features of the anatomy of the right half of the heart in the common Gogol (Bucephala clangula)

The common goldeneye (Bucephala clangula) is a sea duck that belongs to the order Anseriformes and the family Anatidae. Due to their lifestyle, they are able to hold their breath for up to 30 minutes and dive to a depth of 10 meters. Such a load on the duck’s body contributes not only to the restructuring of morphological structures, but also to increased heart function. An analysis of the sources showed that the morphology of the heart in mammals and birds has been studied, but no work on the morphology of the right half of the heart in the common goldeneye was found, which was the purpose of our study. The material was hearts from male common goldeneye – 1.5-2 years old (n=3), caught in the bay of the Angara River. Thus, the cardiac index in the common goldeneye was determined to be 83%, and the presence of epicardial fat was noted on the side of the coronary and paroconal sulcus. The right ventricle is located above the level of the apex of the left ventricle, and 70.7% surrounds the borders of the left ventricle. The free appendages of the atrium are formed with the participation of eight pectineal muscles, which in the form of a ridge begin from the muscular valve, and dorsomedially closer to the atrial sinus, become thinner and unite at one point. The length of the pectineal muscle’s ranges at 8.2±0.54 mm, thickness 0.83±0.02 mm. The right ventricle is separated from the atrium by a muscular valve, which has its own characteristics of fastening, where its high part extends from the level of the subsinus groove (interventricular septum), forms the parietal part of the atrioventricular orifice and at the level of the vascular cone narrows slightly and is fixed in two parts to the wall of the ventricle. On the side of the right ventricle, trabeculae are expressed only under the muscular valve, where the crossbars are directed from left to right and downward, from its narrowing. The crossbars are 6.9±0.23 long and 0.83±0.03 mm wide, with jumpers up to 1 mm.

Nest predation and climate change as drivers of alternative reproductive tactics in a migratory species

Alternative reproductive tactics enable individuals to choose a reproductive tactic relative to their status and prevailing environmental conditions in a way that increases their fitness. For example, females in many avian species show phenotypic plasticity and employ alternative reproductive tactics to cope with changes in predation risk and climate. Conspecific brood parasitism (CBP), in which females lay eggs in nests of conspecifics, is one example of such behaviour. It has been proposed that when prospects for successful nesting are low and/or costs of reproduction are high, females employ tactics of low effort such as non‐breeding and parasitic laying. When environmental conditions are ideal and prospects for success high, females can increase their reproductive effort above typical nesting by laying parasitic eggs prior to initiating their own nest. Here, I used this flexible life‐history strategy concept and long‐term (1994‒2022) population level data of the common goldeneye Bucephala clangula to study how the rate of parasitic laying varies in relation to variation in nest predation risk and in the timing and length of the breeding season, the latter being measured by the timing of ice breakup. Nest predation rate in the previous year and timing of ice breakup interactively affected parasitic laying, the rate of parasitic laying being particularly high in years with late ice breakup and high nest predation rate in the previous year. Furthermore, the proportion of predated eggs was lower in parasitized nests than in non‐parasitized nests, while the opposite was true for the proportion of eggs that failed in other way. As a consequence, the final number of young produced per nest was higher for parasitized nests. The findings of this study show that changes in environmental conditions affect the dynamics of alternative reproductive tactics in goldeneyes, with consequences to population level reproductive output.

Changes in the adult sex ratio of six duck species breeding populations over two decades

Despite all efforts, long-term changes in the adult sex ratios of breeding duck populations are still unclear; this uncertainty is especially true for male-bias populations, which are often under the scrutiny of researchers lacking convenient results for the active protection of endangered species. Species with male-bias populations are usually strongly affected by a decline in population size that leads to a higher extinction risk. In this study, we examined our long-term data of the abundance of breeding populations in six duck species (Mallard Anas platyrhynchos, Gadwall Mareca strepera, Red-crested Pochard Netta rufina, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, and Common Goldeneye Bucephala clangula) from fishponds in South Bohemia, Czechia, between 2004 and 2022. This evidence was used to assess long-term changes in the adult sex ratio in these breeding populations and investigate the possible effects of the NAO index (North Atlantic Oscillation index) on them, indicating climate conditions in winter. We determined a long-term decrease of the proportion of females in the breeding season in two of the six examined species: Common Pochard and Red-crested Pochard, which is driven by the long-term increase in the number of males in contrast to the decreasing or stable number of females likely caused by different migration behaviours between females and males. In the case of Common Pochard, in breeding populations, we estimated 60–65% of males in the early 2000s rising to 75–80% in the early 2020s. However, we establish no significant effects linked to climate conditions of the previous winter in these species as a crucial cause of the changes of the proportion of females in the breeding population.

Winter avifauna habitat types of urban agglomerations: comparison by qualitative and quantitative indicators

Background. The winter avifauna of urban agglomerations is a rather dynamic object of research, whose indicators differ across cities and years of observation. Depending on the species characteristics and the level of anthropogenization, birds in the territory of cities choose different types of habitats, which also requires analysis. Materials and Methods. Research on the species composition of wintering birds on the territories of Zhydachiv and Lviv urban agglomerations was carried out in winter periods of 2020–2023 by means of field trips using the method of point records (Bibby et al., 2000). In order to count small species of Passeriformes accurately, a slightly modified version of this method was used. In this case, observations were carried out in a double radius. Birds were recorded separately in R1 – up to 25 m and R2 – from 25 to 50 m. The optimal time for counting at one point is 8–10 minutes. The counting area corresponds to a circle with a known radius. Research was carried out mainly in morning hours – from 8:00 to 11:00 in the case of absence of heavy precipitation, fog or strong wind. Results and Discussion. After comparing the winter avifauna of urban agglo­merations of the regional (Lviv) and district (Zhydachiv) levels, which differ in the level of environmental transformation, we established certain differences. A total of 48 species of wintering birds have been recorded, of which the Сommon Goldeneye (Bucephala clangula) and the Ural Owl (Strix uralensis) are protected by the Red Data Book of Ukraine. Conclusion. For each of the agglomerations, dominant species of birds have been determined. Admittedly, birds in the territory of cities seek to occupy a territory with conditions most similar to the natural environment. Additionally, we attempted to understand the patterns of distribution of wintering species in the study area and the reasons for such placement.

Pine marten predation of common goldeneye nests: Effects of cavity age and habitat override any effect of microtine rodent abundance.

According to the alternative prey hypothesis (APH), the temporal synchrony in population fluctuations of microtine rodents and other small herbivores in boreal areas is caused by generalist predators with numerical and functional response to microtines, leading to an increased predation of prey alternative to microtines in the low phase of the microtine population fluctuations. The tree-climbing pine marten (Martes martes) is a food generalist that includes bird eggs among its alternative prey, also eggs of the cavity-nesting common goldeneye (Bucephala clangula). We used long-term data to test whether pine marten predation of goldeneye eggs in nest boxes varied as predicted by the APH. As a measure of microtine abundance at the time of nesting, we applied two measures. First, for goldeneye nests located <40 km from our microtine trapping site, we applied the trapping index of microtine rodents. Second, to also use data from nests located >40 km from our microtine trapping site, and from nests in years when trapping was not conducted, we used two proxies for the microtine abundance: whether boreal owls (Aegolius funereus) nested in any of our boxes <40 km from each goldeneye nest and the average clutch size of these boreal owls. The probability of predation of a goldeneye nest was independent of the microtine trapping index and independent of the proxies for microtine abundance. However, it increased with cavity age, taken as the number of nesting seasons elapsed since the actual nest box was installed, and declined with distance from habitat with forest canopy. The effect of cavity age confirms that the long-term spatial memory of pine marten is an important factor in the pattern of its predation on nests in tree cavities.

Indicator species reveal the physical and biological singularity of esker ecosystems

Eskers are complex geological formations shaped with a linear accumulation of sand and gravel under the glaciers during the last ice age and that provide crucial resources such as drinking water, sand/gravel, outdoor recreational sites, and productive forests. Surrounding sand and gravel and connection with the groundwater influences the physicochemical properties of lakes on esker which can benefit different biotic communities in the food web. The sustainable management of resources provided by eskers requires baseline ecological knowledge of these ecosystems. However, very little information exists about the ecology of freshwater ecosystems on eskers. This study uses a food web approach to identify the environmental variables, biological diversity, and indicator species associated with esker lakes to better understand their ecological functioning and biodiversity patterns to benefit their sustainable management and conservation. Fifty lakes were sampled in the Abitibi-Témiscamingue region (Canada), half on eskers and half on the surrounding boreal clay belt to include the most abundant lake ecosystems of the region. Physicochemical, environmental, and anthropogenic variables measured in the two lake types showed that esker lakes differed markedly from clay lakes. Nutrient concentrations, conductivity, and macrophyte cover were significantly lower in esker lakes than in clay lakes, whereas dissolved oxygen saturation and concentration showed the opposite trend. Three interconnected trophic levels of the esker lake food webs—waterbird, fish, and macroinvertebrate communities—were characterized for biological diversity and the associated species. We found a significantly lower Shannon diversity index for waterbirds (mean ± standard deviation; 0.7 ± 0.2), fish (0.4 ± 0.3), and a tendency for a lower value for macroinvertebrates (0.9 ± 0.3) in esker lakes than the clay lakes (1.1 ± 0.4, 0.9 ± 0.3, and 1.3 ± 0.5, respectively). Common goldeneye (Bucephala clangula) and Canada goose (Bucephala clangula) were associated significantly with esker lakes and identified as indicator species for esker lakes. In contrast, ring-necked duck (Aythya collaris) and hooded merganser (Lophodytes cucullatus) were associated significantly with clay lakes. Perlidae was similarly associated with esker lakes as an indicator for macroinvertebrates. Anthropogenic activities such as forest harvesting have altered the waterbird community, and recreational activities around the lakes have modified the fish and macroinvertebrate communities. We conclude that esker lakes differ from other regional lakes and are associated with specific environmental and biological variables and indicator species. The biological diversity in esker lakes is lower than that of clay lakes for all studied trophic levels of the food web, but these waterbodies provide preferential habitats for some species. This research provides the first baseline ecological information necessary to establish sustainable management and conservation strategies for this vulnerable ecosystem.

Cold wintering of coastal birds in the source and upper reaches of the Angara river: Changes in abundance and species structure in the conditions of a sharp climate warming

Based on long-term research (1972-2023) and analysis of literature data, materials on the dynamics of the number and species structure of wintering shorebirds and waterfowl on cold wintering in the source and upper reaches of the Angara River (up to the town of Usolye-Sibirskoye) are presented. This is the largest cold wintering of coastal birds in Eastern Siberia – up to 55.0-60.0 thousand birds, the formation of which is due to very specific conditions of the upper reaches of the Angara River. This is the thermal refugium of the Upper Angara region, which ensures the accumulation of birds at the end of migration in more favorable areas of this region. It is divided into two sections: the first stretches from the source of the Angara River to the village of Taltsy, the second from the Irkutsk hydroelectric dam to the town of Usolye-Sibirskoye, and in warm winters slightly below it. On the basis of special works on the study of the dynamics of the number and species structure of birds, special methods have been developed: accounting on ice holes, accounting during the evening flight of birds to the lake Baikal (during cold periods) and accounting using a hovercraft (SVP) (during periods of severe climate warming). The basis of wintering birds is the Goldeneye Bucephala clangula (from 95.0% to 98.5% of their total species structure). However, the structure of secondary species can increase dramatically and we have noted new species that have never been found here before. The collected materials allow us to understand the reasons that determine the dynamics of the number and species structure of coastal birds in the “cold” wintering grounds of Inner Asia in the conditions of a sharp warming of the climate

The impact of climate sensitive factors on the exposure to organohalogenated contaminants in an aquatic bird exploiting both marine and freshwater habitats

To assess how climate-sensitive factors may affect the exposure to organochlorines (OCs) and perfluoroalkyl substances (PFASs), we monitored concentrations in eggs of the common goldeneye (Bucephala clangula) over two decades (1999–2019) in central Norway. The goldeneye alternates between marine and freshwater habitats and is sensitive to climate variation, especially due to alterations in ice conditions which may affect feeding conditions. We assessed how biological factors such as diet (stable isotopes δ13C and δ15N), the onset of egg laying, and physical characteristics such as winter climate (North Atlantic Oscillation: NAOw) influenced exposure. We predicted compounds to show different temporal trends depending on whether they were still in production (i.e. some PFASs) or have been banned (i.e. legacy OCs and some PFASs). Therefore, we controlled for potential temporal trends in all analyses. There were declining trends for α- and γ-hexachlorocyclohexane (HCH), oxychlordane, cis-chlordane, cis-nonachlor, p,p′-dichlorodiphenyltrichloroethane (p.p′-DDT) and less persistent polychlorinated biphenyl (PCB) congeners (e.g. PCB101). In contrast, the dominant compounds, such as p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) and persistent PCB congeners, were stable, whereas hexachlorobenzene (HCB) increased over time. Most OCs were positively related to δ15N, suggesting higher exposure in birds feeding at upper trophic levels. Chlordanes and HCB were positively associated with δ13C, indicating traces of marine input for these compounds, whereas the relationships to most PCBs were negative. Among PFASs, perfluorooctanesulfonamide (PFOSA) and perfluorohexane sulfonic acid (PFHxS) declined. Most PFASs were positively associated with δ13C, whereas there were no associations with δ15N. Egg laying date was positively associated to perfluoroheptanesulfonic acid (PFHpS), perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), suggesting that some of the PFAS load originated from the wintering locations. Although NAOw had little impact on the exposure to organohalogenated contaminants, factors sensitive to climate change, especially diet, were associated with the exposure to OHCs in goldeneyes.

Ecosystem specific accumulation of organohalogenated compounds: A comparison between adjacent freshwater and terrestrial avian predators

Insight into processes determining the exposure of organohalogenated contaminants (OHCs) in wildlife might be gained from comparing predators in different ecosystems. This study compared two avian predator species with similar food chain lengths: the goldeneye duck (Bucephala clangula) and the tawny owl (Strix aluco) breeding in adjacent freshwater- and terrestrial ecosystems in central Norway. We measured lipophilic organochlorines (OCs) and protein-bound perfluorinated substances (PFASs) in eggs of the two species over 21 years (1999–2019). Across years, the proportional distribution of OCs (∼90% of the ΣOHC load) relative to PFASs (∼10%) was similar in the two species. Moreover, ΣOC concentrations were similar between the species, but PFAS compounds were 2–12 times higher in the goldeneyes than in tawny owls. OC-pesticides dominated in tawny owls (∼60% of ΣOC), whereas persistent polychlorinated biphenyl (PCBs) congeners were the main OC components in goldeneyes (∼70% of ΣOC). The lipid-normalized concentrations of most OC-pesticides and the less persistent PCB101 declined significantly in both species. Hexachlorobenzene (HCB), p,p’-dichlorodiphenyldichloroethylene (p,p’-DDE), and more persistent PCBs decreased in tawny owls, while they tended to increase in goldeneyes. The increase in HCB was particulary robust. Among the PFASs, contrasted temporal trends were found across the species for four out of 11 compounds: PFOS declined while most perfluorocarboxylic acids (PFCAs) increased in tawny owls. In contrast, most PFASs were stable in goldeneyes. Moreover, there was no annual covariance between the OHC exposure in the two species: i.e., high concentrations in one species in a given year did not translate into high concentrations in the other. Hence, the two avian predators in adjacent ecosystems seem to be subject to different processes determining the OHC exposure, probably related to variation in diet and climate, long-range transport of different contaminants, and emissions of pollution locally.

Temporal changes in species richness of waterfowl (Anseriformes) community in D’Ering Memorial Wildlife Sanctuary, Arunachal Pradesh, India

We conducted five yearly field surveys to assess long-term changes in the species richness, abundance, and composition of waterfowl populations (Anseriformes) in the D’Ering Memorial Wildlife Sanctuary, a significant staging area on migratory flyways with one of the largest concentrations of waterfowl in Arunachal Pradesh, especially during winter. A total of 8,040 birds belonging to 17 species of Anatidae were recorded, including two threatened species. The most abundant species were Tadorna ferruginea, Anas poecilirhnycha, and Bucephala clangula, with relative abundances of 29%, 10%, and 9.4%, respectively. Species richness was highest in winter (H’= 2.40; January H’= 2.43) and lowest in the monsoon (H’= 1.48; August, H’= 1.12). Seasonal difference in species richness was noticed for winter visitors, but not for year-round residents. We observed a major declining trend for seven species. Findings from this study can be used for further ecological assessment of the waterfowl community of the sanctuary.

ВЕСНЯНІ МІГРАЦІЙНІ СКУПЧЕННЯ ВОДОПЛАВНИХ І НАВКОЛОВОДНИХ ПТАХІВ У ЦЕНТРАЛЬНІЙ ЧАСТИНІ КРЕМЕНЧУЦЬКОГО ВОДОСХОВИЩАВ 2014-2016 РР

Introduction. Kremenchuk reservoir plays an important role for waterbirds and wetland birds during seasonal migrations. Therefore, we provide the monitoring of the avifauna during seasonal migrations in the central part of the reservoir. The article details the results of the wetland birds and waterbirds censuses in the spring periods of 2014-2016.Purpose. To assess the species composition of wetland birds and waterbirds, their relative numbers, and seasonal dynamics in the spring period in the central part of the Kremenchuk reservoir. To compare the results with those obtained during 2007-2013.Methods. Bird censuses were conducted along the dam through the Kremenchuk Reservoir. Used the route-point method of censuses. In total 17 bird censuses were conducted (5-6 each year).Results. During the period of studies, 36 species of waterbirds and wetland birds were detected. The most numerous migratory species were Anser albifrons, Anas plathyrhynchos, A. penelope, Aythya fuligula, and Larus cachinans. Another 7 species can be considered common (Phalacrocorax carbo, Cygnus olor, Anser fabalis, Bucephala clangula, Fulica atra, Larus ridibundus, and L. canus). Five identified species are listed in the Red Data Book of Ukraine (Cygnus bewickii, Anas strepera, Bucephala clangula, Haliaeetus albicilla, and Haematopus ostralegus). The highest number of birds was observed in the second and third decades of March.Originality. Our data supplement the information on the species composition of wetland and waterbirds, their number, and dynamics in the central part of the Kremenchuk reservoir in the spring. The greatest impact on the number of birds at the local level have temperature, the area of ice cover, the water level in the reservoir.Conclusions. The central part of the Kremenchuk reservoir plays an important role for migratory waterbirds and wetland birds. A significant number of these birds (from 5 to more than 20 thousand) use this area for rest and feeding during the period of the spring migration. The most important for these birds part of the studied area is the water area of the Ornithological Reserve "Lypivskiy".Key words: migration, number, migration waves, phenology.

Local variation in the timing and advancement of lake ice breakup and impacts on settling dynamics in a migratory waterbird

Timing of ice-out is important to fundamental hydrological and ecological processes in freshwater ecosystems at high northern latitudes. While earlier ice-out in lakes during the last century is a well-documented phenomenon across the Northern Hemisphere, local variation in the rate of advancement of ice-out has received little attention. Here, records of ice-out date in 1991–2020 from 37 small lakes in a boreal catchment area in southeastern Finland were used to study variation in the timing of ice-out and its advancement. In addition, data of settling phenology of migratory common goldeneyes (Bucephala clangula) at the study lakes were used to examine how between-year and within-season variation in the timing of ice-out affects lake settlement of the species. Overall, ice-out date (IOD, the timing of ice break-up in the spring) advanced 9.8 days during the 30-year study period, April temperature being more important than winter temperature (severity) in determining the IOD. Rate of the advancement of IOD in individual lakes varied from 1.5 to 16.1 days, having advanced more in relatively larger lakes. Lakes at higher elevations had later mean IOD than lakes at lower elevations. Within-season differences among the lakes in IOD increased from 1991 to 2020, this variation being mainly driven by temperature during the ice melting period. Lakes with late mean IOD were settled later in a season by breeding common goldeneyes than lakes with early IOD. The faster the ice melting progressed within a season, the faster common goldeneyes settled the breeding lakes. The results demonstrate how global warming differently affects IOD in boreal lakes even within the same catchment area. More research in the landscape context is needed to enhance our understanding of changes in IOD in boreal lakes and how differently advancing IOD affects local dynamics of species dependent on open water.

Behavioural responses of non-breeding waterbirds to marine traffic in the near-shore environment

ABSTRACT Capsule Recording of behavioural responses to ferry traffic for 11 target species showed that Red-throated Diver Gavia stellata, Slavonian Grebe Podiceps auratus, and Black-throated Diver Gavia arctica were most likely to react to passing vessels. Aim To provide information on how responses to marine traffic vary between waterbird species to inform marine spatial planning and environmental impact assessments in the near-shore environment. Methods We recorded behavioural responses to ferry traffic for 11 target species in near-shore waters: Common Eider Somateria mollissima, Goldeneye Bucephala clangula, Long-tailed Duck Clangula hyemalis, Velvet Scoter Melanitta fusca, Red-breasted Merganser Mergus serrator, Black-throated Diver, Great Northern Diver Gavia immer, Red-throated Diver, European Shag Gulosus aristotelis, Slavonian Grebe and Black Guillemot Cepphus grylle. Responses were analysed using generalized linear models and mixed models. Results Red-throated Diver, Black-throated Diver and Slavonian Grebe were the most likely species to exhibit a response to passing vessels. While Red-throated Divers and Slavonian Grebes were highly likely to flush, Black-throated Divers and Great Northern Divers rarely took flight, instead favouring swim or dive responses. In rougher sea conditions birds were more likely to take flight, and the propensity to respond declined across the wintering period. Conclusions This research provides comparative evidence on the behavioural responses of waterbirds to marine traffic. The results support previous studies which highlighted the high sensitivity of diver species to disturbance and provide new evidence that Slavonian Grebe may also be a high sensitivity species.

Nest box reuse in a migrating bird is independent of nest content

Site fidelity after successful nesting is an adaptation to spatially heterogeneous and temporally auto-correlated risk of nest predation. Cavity-nesting common goldeneye (Bucephala clangula) females use this strategy to minimize nest predation from pine marten (Martes martes), but because goldeneyes migrate they may save time when deciding where to nest by relying on information about successful nests gained in the previous year. I tested whether reuse of a nest box where the previous nest was successful is affected by the content. After a goldeneye had successfully nested, I manipulated nest box availability by offering two nest boxes; one in the original nest tree and one in a new tree for the season, each containing either old nest material from the successful nest or new nest material, i.e. wood shavings. The boxes were installed and relocated when goldeneyes were absent from the study area. The manipulation was designed to test whether goldeneyes reuse a cavity based on information conveyed by its current content, or on private or public information gained in the previous nesting season. Goldeneyes consistently reused the box in the original nest tree, independent of box content. Thus, when the information available in the current nesting season conflicted with information acquired in the previous nesting season, the goldeneyes relied on the latter rather than on information that would cost valuable time to update after arrival in spring. The common practice among ornithologists and land managers to clean nest boxes after each nesting would not affect cavity reuse in the goldeneye.

Eneolithic pile dwellers captured waterfowl in winter: Analysis of avian bone remains from two pile dwellings in Ljubljansko barje (Slovenia)

AbstractThis study presents the results of an ornitho‐archaeological analysis of avian bones from Stare gmajne and Blatna Brezovica, two Eneolithic pile dwelling sites in the area of Ljubljansko barje, Slovenia. Avian bone remains, together with remnants of huts, tools, mammal bones and bones of other vertebrates, represent the material remnant of a pile dwelling culture from the second half of the fourth millennium BC.A total of 2091 avian bones or fragments thereof were excavated. The avifauna includes 682 taxonomically identified remains (NISP), assigned to 15 bird taxa. Taxonomically, species from the Anatidae group predominate (68.7% of NISP), mainlyBucephala clangula(40.3% of NISP). Also abundant isFulica atra(26.2% NISP) from the family Rallidae. In the ecological context, species inhabiting aquatic or marshy habitats prevail. Representatives of three ecomorphological groups of waterbirds were found: diving birds (Podicepssp.,Phalacrocorax carbo,Aythya fuligula,B. clangulaandMergussp.), waterbirds (Cygnussp.,Ansersp.,Anassp. andF. atra) and the marsh species group (Ardea cinerea).The absence of medullary bone and the abundance of wintering species in the area are consistent with the hypothesis that the birds were captured during the winter season. Taphonomic evidence (burned bones) suggests that the studied assemblages were human food waste. The abundance of avian bone remains supports the hypothesis that the native peoples were skilled hunters of aquatic birds.

Changes in numbers and distribution of wintering waterbirds around Gotland 1969–2020

The coastal areas of the island of Gotland in the center of the Baltic Sea is an important wintering site for waterbirds in Sweden. Gotland offers extensive areas of shallow feeding grounds and, due to its location, some open waters remain available even during harsh winters. Wintering waterbirds have been counted annually on the island since the start of the International Waterbird Census in 1967, with full coverage of all the inshore areas around the main island obtained during the years 1969–1978 and 2013–2020. Between these two periods, the mean total number of wintering waterbirds increased from 32,000 to 111,500. The most numerous species were Mallard Anas platyrhynchos, Tufted Duck Aythya fuligula, and Common Goldeneye Bucephala clangula. Some species such as Eurasian Wigeon Mareca penelope, Eurasian Teal Anas crecca, and Gadwall Mareca strepera started to winter during the second period. Marked increases were also found for Smew Mergellus albellus and Greater Scaup Aythya marila, likely related to progressively milder winters in recent years.