Energetic trade-offs in migration decision-making, reproductive effort and subsequent parental care in a long-distance migratory bird.

Migratory species trade-off long-distance movement with survival and reproduction, but the spatio-temporal scales at which these decisions occur are relatively unknown. Technological and statistical advances allow fine-scale study of animal decision-making, improving our understanding of possible causes and therefore conservation management. We quantified effects of reproductive preparation during spring migration on subsequent breeding outcomes, breeding outcomes on autumn migration characteristics and autumn migration characteristics on subsequent parental survival in Greenland white-fronted geese (Anser albifrons flavirostris). These are long-distance migratory birds with an approximately 50% population decline from 1999 to 2022. We deployed GPS-acceleration devices on adult females to quantify up to 5 years of individual decision-making throughout the annual cycle. Weather and habitat-use affected time spent feeding and overall dynamic body acceleration (i.e. energy expenditure) during spring and autumn. Geese that expended less energy and fed longer during spring were more likely to successfully reproduce. Geese with offspring expended more energy and fed for less time during autumn, potentially representing adverse fitness consequences of breeding. These behavioural comparisons among Greenland white-fronted geese improve our understanding of fitness trade-offs underlying abundance. We provide a reproducible framework for full annual cycle modelling using location and behaviour data, applicable to similarly studied migratory animals.

Time-varying effects of local weather on behavior and probability of breeding deferral in two Arctic-nesting goose populations.

Arctic-nesting geese face energetic challenges during spring migration, including ecological barriers and weather conditions (e.g., precipitation and temperature), which in long-lived species can lead to a trade-off to defer reproduction in favor of greater survival. We used GPS location and acceleration data collected from 35 greater white-fronted geese of the North American midcontinent and Greenland populations at spring migration stopovers, and novel applications of Bayesian dynamic linear models to test daily effects of minimum temperature and precipitation on energy expenditure (i.e., overall dynamic body acceleration, ODBA) and proportion of time spent feeding (PTF), then examined the daily and additive importance of ODBA and PTF on probability of breeding deferral using stochastic antecedent models. We expected distinct responses in behavior and probability of breeding deferral between and within populations due to differences in stopover area availability. Time-varying coefficients of weather conditions were variable between ODBA and PTF, and often did not show consistent patterns among birds, indicating plasticity in how individuals respond to conditions. An increase in antecedent ODBA was associated with a slightly increased probability of deferral in midcontinent geese but not Greenland geese. Probability of deferral decreased with increased PTF in both populations. We did not detect any differentially important time periods. These results suggest either that movements and behavior throughout spring migration do not explain breeding deferral or that ecological linkages between bird decisions during spring and subsequent breeding deferral were different between populations and across migration but occurred at different time scales than those we examined.

Annual variation in waterbird clutch initiation date in relation to spring thaw in Arctic Russia.

To test for the degree of species-specific variation in clutch initiation date in relation to spring thaw, we recorded first egg dates in 1433 nests of seven large bodied long-distance migratory waterbird species breeding on Ayopechan Island in the Chaun Delta, Chukotka, in the Russian Arctic during 2002-2020. Pacific Loon Gavia pacifica, Sandhill Crane Grus canadensis and Glaucous Gull Larus hyperboreus all adjusted timing of clutch initiation completely to annual variation in first frost-free dates. First egg dates of Spectacled Eider Somateria fischeri also significantly advanced in warmer springs, but the rate of change was significantly less than unity, implying a reduced capacity to accommodate change in vernal thaw that may not be able to keep up with greater change in the future. Long-tailed Duck Clangula hyemalis and Vega Gull Larus vegae showed a tendency for earlier first egg dates in years with earlier first frost-free date, but for both species, the relationship failed to reach statistical significance. Bewick's Swan Cygnus columbianus showed almost no change in mean first egg date across the observed variation in first frost-free dates. Based on these data, we suggest that while all seven species showed signs of plasticity in their timing of onset of breeding, Pacific Loon, Sandhill Crane and Glaucous Gull showed greater adaptability to adjust the timing of their breeding season to recent variation in spring thaw than the other four species studied here over this period.

Changes in flight paths of large-bodied birds after construction of large terrestrial wind turbines.

The proliferation of ever-larger wind turbines poses risks to wildlife, especially from avian collision, yet avoidance behaviour of large-bodied, long-lived bird species in relation to wind turbines remains little studied away from collision "black spots" and offshore marine environments. Here, three-dimensional flight trajectory data are reported from a laser range-finder study of local movements of large-bodied birds (e.g. swans, geese, gulls, cormorants, raptors and cranes, whose populations are relatively more demographically sensitive to collision mortality) in relation to seven terrestrial 150-222 m high (mean 182 m) wind turbines constructed in Denmark in a N-S line. Comparisons of two-dimensional flight passages between turbines pre- (n = 287) and post-construction (n = 1210) showed significant (P < 0.0001) reductions from 48% to 35% within 150 m of each turbine, with corresponding increase 200-300 m from turbines. Results also showed a significant (P < 0.001) 50% reduction in the percentage of avian passages (from 21% to 10%) through the maximum turbine sweep area after construction and that the proportion of birds that passed between turbines at heights below (0-45 m) and above the turbine sweep area (> 182 m) were significantly greater (P < 0.0001) post-construction than prior to construction. These are the first results from tracking large-bodied bird flight trajectories to show the magnitude of their vertical and horizontal adjustments to the presence of turbines, which have implications for assumptions of even flight densities made by collision risk models currently used to predict avian turbine collision rates.

Long-term declines of European insectivorous bird populations and potential causes.

Evidence of declines in insect populations has recently received considerable scientific and societal attention. However, the lack of long-term insect monitoring makes it difficult to assess whether declines are geographically widespread. By contrast, bird populations are well monitored and often used as indicators of environmental change. We compared the population trends of European insectivorous birds with those of other birds to assess whether patterns in bird population trends were consistent with declines of insects. We further examined whether declines were evident for insectivores with different habitats, foraging strata, and other ecological preferences. Bird population trends were estimated for Europe (1990-2015) and Denmark (1990-2016). On average, insectivores declined over the study period (13% across Europe and 28% in Denmark), whereas omnivores had stable populations. Seedeaters also declined (28% across Europe; 34% in Denmark), but this assessment was based on fewer species than for other groups. The effects of insectivory were stronger for farmland species (especially grassland species), for ground feeders, and for cold-adapted species. Insectivory was associated with long-distance migration, which was also linked to population declines. However, many insectivores had stable populations, especially habitat generalists. Our findings suggest that the decline of insectivores is primarily associated with agricultural intensification and loss of grassland habitat. The loss of both seed and insect specialists indicates an overall trend toward bird communities dominated by diet generalists.

Declinaciones a Largo Plazo de Poblaciones de Aves Insectívoras en Europa y las Causas Probables Resumen La evidencia de las declinaciones poblacionales de insectos ha recibido recientemente una atención considerable por parte de la comunidad científica y la sociedad. Sin embargo, la falta de un monitoreo prolongado de los insectos complica valorar si estas declinaciones tienen una distribución extensa geográficamente. Como contraste, las poblaciones de aves tienen un monitoreo constante y con frecuencia se usan como indicadores del cambio climático. Comparamos las tendencias poblacionales de las aves insectívoras de Europa con las de otras aves para valorar si los patrones en las tendencias poblacionales de aves son consistentes con las declinaciones de insectos. Además examinamos si las declinaciones eran evidentes para aves insectívoras con diferentes hábitats, estratos de alimentación, y otras preferencias ecológicas. Las tendencias poblacionales de las aves se estimaron para Europa (1990 - 2015) y para Dinamarca (1990 - 2016). En promedio, las aves insectívoras declinaron a lo largo del periodo de estudio (13% en Europa y 28% en Dinamarca) mientras que las aves omnívoras tuvieron poblaciones estables. Las poblaciones de aves que se alimentan de semillas también declinaron (28% en Europa; 34% en Dinamarca), pero esta valoración se basó en menos especies que para los otros grupos. Los efectos de la insectivoría fueron más evidentes para las especies de tierras agrícolas (especialmente las especies de pastizales), para las especies que se alimentan sobre el suelo y para las especies adaptadas al frío. La insectivoría estuvo asociada con la migración de larga distancia, la cual también estuvo ligada a las declinaciones poblacionales. Sin embargo, muchas aves insectívoras tuvieron poblaciones estables, especialmente aquellas generalistas de hábitat. Nuestros hallazgos sugieren que la declinación de las aves insectívoras está asociada principalmente con la intensificación agrícola y la pérdida de pastizales. La pérdida de aves cuya alimentación es especialista en insectos o en semillas indica una tendencia general hacia comunidades de aves dominadas por aquellas con dietas generalistas.

Making do with less: must sparse data preclude informed harvest strategies for European waterbirds?

The demography of many European waterbirds is not well understood because most countries have conducted little monitoring and assessment, and coordination among countries on waterbird management has little precedent. Yet intergovernmental treaties now mandate the use of sustainable, adaptive harvest strategies, whose development is challenged by a paucity of demographic information. In this study, we explore how a combination of allometric relationships, fragmentary monitoring and research information, and expert judgment can be used to estimate the parameters of a theta-logistic population model, which in turn can be used in a Markov decision process to derive optimal harvesting strategies. We show how to account for considerable parametric uncertainty, as well as for different management objectives. We illustrate our methodology with a poorly understood population of Taiga Bean Geese (Anser fabalis fabalis), which is a popular game bird in Fennoscandia. Our results for Taiga Bean Geese suggest that they may have demographic rates similar to other, well-studied species of geese, and our model-based predictions of population size are consistent with the limited monitoring information available. Importantly, we found that by using a Markov decision process, a simple scalar population model may be sufficient to guide harvest management of this species, even if its demography is age structured. Finally, we demonstrated how two different management objectives can lead to very different optimal harvesting strategies, and how conflicting objectives may be traded off with each other. This approach will have broad application for European waterbirds by providing preliminary estimates of key demographic parameters, by providing insights into the monitoring and research activities needed to corroborate those estimates, and by producing harvest management strategies that are optimal with respect to the managers' objectives, options, and available demographic information.

Disentangling the effects of multiple environmental drivers on population changes within communities.

The effects of different environmental drivers on the changes in species' population abundances can be difficult to disentangle as they often act simultaneously. Researchers have built statistical models that include environmental variables (such as annual temperature) or species attributes (such as a species' temperature preference), which are assumed to detect the impacts of specific drivers (such as climate change). However, these approaches are often applied separately or, if combined, not explicitly compared. We show the complementary insights gained by applying both these approaches to a community dataset on Danish terrestrial birds. We use our analysis to compare the relative importance of climate change and agricultural land-use change for the abundance changes within the community between 1983 and 2013. Population models were fitted to the community data of species' annual abundances with predictors comprising: species attributes (species' temperature and habitat preferences), environmental variables (climatic and agricultural land-use change variables) or both. Relationships between species' abundances and environmental variables were used to identify the drivers associated with average abundance changes of species in the community. Relationships between species' abundances and their attributes were used to understand the drivers causing interspecific variation in abundance changes. Warmer winters were positively associated with community-level abundances, and warm-adapted species had more positive abundance changes than cold-adapted ones. Agricultural land-use area was negatively associated with community-level abundances, and birds using a high proportion of meadow and habitat specialists had more negative abundance changes than birds using other habitats and habitat generalists. Effect sizes of environmental variables were larger for agricultural land-use change while those of species attributes were larger for climate change. The environmental data approach suggested that agricultural land-use change has decreased the average abundances of species in the community, affecting total community size while the species attribute-based approach suggested that climate change has caused variation in abundance among species, affecting community composition. Environmental variables and species attributes that are hypothesized to link to specific drivers can be used together to provide complementary information on the impacts of different drivers on communities.

The Arctic in the Twenty-First Century: Changing Biogeochemical Linkages across a Paraglacial Landscape of Greenland.

The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco- and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm.

Integrated population modelling reveals a perceived source to be a cryptic sink.

Demographic links among fragmented populations are commonly studied as source-sink dynamics, whereby source populations exhibit net recruitment and net emigration, while sinks suffer net mortality but enjoy net immigration. It is commonly assumed that large, persistent aggregations of individuals must be sources, but this ignores the possibility that they are sinks instead, buoyed demographically by immigration. We tested this assumption using Bayesian integrated population modelling of Greenland white-fronted geese (Anser albifrons flavirostris) at their largest wintering site (Wexford, Ireland), combining capture-mark-recapture, census and recruitment data collected from 1982 to 2010. Management for this subspecies occurs largely on wintering areas; thus, study of source-sink dynamics of discrete regular wintering units provides unprecedented insights into population regulation and enables identification of likely processes influencing population dynamics at Wexford and among 70 other Greenland white-fronted goose wintering subpopulations. Using results from integrated population modelling, we parameterized an age-structured population projection matrix to determine the contribution of movement rates (emigration and immigration), recruitment and mortality to the dynamics of the Wexford subpopulation. Survival estimates for juvenile and adult birds at Wexford and adult birds elsewhere fluctuated over the 29-year study period, but were not identifiably different. However, per capita recruitment rates at Wexford in later years (post-1995) were identifiably lower than in earlier years (pre-1995). The observed persistence of the Wexford subpopulation was only possible with high rates of immigration, which exceeded emigration in each year. Thus, despite its apparent stability, Wexford has functioned as a sink over the entire study period. These results demonstrate that even large subpopulations can potentially be sinks, and that movement dynamics (e.g. immigration) among winters can dramatically obscure key processes driving subpopulation size. Further, novel population models which integrate capture-mark-recapture, census and recruitment data are essential to correctly ascribing source-sink status and accurately informing development of site-safeguard networks.

Chewing Lice of Swan Geese (Anser cygnoides): New Host-Parasite Associations.

Chewing lice (Phthiraptera) that parasitize the globally threatened swan goose Anser cygnoides have been long recognized since the early 19th century, but those records were probably biased towards sampling of captive or domestic geese due to the small population size and limited distribution of its wild hosts. To better understand the lice species parasitizing swan geese that are endemic to East Asia, we collected chewing lice from 14 wild geese caught at 3 lakes in northeastern Mongolia. The lice were morphologically identified as 16 Trinoton anserinum (Fabricius, 1805), 11 Ornithobius domesticus Arnold, 2005, and 1 Anaticola anseris (Linnaeus, 1758). These species are known from other geese and swans, but all of them were new to the swan goose. This result also indicates no overlap in lice species between older records and our findings from wild birds. Thus, ectoparasites collected from domestic or captive animals may provide biased information on the occurrence, prevalence, host selection, and host-ectoparasite interactions from those on wild hosts.

Interactions between stoneworts (Charales) and waterbirds.

Stoneworts (Charales) are green algae that represent an important food resource for many waterbird species in Europe and elsewhere. Browsing avian herbivores (e.g. swan, goose, duck and coot species) consume Charales plant vegetative parts, by head-dipping, up-ending or diving. A lower fibre content and longer growing season may make Charales as attractive to such herbivores as sympatric submerged higher plant species in some circumstances. Charales respond to environmental stress (e.g. drought) by producing abundant diaspores, in the form of oospores (sexual) and bulbils (asexual), both rich in starch, generating abundant food for waterbirds at critical stages in their annual migratory cycles. Waterbirds feed on these by diving (e.g. common pochard Aythya ferina and red-crested pochard Netta rufina) or by filtering from the water column (e.g. dabbling duck species), ensuring dispersal of sexually produced and vegetative diaspores locally (because of predator swamping) and remotely (through endo- and ectozoochorous dispersal by long-distance migratory waterbirds). Greater invertebrate density and diversity associated with Charales canopies enhances their attractiveness over other submerged macrophyte beds to diving predators [e.g. tufted duck Aythya fuligula, common pochard and Eurasian coot Fulica atra (hereafter coot)]. Fish fry preying on these invertebrates use such vegetation as predator cover, in turn providing prey for avian piscivores such as grebes and cormorants. Abundant Charales contribute to maintaining a transparent water column due to canopy density, nutrient effects, dampening of sedimentation/remobilisation of suspended matter and nutrients and allelopathic effects on other plants (especially phytoplankton). Shallow, relatively eutrophic waters can flip between clear-water high-biodiversity (where Charales thrive) and turbid species-poor depauperate stable states (lacking Charales). Shifts between turbid conditions and rich submerged Charales beds have profound elevating effects on aquatic diversity, to which waterbirds show rapid aggregative responses, making them ideal indicator species of ecological change; in the case of Charales specialists (such as red-crested and common pochard), indicators of the presence and abundance of these plants. Large-bodied colonial nesting birds (e.g. cormorants, gulls, heron and egrets) aggregating along lake shores contribute high N and P loadings to water bodies sensitive to such external and internal inputs and can cause local eutrophication and potential loss of Charales. Despite variation from complete seasonal removal of Charales biomass to undetectable grazing effects by herbivorous birds, evidence suggests little effect of avian grazing on biomass accumulation or the stability of community composition (under otherwise stable conditions), but we urge more research on this under-researched topic. We also lack investigations of the relative foraging profitability of different Charales organs to waterbirds and the degree of viability of gyrogonites (fertilised and calcified oospores), vegetative bulbils and plant fragments after passage through the guts of waterbirds. We especially need to understand better how much the carbonate armour of these organs affects their viability/dispersal via waterbirds and urge more research on these neglected plants and their relationships and interactions with other organisms in the aquatic biota.

Food on a plate: Wild geese maintain higher food intake rates on uniform winter cereals fields versus diverse grasslands.

Spring staging Greater White-fronted Geese Anser albifrons have increasingly shifted from traditional diverse grassland fields to monocultures of winter cereals, causing conflict with farmers. To account for this transition, we tested two key predictions, controlling for goose age effects and sward height. Firstly, that cereal is better quality than grass (based on crude protein content). Secondly, that geese show higher peck rate and step rate on grassland than cereal, enabling them to compensate for lower, less selective intake rates there compared to the uniform, dense, high quality arable sward where all blades are equally of high profitability. Laboratory analyses showed that winter cereal had 27 % higher crude protein content than grass. Based on data extracted from video sequences of spring foraging geese in NE Poland, first-year birds ("immatures") showed significantly higher peck rates and step rates than adults in all situations, likely reflecting their less efficient foraging abilities. Both age classes showed significantly higher peck rates on grass than winter cereal as predicted. Combining differential protein content and lamina length/dry weight relationships of grass versus cereal showed that geese obtained 17-33 % more protein from cereal lamina of the same length. At observed peck rates, this equated to a 6 % greater hourly crude protein intake rate on cereals compared to grass at lamina length 2.5 cm, increasing to 29 % difference at 12.5 cm. Hence, at longer swards, cereals become increasingly profitable for foraging geese over grass swards, despite the higher peck rates observed on grass which failed to compensate for lower lamina quality. We contend that these interactions explain the simultaneous attraction of cereal over grass swards in this study area and likely elsewhere and we discuss the management implications of these findings.

Toxic lead gunshot persists accessible to waterbirds after a 33-year ban on their use.

Use of lead shot for hunting was banned under legislation on 26 Ramsar sites in Denmark from 1986, based on evidence of poisoning in waterbirds ingesting lead shot and high lead shot pellet densities in Danish wetland sediments caused by intensive hunting. To assess the fate of lead shot from hunting prior to 1986 and the degree to which such shot remains available to waterbirds, this study replicated the survey of shot pellet densities in substrates in Ringkøbing Fjord undertaken in the late 1970s. 287 shotgun pellets (282 lead, five steel) were recovered from 123 sediment samples at four locations, equivalent to a mean of 127 pellets m-2 in the top 20 cm of the sediment at the four locations, in certain hot spots equating to >250 kg lead ha-1, broadly similar to densities found in the 1970s. Possible explanations were given for the persistence of such high lead shot densities despite >30 years of regulation, during which time steel shot has been widely used as the alternative to lead. Field experiments showed that steel shot corroded in the marine environment, which likely contributes to lower steel shot densities found in this study. It is concluded that lead gunshot pellet dispersal and accumulation in natural ecosystems remains as a persistent and irreversible hazard to wildlife and ecosystems. Based on these Danish experiences, it is urgently recommended that international and national bodies in countries where hunting with lead shot continues recognise these results and act to prevent the accumulation of this toxic metal.

Consistent habitat preference underpins the geographically divergent autumn migration of individual Mongolian common shelducks.

While many avian populations follow narrow, well-defined "migratory corridors," individuals from other populations undertake highly divergent individual migration routes, using widely dispersed stopover sites en route between breeding and wintering areas, although the reasons for these differences are rarely investigated. We combined individual GPS-tracked migration data from Mongolian-breeding common shelduck Tadorna tadorna and remote sensing datasets, to investigate habitat selection at inland stopover sites used by these birds during dispersed autumn migration, to explain their divergent migration patterns. We used generalized linear mixed models to investigate population-level resource selection, and generalized linear models to investigate stopover-site-level resource selection. The population-level model showed that water recurrence had the strongest positive effect on determining birds' occupancy at staging sites, while cultivated land and grassland land cover type had strongest negative effects; effects of other land cover types were negative but weaker, particularly effects of water seasonality and presence of a human footprint, which were positive but weak or non-significant, respectively. Although stopover-site-level models showed variable resource selection patterns, the variance partitioning and cross-prediction AUC scores corroborated high inter-individual consistency in habitat selection at inland stopover sites during the dispersed autumn migration. These results suggest that the geographically widespread distribution (and generally rarity) of suitable habitats explained the spatially divergent autumn migrations of Mongolian breeding common shelduck, rather than the species showing flexible autumn staging habitat occupancy.

Lack of conspicuous sex-biased dispersal patterns at different spatial scales in an Asian endemic goose species breeding in unpredictable steppe wetlands.

Dispersal affects the spatial distribution and population structure of species. Dispersal is often male-biased in mammals while female-biased in birds, with the notable exception of the Anatidae. In this study, we tested genetic evidence for sex-biased dispersal (SBD) in the Swan Goose Anser cygnoides, an Asian endemic and IUCN vulnerable species, which has been increasingly restricted to breeding on Mongolian steppe wetlands. We analyzed the genotypes of 278 Swan Geese samples from 14 locations at 14 microsatellite loci. Results from assignment indices, analysis of molecular variance, and five other population descriptors all failed to support significant SBD signals for the Swan Goose at the landscape level. Although overall results showed significantly high relatedness within colonies (suggesting high levels of philopatry in both sexes), local male genetic structure at the 1,050 km distance indicated greater dispersal distance for females from the eastern sector of the breeding range. Hence, local dispersal is likely scale-dependent and female-biased within the eastern breeding range. These findings are intriguing considering the prevailing expectation for there to be female fidelity in most goose species. We suggest that while behavior-related traits may have facilitated the local genetic structure for the Swan Goose, several extrinsic factors, including the decreasing availability of the nesting sites and the severe fragmentation of breeding habitats, could have contributed to the absence of SBD at the landscape level. The long-distance molt migration that is typical of goose species such as the Swan Goose may also have hampered our ability to detect SBD. Hence, we urge further genetic sampling from other areas in summer to extend our results, complemented by field observations to confirm our DNA analysis conclusions about sex-specific dispersal patterns at different spatial scales in this species.

Status and trends of tundra birds across the circumpolar Arctic.

Tundra-breeding birds face diverse conservation challenges, from accelerated rates of Arctic climate change to threats associated with highly migratory life histories. Here we summarise the status and trends of Arctic terrestrial birds (88 species, 228 subspecies or distinct flyway populations) across guilds/regions, derived from published sources, raw data or, in rare cases, expert opinion. We report long-term trends in vital rates (survival, reproduction) for the handful of species and regions for which these are available. Over half of all circumpolar Arctic wader taxa are declining (51% of 91 taxa with known trends) and almost half of all waterfowl are increasing (49% of 61 taxa); these opposing trends have fostered a shift in community composition in some locations. Declines were least prevalent in the African-Eurasian Flyway (29%), but similarly prevalent in the remaining three global flyways (44-54%). Widespread, and in some cases accelerating, declines underscore the urgent conservation needs faced by many Arctic terrestrial bird species.

Effectiveness of the European Natura 2000 network to sustain a specialist wintering waterbird population in the face of climate change.

Analysis of coordinated Greater Scaup (Aythya marila) count data from the last 30 years showed a 38.1% decrease in wintering numbers in North-West Europe, from 309,000 during 1988-1991 to c.192,300 individuals during 2015-2018. Annual trends in wintering numbers differed throughout the range. Numbers decreased in the UK, Ireland, and in the Netherlands, while numbers were stable in Denmark. Germany, Poland, Sweden, and Estonia showed increasing numbers, suggesting a shift in the distribution of the species within its wintering grounds towards the east and north. Higher temperatures in northern and eastern areas were correlated with the range shift of the wintering distribution. Deaths from bycatch drowning of Scaup in fishing gear have significantly decreased in recent decades in the Netherlands, where currently the greatest threat is considered the deterioration of food resources. The increasing concentration of wintering Scaup in coastal Poland and Germany (where lack of effective implementation of conservation measures fail to protect the species from the impacts of bycatch and declining food quality) pose major threats to the entire population.

Lead concentrations in blood from incubating common eiders (Somateria mollissima) in the Baltic Sea.

Here we investigate if lead may be a contributing factor to the observed population decline in a Baltic colony of incubating eiders (Somateria mollissima). Body mass and blood samples were obtained from 50 incubating female eiders at the Baltic breeding colony on Christiansø during spring 2017 (n = 27) and 2018 (n = 23). All the females were sampled twice during early (day 4) and late (day 24) incubation. The full blood was analysed for lead to investigate if the concentrations exceeded toxic thresholds or changed over the incubation period due to remobilisation from bones and liver tissue. Body mass, hatch date and number of chicks were also analysed with respect to lead concentrations. The body mass (mean ± SD g) increased significantly in the order: day 24 in 2018 (1561 ± 154 g) < day 24 in 2017 (1618 ± 156 g) < day 4 in 2018 (2183 ± 140 g) < day 4 in 2017 (2359 ± 167 g) (all p < 0.001). The lead concentrations increased significantly in the opposite order i.e. day 4 in 2017 (41.7 ± 67.1 µg/L) < day 24 in 2017 (55.4 ± 66.8 µg/L) < day 4 in 2018 (177 ± 196 µg/L) < day 24 in 2018 (258 ± 243) (all p < 0.001). From day 4 to 24, the eider females had a 1.33-fold increase in blood lead concentrations in 2017 and a 1.46-fold increase in 2018. Three of the birds (13%) sampled in 2018 had lead concentrations that exceeded concentrations of clinical poisoning (500 µg/L) and eleven (48%) had concentrations that exceeded the threshold for subclinical poisoning (200 µg/L). In 2017, none of the birds exceeded the high toxic threshold of clinical poisoning while only one (4%) exceeded the lower threshold for subclinical poisoning. Three of the birds (6%) sampled in 2018 had lead concentrations that exceeded those of clinical poisoning while 12 birds (24%) resampled in both years exceeded the threshold for subclinical poisoning. In addition, lead concentrations and body mass on day 4 affected hatch date positively in 2018 (both p < 0.03) but not in 2017. These results show that bioavailable lead in bone and liver tissue pose a threat to the health of about 25% of the incubating eiders sampled. This is particularly critical because eiders are largely capital breeding which means that incubating eiders are in an energetically stressed state. The origin of lead in incubating eiders in the Christiansø colony is unknown and it remains an urgent priority to establish the source, prevalence and mechanism for uptake. The increase in lead from day 4 to day 24 is due to bone and liver remobilization; however, the additional lead source(s) on the breeding grounds needs to be identified. Continued investigations should determine the origin, uptake mechanisms and degree of exposure to lead for individual birds. Such research should include necropsies, x-ray, lead isotope and stable C and N isotope analyses to find the lead sources(s) in the course of the annual cycle and how it may affect the population dynamics of the Christiansø colony which reflects the ecology of the Baltic eiders being suitable for biomonitoring the overall flyway.

Intravascular mucormycosis as a cause of arm ischemia in an immunocompromised patient.

Mucormycosis is an opportunistic fungal infection primarily affecting patients with immunosuppression. We present a case of upper limb ischemia secondary to mucormycosis. A 59-year-old man with myelodysplasia presented with an acutely ischemic arm. The patient underwent numerous revascularisation attempts. Following the final procedure, he developed a cerebral infarct and subsequently died. The most common presentations of mucormycosis are of local character. Once established, it can spread rapidly with vascular invasion and in situ thrombosis. Mortality rate is 76%-96%. In this case, it led to fulminant intravascular coagulopathy resulting in recurrent upper and lower limb ischemia, and finally cerebral infarction.