Nesting common eiders (Somateria mollissima) show little behavioral response to fixed-wing drone surveys

Drones may be valuable in polar research because they can minimize researcher activity and overcome logistic, financial, and safety obstacles associated with wildlife research in Polar Regions. Because Polar species may be particularly sensitive to disturbance and some research suggests behavioral responses to drones are species-specific, there is a need for focal species-specific disturbance assessments. We evaluated behavioral responses of nesting Common Eiders (Somateria mollissima, n =19 incubating females) to first, second, or in a few cases third exposure of fixed-wing drone surveys using nest cameras. We found no effect of drone flights (F1,23 = 0, P < 1.0) or previous exposures (F1,23 = 0.75, P = 0.397) on the probability of a daily recess event (bird leaves nests). Drone flights did not impact recess length (F1,25 = 1.34, P = 0.26); however, eiders with prior drone exposure took longer recess events (F1,25 = 5.27, P = 0.03). We did not observe any overhead vigilance behaviors common in other species while the drone was in the air, which may reflect eider’s anti-predator strategies of reducing activity at nests in response to aerial predators. Surveying nesting common eider colonies with a fixed-wing drone did not result in biologically meaningful behavioral changes, providing a potential tool for research and monitoring this Polar nesting species.

Breeding Stage and Tissue Isotopic Consistency Suggests Colony-Level Flexibility in Niche Breadth of An Arctic Marine Bird

Organisms must overcome environmental limitations to optimize their investment in life history stages to maximize fitness. Human-induced climate change is generating increasingly variable environmental conditions, impacting the demography of prey items and therefore the ability of consumers to successfully access resources to fuel reproduction. While climate change effects are especially pronounced in the Arctic, it is unknown whether organisms can adjust foraging decisions to match such changes. We used a 9-year blood plasma δ13 C and δ15 N dataset from over 700 pre-breeding Arctic common eiders (Somateria mollissima) to assess breeding-stage and inter-annual variation in isotopic niche, and whether inferred trophic flexibility was related to colony-level breeding parameters and environmental variation. Eider blood isotope values varied both across years and breeding stages, and combined with only weak relationships between isotopic metrics and environmental conditions suggests that pre-breeding eiders can make flexible foraging decisions to overcome constraints imposed by local abiotic conditions. From an investment perspective, an inshore, smaller isotopic niche predicted a greater probability to invest in reproduction, but was not related to laying phenology. Proximately, our results provide evidence that eiders breeding in the Arctic can alter their diet at the onset of reproductive investment to overcome increases in the energetic demand of egg production. Ultimately, Arctic pre-breeding common eiders may have the stage- and year-related foraging flexibility to respond to abiotic variation to reproduce successfully.

Virio- and bacterioplankton of the Barents Sea in the autumn

The water area of the Kola Bay is an important place for marine and near-water birds during spring-autumn migrations and wintering periods. The results of counts of wintering birds in different parts of the bay in 2020–2021 are presented. The observations were carried out on the coast areas of the bay with the adjacent water area (Gryaznaya Bay, the area of the Kola Bridge). In general, in the southern and middle parts of the Kola Bay, the most numerous species in winter were common eider Somateria mollissima,long-tailed duck Clangula hyemalis, mallard Anas platyrhynchos, and glaucous gull Larus hyperboreus. During the observations, a relatively low nymber of wintering purple sandpipers Calidris maritima was noted in comparison to previous years. The composition of the bird fauna in the Kola Bay is fairly constant during the winter. Abrupt weather changes, such as warming, cooling, or snowstorms, c ause only small movements of birds within the wintering area.

Seasonal occurrence of waterbirds in Minas Passage, Bay of Fundy, Nova Scotia, Canada, 2010 to 2012

We determined patterns of seasonal abundance and diversity of seabirds and coastal waterfowl in Minas Passage, Bay of Fundy, Nova Scotia, Canada using quantitative, shore-based point surveys from mid-March to late August and mid-October to December 2010 to 2012. This area experiences the world’s highest tides and greatest tidal currents. We showed that species and seasonal cycles of waterbirds in Minas Passage reflect patterns typical of the inner Bay of Fundy and the northeast Atlantic coast of North America. The study highlights the importance of Minas Passage as an important local migration pathway for waterbirds including Black Scoter (Melanitta americana) and Red-throated Loon (Gavia stellata) passing through the Bay of Fundy. Large numbers of sea ducks (Black Scoter, Surf Scoter [Melanitta perspicillata], White-winged Scoter (Melanitta fusca), and Long-tailed Duck [Clangula hyemalis]), and Red-throated Loon were observed at the site in spring and fall, corresponding to known peak movements elsewhere in the Bay of Fundy. Fewest species and smallest abundances of waterbirds overall occurred in summer and early winter, while most species and largest abundances occurred in April-May and early November. Of the 46 species observed, resident breeders such as Herring Gull (Larus argentatus), Great Black-backed Gull (Larus marinus), Common Eider (Somateria mollissima), Black Guillemot (Cepphus grylle), and Double-crested Cormorant (Phalacrocorax auritus), were most abundant in spring to early summer during breeding and migrants including Red-throated Loon, Black Scoter, Ring-billed Gull (Larus delawarensis), Surf Scoter, and Northern Gannet (Morus bassanus) occurred in moderate numbers during migration periods.

Parental Investment Under Predation Threat in Incubating Common Eiders (Somateria mollissima): A Hormonal Perspective

Predation risk affects the costs and benefits of prey life-history decisions. Predation threat is often higher during reproduction, especially in conspicuous colonial breeders. Therefore, predation risk may increase the survival cost of breeding, and reduce parental investment. The impact of predation risk on avian parental investment decisions may be hormonally mediated by prolactin and corticosterone, making them ideal tools for studying the trade-offs involved. Prolactin is thought to promote parental care and commitment in birds. Corticosterone is involved in allostasis and may either mediate reduced parental investment (corticosterone-fitness hypothesis), or promote parental investment through a reallocation of resources (corticosterone-adaptation hypothesis). Here, we used these hormonal proxies of incubation commitment to examine the impact of predation risk on reproduction in common eiders (Somateria mollissima) breeding in the Baltic Sea. This eider population is subject to high but spatially and temporally variable predation pressure on adults (mainly by the white-tailed eagle Haliaeetus albicilla and introduced mammalian predators) and nests (by the adult predators and exclusive egg predators such as hooded crows Corvus cornix). We investigated baseline hormonal levels and hatching success as a function of individual quality attributes (breeding experience, female and duckling body condition), reproductive investment (clutch weight), and predation risk. We expected individuals nesting in riskier environments (i.e., on islands where predation on adults or nests is higher, or in less concealed nests) to reduce their parental investment in incubation, reflected in lower baseline prolactin levels and either higher (corticosterone-fitness hypothesis) or lower (corticosterone-adaptation hypothesis) baseline corticosterone levels. Contrary to our predictions, prolactin levels showed a positive correlation with nest predation risk. The unexpected positive relationship could result from the selective disappearance of low-quality females (presumably having low prolactin levels) from risky sites. Supporting this notion, female body condition and hatching success were positively correlated with predation risk on females, and baseline prolactin concentrations were positively correlated with duckling body condition, a proxy of maternal quality. In line with the corticosterone-adaptation hypothesis, baseline corticosterone levels increased with reproductive investment, and were negatively associated with nest predation risk. Hatching success was lower on islands where nest predation risk was higher, consistent with the idea of reduced reproductive investment under increased threat. Long-term individual-based studies are now needed to distinguish selection processes occurring at the population scale from individually plastic parental investment in relation to individual quality and variable predation risk.

Common Eider Wintering Trends in Nova Scotia, 1970–2019

Common eiders Somateria mollissima have been a focus of conservation and management efforts in eastern North American for over a century; however, the complex population structure and multiple subspecies make assessing the status of populations challenging. The coastlines of Nova Scotia, Canada, are an important wintering area for common eiders, and significant harvests of common eiders occur in the province. We analyzed trends in the number of wintering common eiders using the coasts of Nova Scotia from dedicated waterfowl surveys flown since 1970, and every year since 1992. We used Generalized Additive Models to assess the apparent non-linear trends in the counts of common eiders over the past 50 y. We found that numbers of common eiders wintering in Nova Scotia increased from 1970 to the early 2010s, with strong growth in the 2000s (peaking at 7% growth/y). Since the early 2010s, the growth has stopped, and the numbers are now declining. Recent declines in the population wintering in Nova Scotia corroborate other evidence that common eiders are declining in the region, and may also indicate distributional shifts of common eiders in eastern North America.

Polar bears are inefficient predators of seabird eggs

Climate-mediated sea-ice loss is disrupting the foraging ecology of polar bears ( Ursus maritimus ) across much of their range. As a result, there have been increased reports of polar bears foraging on seabird eggs across parts of their range. Given that polar bears have evolved to hunt seals on ice, they may not be efficient predators of seabird eggs. We investigated polar bears' foraging performance on common eider ( Somateria mollissima ) eggs on Mitivik Island, Nunavut, Canada to test whether bear decision-making heuristics are consistent with expectations of optimal foraging theory. Using aerial-drones, we recorded multiple foraging bouts over 11 days, and found that as clutches were depleted to completion, bears did not exhibit foraging behaviours matched to resource density. As the season progressed, bears visited fewer nests overall, but marginally increased their visitation to nests that were already empty. Bears did not display different movement modes related to nest density, but became less selective in their choice of clutches to consume. Lastly, bears that capitalized on visual cues of flushing eider hens significantly increased the number of clutches they consumed; however, they did not use this strategy consistently or universally. The foraging behaviours exhibited by polar bears in this study suggest they are inefficient predators of seabird eggs, particularly in the context of matching behaviours to resource density.

Brain mass explains prey size selection better than beak, gizzard and body size in a benthivorous duck species

Prey size selection in some bird species is determined by the size of the beak. However, we assumed for bird species swallowing whole prey that a cognitive process may be involved. As cognitive feature, brain mass was used. We hypothesized that the mass of the brain was more strongly positively correlated with prey size than morphological features such as beak volume, gizzard mass and body mass. We tested this hypothesis on eiders Somateria mollissima that swallow the prey whole, by using mean and maximum size of nine prey categories. Eiders were collected at the main wintering grounds in Denmark. As index of brain mass we used head volume, which is positively correlated with brain mass (r2 = 0.73). Head volume of eiders was significantly, positive correlated with mean and maximum size of blue mussels Mytilus edulis, razor clams Ensis directus and all prey sizes combined and the maximum size of draft whelk Hinia reticulata and conch Buccinum undatum. Gizzard mass was also significantly positively correlated with maximum size of draft whelk and conch. Beak volume and body mass was not significantly correlated with the size of any of the nine food items. Analyses of effect size for organs showed that head volume was positively related to prey size, whereas beak volume, gizzard mass and body mass did not show a significant positive relationship. These results indicate that cognitive processes connected to brain mass may be involved in prey size selection by eiders.