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The purpose of the present study was to determine the link between planktivorous little auks (Alle alle) and their soil fertilization, the concentration of total, and different forms of phosphorus in the surface layer of the High Arctic soils and the vascular plant composition of the tundra vegetation. Samples of the surface soil layer (0–10 cm) were collected along three pairs of transects (affected and unaffected by little auks) at different locations in Spitsbergen (Svalbard). The surface layer of soils affected by little auks was characterized by a significantly higher mean concentration of Ptot (1.02–1.44 g kg−1) compared to those not affected by seabirds (0.58–0.77 g kg−1). The mean concentration of different forms of P was also generally higher in soils affected by seabirds (i.e., labile P: 0.13–0.34 g kg−1, moderately labile P: 0.31–0.90 g kg−1, stable P: 0.27–0.39 g kg−1) than in unaffected soils (labile P: 0.04–0.18 g kg−1, moderately labile P: 0.30–0.37 g kg−1, stable P: 0.12–0.24 g kg−1); however, the differences were not always significant, most likely due to the high heterogeneity of specific environmental conditions at the local scale such as soil type, soil chemical composition, and vegetation type. Vascular plant cover was significantly and positively related to the concentration of the P forms studied in the soil. The phosphorus gradient significantly altered the composition of the vascular plants and explained 58.4% of its variation. Little auks are an important source of soil phosphorus in terrestrial ecosystems in the High Arctic that significantly affect the cover and composition of vascular plants.

The Little Auk Alle alle is a small planktivorous auk breeding colonially in the High Arctic. Owing to its large population size and bi-environmental lifestyle, resulting in the large-scale transport of matter from sea to land, the Little Auk is one of the most important components of the marine and terrestrial ecosystems in the Arctic. As a result of globalization, which facilitates access to remote areas of the Earth, a growing number of studies is being dedicated to this endemic Arctic seabird. Research has focussed primarily on the importance of the Little Auk as an ecological indicator reacting to the climatic and oceanological changes that are particularly evident in the Arctic as a result of Arctic amplification (warming is more rapid in the Arctic than in any other region on Earth). Importantly, the species is also used as a model to investigate matter and energy flow through the ecosystem, mate choice, parental care and biological rhythms. Here, we review the natural history of the Little Auk, highlighting studies with the potential to provide answers to universal questions regarding the response of seabirds to climate variability and avian reproductive behaviour, e.g. threshold of foraging flexibility in response to environmental variability, carry-over effects between the breeding and non-breeding periods, the reasons for the transition from bi- to uni-parental care, parental coordination mechanisms.

The polar bearUrsus maritimusis one of the species most endangered by the rapidly declining sea–ice cover in the Arctic, which they use as a platform to hunt fatty, high-energy seals. In recent decades, more polar bears have been forced to remain longer on land, so their access to seals is limited. The importance of terrestrial food to polar bears is disputable, and more data are needed. Terrestrial ungulates could be an attractive substitute prey for them. Svalbard reindeerRangifer tarandus platyrhynchusare prevalent and their distribution is completely within the range of polar bears. They constitute an attractive potential prey offering a significant energy return. Pre-2000 sources state that polar bears do not attack Svalbard reindeer. This report is the first description and documentation of the complete course of a polar bear hunt for adult reindeer in Hornsund, SW Spitsbergen, and also of the bear’s hunting behaviour and the reindeer’s response. Further, we report several other recent instances of bear–reindeer interactions in Svalbard, suggesting that polar bears now hunt reindeer more frequently than they used to. This increase in hunting is probably linked to the reduced ice cover, with bears spending more time on land, and a growing reindeer population. This study adds to earlier papers on how polar bears in Svalbard have increasingly shifted to a more terrestrial diet, and indicates that they may have an enhanced role as an apex predator in the terrestrial ecosystem.

Assessment of the impact of climate change on the Arctic nearshore ecosystems requires knowledge of the “reference points”, that is, the state of things before the effects of the warming become pronounced. For parasites, which play an essential role in the nearshore ecosystems, this knowledge is scarce and fragmentary. This study, based on the materials collected at Franz Josef Land (FJL) in 1990–1993, partly fills this gap. We present the first data on the diet of the common eider Somateria mollissima at FJL, the transmission of helminths in its population and the infection of nearshore invertebrates with helminth larvae. We found that gastrointestinal helminth communities were impoverished (only ten species) and dominated by cestodes and acanthocephalans. This is associated with the prevalence of nearshore crustaceans, the intermediate hosts of these helminths, in the diet of the eiders. The absence of the vulnerable free-living larvae also facilitates transmission of helminths parasitizing eiders at FJL. Infection with helminths and the diet were different in ducklings and in adult birds as well as in eiders from different parts of the archipelago. The infection distribution of molluscs and crustaceans with helminth larvae was patchy and higher in the vicinity of the eider colonies. A high-infection intensity of FJL eiders with cestodes and acanthocephalans recorded in our study seems to have a certain negative effect on the bird population. Its significance is likely to grow considering that the transmission of helminths is promoted by the climate warming in the Arctic.

To monitor the rapid changes occurring in Arctic ecosystems and predict their direction, basic information about the current number and structure of the main components of these systems is necessary. Using boat-based surveys, we studied the numbers and distribution of seabirds foraging in Hornsund (SW Spitsbergen) during three summer seasons. The average number of seabirds foraging concurrently in the whole fjord was estimated at 28,000. Little Auks Alle alle were the most numerous, followed by Northern Fulmars Fulmarus glacialis, Brünnich’s Guillemots Uria lomvia and Black-legged Kittiwakes Rissa tridactyla. The pelagic zone was exploited by some 75% of the birds. Their density was the highest (> 400 ind. km−2) in the tidewater glacier bays, where kittiwakes were predominant, and the lowest in the coastal glacier bays. The seabirds in Hornsund daily consumed c. 12.7 tons of food, i.e. c. 0.2% of the summer mesozooplankton and fish standing stocks available in the fjord. This food consisted primarily of copepods, amphipods and molluscs (c. 70%), whereas fish made up

Using GPS-tracked individuals, we compared foraging ecology and reproductive output of a High-Arctic zooplanktivorous seabird, the little auk Alle alle, between three years differing in environmental conditions (sea surface temperature). Despite contrasting environmental conditions, average foraging fights distance and duration were generally similar in all studied years. Also, in all years foraging locations visited by the little auk parents during short trips (ST, for chick provisioning) were significantly closer to the colony compared to those visited during long trips (LTs, mainly for adults’ self-maintenance). Nevertheless, we also found some differences in the little auk foraging behaviour: duration of LTs was the longest in the coldest year suggesting more time for resting for adults compared to warmer years. Besides, birds foraged closer to the colony and in significantly colder water in the coldest year. Interestingly, these differences did not affect chick diet: in all the years, the energy content of food loads was similar, with the Arctic copepod, Calanus glacialis copepodite stage V being the most preferred prey item (>73% of items by number and >67% by energy content). Also chick survival was similar in all the study years. However, when examining chicks growth rate we found that their peak body mass was lower in warmer years suggesting that overall conditions in the two warm years were less favourable. While our results, demonstrate a great foraging flexibility by little auks, they also point out their vulnerability to changing environmental conditions.

Despite widespread recognition of the crucial role seabirds play in the fertilization of nutrient-poor polar terrestrial ecosystems, no studies have attempted a concurrent analysis of the entire or large proportion of an ornithogenically-supported food web. The aim of the current study was to assess the significance of allochthonous nutrient enrichment of key elements of the Bjornoya (Svalbard) terrestrial ecosystem by investigating how different seabird species influenced the characteristics of soil, vegetation, and soil invertebrates (direct ornithogenic effects), and also how those characteristics were interrelated (indirect ornithogenic effects). We sampled in the vicinity of a little auk ( Alle alle ) colony, and in areas occupied by great skua ( Stercorarius skua ) and glaucous gull ( Larus hyperboreus ) nests. Our data demonstrate clear, multi-trophic-level, ornithogenic impacts across the terrestrial ecosystem, with most of the measured parameters of soil, vegetation and invertebrates being altered by proximity to bird nesting areas, though to varying degrees. The ornithogenic effects tended to weaken with increasing complexity of interactions between the ecosystem components, with progression through successive trophic levels. The clearest responses were observed for soil (higher nitrogen stable isotope ratio δ 15 N, nitrogen and water content) and vegetation characteristics (higher δ 15 N, N content and total cover, lower diversity and species number, and modified community composition). The responses seen in the invertebrate communities were less clear (community composition change), and were only apparent when major invertebrate groups were considered together and for the assumed decomposers: springtails and oribatid mites, while not in the case of predators (mesostigmatid mites and one spider species). There were also suggestions in the data that different seabird species may have different impacts on the surrounding environment, probably due to their different diet and nesting area topography. However, generally, the species of bird was a weaker factor than the presence of a seabird colony or nest itself.

Here, we model current and future distribution of a foraging Arctic endemic species, the little auk (Alle alle), a small zooplanktivorous Arctic seabird. We characterized environmental conditions [sea depth, sea surface temperature (SST), marginal sea ice zone (MIZ)] at foraging positions of GPS-tracked individuals from three breeding colonies in Svalbard: one located at the southern rim of the Arctic zone (hereafter ‘boreo-Arctic’) and two in the high-Arctic zone on Spitsbergen (‘high-Arctic’). The birds from one ‘high-Arctic’ colony, influenced by cold Arctic water, foraged in the shallow shelf zone near the colony. The birds from remaining colonies foraged in a wider range of depths, in a higher SST zone (‘boreo-Arctic’) or in the productive but distant MIZ (second ‘high-Arctic’ colony). Given this flexible foraging behaviour, little auks may be temporarily resilient to moderate climate changes. However, our fuzzy logic models of future distribution under scenarios of 1 °C and 2 °C SST increase predict losses of suitable foraging habitat for the majority of little auk colonies studied. Over longer time scales negative consequences of global warming are inevitable. The actual response of little auks to future environmental conditions will depend on the range of their plasticity and pace of ecosystem changes.

Summary Two high latitude fjords of Spitsbergen (Hornsund 77°N and Kongsfjorden 79°N) are regarded as being highly productive (70 g and 50 gC m −2 year −1 ) and having organic-rich sediments. Hornsund has more organic matter in its sediments (8%), nearly half of it of terrestrial origin, while most of that in Kongsfjorden (5%) comes from fresh, marine sources (microplankton). Analysis of the carbon sources in both fjords shows that a major difference is the much larger seabird population in Hornsund-dominated with over 100 thousands pairs of plankton feeding little auks in Hornsund versus 2 thousand pairs in Kongsfjorden, and marine food consumption estimated as 5573 tonnes of carbon in Hornsund, versus 3047 tonnes in Kongsfjorden during one month of chick feeding period. Seabird colonies supply rich ornithogenic tundra (595 tonnes of C, as against only 266 tonnes of C in the Kongsfjorden tundra). No much of the terrestrial carbon, flushed out or wind-blown to the fjord, is consumed on the seabed – a state of affairs that is reflected by the low metabolic activity of bacteria and benthos and the lower benthic biomass in Hornsund than in Kongsfjorden.

Arctic terrestrial ecosystems are particularly vulnerable to the effects of ongoing and predicted climate changes. The current states of environmental biodiversity and ecological networks in the Arctic need to be known and understood to monitor how they change and how these changes may influence the particular components of the ecosystem. Despite the fact that the Arctic tundra is generally poor in nutrients, it has a surprisingly high biodiversity, especially of invertebrates and microorganisms. Besides macroclimatic features, there may be local factors influencing biodiversity, such as microclimate, water availability, or large seabird colonies depositing guano. This last can have a substantial impact on the soil’s physicochemical features, and consequently the distribution, number, and diversity of tundra-associated plants and animals in the vicinity of the colony. Changes in the Arctic biodiversity and the functioning of the ecosystem at all trophic levels are difficult to investigate using traditional methods. In this review, we discuss how modern molecular techniques, including next generation sequencing, influence our ability to investigate and understand this ecosystem at both the micro- and the macroscale and how they can complement the more traditional approaches to studying ecological networks in the Arctic.

Climate-induced glacier retreat is considered in the context of its reducing the sea-ice contact zone used by marine birds and mammals as important foraging grounds and may cause declines in their numbers. To test this hypothesis, a survey was conducted in diversified habitats of a rapidly deglaciating Arctic fjord in Svalbard. Of the fifteen seabird and four mammal species found, coastal surface-feeders prevailed over benthic-feeders and pelagic pursuit-divers. Deep tidewater glacier bays were used by the most numerous but least heterogeneous foraging community, in contrast to the shallow lagoons of coastline-terminating glaciers and deglaciated shorelines. After the 15 years of glaciers retreat documented in Hornsund, the sea-ice contact zone used by birds and mammals has not declined. On the contrary, the increasing freshwater supply from underwater glacial rivers raising zooplankton up to the surface, thus making it available to seabirds, enhances the attractiveness of tidewater glacier bays. Along with the stage of retreat, the importance of glacier bays as feeding grounds changes. Foraging conditions deteriorate when the glacier terminus reaches the coastline and the glacier bay becomes shallower. However, glacier retreat enlarges the area of littoral habitats accessible to benthophages. Glacier-related habitats situated close to colony are used as alternative/emergency feeding grounds by seabirds that normally forage outside the fjord. This is especially important during the chick-rearing period and also during bad weather conditions in the open sea. Our study demonstrates that, so far, the abundance and species diversity of seabirds foraging in the rapidly deglaciating Hornsund are both high, suggesting that they benefit from the current intensive glacier melt. However, with further climate change an apparent biodiversity paradox may occur. Here, overall biodiversity will increase but local diversity of pagophilic species will decline. Such nonlinear responses complicate the prediction of future polar ecosystem dynamics.

Zooplanktivorous seabirds as central-place foragers are constrained by the need to repeatedly return to the colony. Breeding within a cost-effective distance from food-abundant foraging grounds may be crucial for successful reproduction. In this study, foraging areas, ranges and habitats of high-Arctic little auks ( Alle alle ) breeding on Bjornoya in the Barents Sea, at the southern edge of their breeding range, were investigated combining GPS-tracking and satellite remote sensing. Birds were expected to forage in areas with productive oceanographic features (cold shelf and frontal zone waters) close to their breeding colony. Contrary to expectation, they foraged in warm waters (sea surface temperature median 6.6 °C), optimal for boreal zooplankton. Little auks preferred shallow shelf waters (mean depth 74 m) characterized by higher chlorophyll a concentrations. Parent birds performed both short (ST) and long (LT) foraging trips, both of considerably longer duration compared to other colonies in more high-Arctic environment. During ST they probably spent more time searching for preferred Arctic prey (dominating in chick diet samples) among abundant Atlantic zooplankton. Long duration of LT resulted from exploring distant cold waters abundant in Arctic zooplankton community. This confirms that little auks are able to respond to various environmental conditions through the plasticity of their foraging behavior without negative consequences for chick survival. To date, observed changes in marine environment have not posed a threat to the ability of little auks on Bjornoya to feed their chicks energy-rich zooplankton.

Different phenological responses to climate changes by species representing preys and predators may lead to mismatch between functionally dependent components of an ecosystem, with important effects on its structure and functioning. Here, we investigate within-season variation in zooplankton availability, chick diet composition and breeding performance of a small planktivorous seabird, the little auk (Alle alle) in two large colonies in Hornsund and Magdalenefjorden, Spitsbergen, differing in synchrony of breeding (11-day vs. 22-day hatching period, respectively). Assuming similar zooplankton phenology and existing differences in duration of the little auk breeding period, we expected lower availability of the preferred food in the less synchronized colony in Magdalenefjorden and in consequence a negative effect on nestling body mass and survival. We found that in both colonies Calanus glacialis (copepodite stage CV) was the most important prey item in the chick diet making up 68–87 % of the biomass and energy of all prey items. The only exception was the end of the chick-rearing period in Magdalenefjorden, when contribution of this prey item was significantly lower (24–26 %). Thus, late breeders in Magdalenefjorden were apparently mismatched regarding C. glacialis CV availability. However, the hatching date did not affect birds fitness (reproductive output and chick pre-fledging mass) significantly. Results of our study indicate that little auks breeding on Spitsbergen can respond to a wide range of environmental conditions and prey availabilities through the plasticity of their foraging behaviour, which may help them to maintain their optimum fitness level in changing and unpredictable environments.

The diversity of cyanobacteria and algae from various microhabitats in Spitsbergen is comparatively well known. However, the relationships between environmental factors and the structure of microflora communities remain largely unclear. This study was conducted in Hornsund Bay, which exhibits large variability in the physicochemical characteristics of habitats, particularly with regard to the availability of nitrogen and phosphorus. This variability, to a large degree, is caused by seabird colonies, which fertilize nutrient-poor terrestrial ecosystems near their nesting areas. The large variations in ecological conditions and vegetation types in the study area aid assessment of habitats representing different combinations of factors potentially influencing the formation of cyanobacterial and algal assemblages. The aim of this study was to examine the influence of physicochemical parameters on the taxonomic composition and diversity of green algae and cyanobacteria (particularly the coccoid, oscillatorialean, and heterocystous taxa). The study encompassed two groups of habitats – soil surface habitats and water-saturated habitats, both characterized by diverse influences of seabird colonies, vegetation cover, and moisture. Our results showed that taxonomic diversity and composition of cyanobacteria and algae were mainly influenced by P–PO43−, N–NH4+ and Ca2+ (soil surface habitats), and NO3−, as well as moisture (index of wetness) and pH (water-saturated habitats). The variability of these physicochemical properties was largely due to the variability of the seabird colony influence. Taken together, our findings aid in understanding the processes of formation of phycoflora assemblages in Arctic tundra.

Background Foraging strategies of seabird species often vary considerably between and within individuals. This variability is influenced by a multitude of factors including age, sex, stage of annual life cycle, reproductive status, individual specialization and environmental conditions. Results Using GPS-loggers, we investigated factors affecting foraging flight characteristics (total duration, maximal range, total distance covered) of great skuas Stercorarius skua of known sex breeding on Bjørnøya, Svalbard, the largest colony in the Barents Sea region. We examined influence of sex (females are larger than males), phase of breeding (incubation, chick-rearing), reproductive status (breeders, failed breeders) and bird ID (they are known for individual foraging specialization). Our analyses revealed that only bird ID affected foraging flight characteristics significantly, indicating a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized three main groups of individuals: 1) those preying mainly on other seabirds in the breeding colonies (6%), 2) those foraging at sea (76%) and kleptoparasiting other seabirds and/or foraging on fish and/or offal discarded by fishing vessels, and 3) those alternating between preying on other seabirds in breeding colonies and foraging at sea (18%). Despite marked size sexual dimorphism, we found no apparent sex differences in flight characteristics. Birds after egg- or chick-loss and thus not constrained as central foragers did not modify their foraging flights. Conclusions Great skuas breeding on Bjørnøya displayed a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized groups of individuals regularly preying in the seabird colonies, foraging at sea, and alternating between both strategies. This suggests foraging specialization of some individuals.

In spite of general knowledge that guano deposited near seabird colonies enhances fertility of poor polar soils, improves primary production and influences the tundra plant community, there are very few quantitative studies concerning plant responses to ornithogenic fertilization on the population level. We studied density, size variability and proportions of generative to vegetative individuals of polar scurvygrass Cochlearia groenlandica along a seabird influence gradient in south-west Spitsbergen. We found the seabird colony effect to being a predominant factor determining local ascurvygrass population structure. Plant density was increasing starting from the foot of the cliff (820 ind/m2) and reaching the highest value (7500 ind/m2) about 30 m from the colony. This density peak was a result of the flowering plants occurring in the area above in the highest number which produced plenty of seeds germinating several metres below. The density of flowering plants was significantly correlated with the physical and chemical features of the soil but concerned only small individuals (1–4 cm), whose numbers were negatively correlated with the level of available nutrients, and large-sized (13–20 cm) plants, which were correlated positively. The only significant factor influencing flowering plant density along the bird colony gradient was the content of organic matter in the soil. In the control transect, total plant density was three orders of magnitude lower. No or weak correlations were found between plant density and soil characteristics along that transect. Our study supports the hypothesis that seabirds have fundamental importance not only for vegetation abundance in the nutrient-poor Arctic environment but also to determine plant population structure in the vicinity of large breeding colonies.

Although the processes occurring at the front of an ice face in tidewater glacier bays still await thorough investigation, their importance to the rapidly changing polar environment is spurring a considerable research effort. Glacier melting, sediment delivery and the formation of seabird foraging hotspots are governed by subglacial discharges of meltwater. We have combined the results of tracking black-legged kittiwakes Rissa tridactyla equipped with GPS loggers, analyses of satellite images and in situ measurements of water temperature, salinity and turbidity in order to examine the magnitude and variability of such hotspots in the context of glacier bay hydrology. Small though these hotspots are in size, foraging in them appears to be highly intensive. They come into existence only if the subglacial discharge reaches the surface, if the entrainment velocity at a conduit is high and if there is sufficient macroplankton in the entrainment layer. The position and type of subglacial discharges may fluctuate in time and space, thereby influencing glacier bay hydrology and the occurrence of foraging hotspots.

Observed large-scale changes in climate and oceanography, which are especially pronounced in the Arctic, represent profound challenges for upper trophic predators. Knowledge about the extent to which marine predators are able to adjust to environmental variability is essential in order to assess the impact of changing oceanic conditions on the Arctic ecosystem. The main goal of this study was to investigate the impact of oceanographic conditions that varied on an inter-annual and inter-colony basis on the foraging and breeding strategy of a zooplanktivorous alcid, the little auk Alle alle. The study was conducted in two little auk breeding colonies in Spitsbergen (Hornsund and Magdalenefjord) located in different hydrographical regimes in two contrasting seasons (2009 and 2010). This article provides a comprehensive study linking a number of variables describing foraging ground quality, measured directly at sea, with the birds' foraging strategy, parental efforts, body condition and survival of ne...

Energy and time allocation diff ers between incubation and chick-rearing periods, which may lead to an adjustment in the foraging behaviour of parent birds. Here, we investigated the foraging behaviour of a small alcid, the little auk Alle alle during incubation and compared it with the chick-rearing period in West Spitsbergen, using the miniature GPS (in Hornsund) and temperature loggers (in Magdalenefj orden). GPS-tracking of 11 individuals revealed that during incubation little auks foraged 8 – 55 (median 46) km from the colony covering 19 – 239 (median 120) km during one foraging trip. Distance from the colony to foraging areas was similar during incubation and chick-rearing period. During incubation 89% of foraging positions were located in the zone over shallower parts of the shelf (isobaths up to 200 – 300 m) with sea surface temperature below 2.5 ° C. Th ose environmental conditions are preferred by Arctic zooplankton community. Th us, little auks in the Hornsund area restrict their foraging (both during the incubation and chick-rearing period) to the area under infl uence of cold, Arctic-origin water masses where its most preferred prey, copepod Calanus glacialis is most abundant. Th e temperature logger data (from 4 individuals) indicate that in contrast to the chick-rearing period, when parent birds alternated short and long trips, during the incubation they performed only long trips. Adopting such a fl exible foraging strategy allows little auks to alter their foraging strategy to meet diff erent energy and time demands during the two main stages of the breeding.

In the resource-limited Arctic environment, vegetation developing near seabird colonies is exception- ally luxuriant. Nevertheless, there are very few detailed quantitative studies of any specific plant species responses to ornithogenic manuring. Therefore, we studied variability of polar scurvygrass Cochlearia groenlandica individual biomass and leaf width along a seabird influenced gradient determining environmental conditions for vegetation in south-west Spitsbergen. We found seabird colony effect being a paramount factor responsible for augmented growth of C. groenlandica. The species predominated close to the colony and reached the highest mean values of individual biomass (1.4 g) and leaf width (26.6 mm) 10 m below the colony. Its abundance and size declined towards the coast. Both C. groenlandica individual traits signifi- cantly decreased with distance from the colony, soil water and organic matter content and increased with guano deposition, soil d 15 N, conductivity, acidity and nitrate, phosphate and potassium ion content. Our study supports the hypothesis that seabirds have fundamental importance for vegetation growth in poor Arctic environment. Highly plastic species such as C. groenlandica may be a useful instrument in detecting habitat condition changes, for instance resulting from climate change.

2 Institute of Oceanology, Polish Academy of Sciences, ul. Powstancow Warszawy 55, 81-712 Sopot, Poland ABSTRACT: Knowledge of foraging behaviour is essential to understand both the ecological roles of seabirds and the constraints acting upon them in marine ecosystems. Here, we investigated for- aging trips of a small planktivorous alcid, the little auk Alle alle, using miniature GPS loggers. We performed the study in 2 large breeding colonies in west Spitsbergen (Hornsund and Magdalene- fjorden) with contrasting oceanographic conditions (Arctic and Atlantic environments, respec- tively). Generally, in both locations little auks foraged in areas with low sea surface temperature (Arctic-type water, marginal ice zone, and frontal zones) where preferred zooplankton are com- monly abundant. In the Arctic environment (Hornsund), birds foraged significantly closer to the colony (up to 60 km) compared to up to 150 km in the Atlantic environment (Magdalenefjorden). Hatching and breeding success and chick survival up to 20 d as well as chick body mass para - meters were similar in both studied colonies. However, chicks in the Arctic environment (Horn- sund) achieved both peak body mass and fledging age earlier, suggesting faster chick growth than in the Atlantic environment (Magdalenefjorden). The importance for breeding little auks of nearby cold water foraging grounds may make them sensitive to predicted climate change with serious negative consequences for body condition, future survival and breeding success.

As diving seabirds use vision underwater, it is presumed they should preferentially select sites where their preferred food items are not only abundant but also clearly visible. To test this, we studied the optical properties of the seawater in the West Spitsbergen Shelf, in combination with zooplankton abundance in the feeding grounds of the planktivorous little auks from the nearby colonies in Hornsund. We estimated the relative attractiveness of the foraging sites using a novel parameter—visual prey availability (VPAv), which relates density and proportion of the preferred food item (Calanus glacialis) of the little auk, in total zooplankton, to the optical properties of the seawater. We found a significant positive correlation between the density of foraging little auks and VPAv values. Birds chose areas where C. glacialis was both abundant and clearly visible, because of the clarity of the water and low proportion of other zooplankton species. The birds avoided foraging over the warmer Atlantic-type waters, characterised by a high abundance of zooplankton taxa mostly ignored by birds and where VPAv values were low. VPAv values could potentially also be applied to other visual planktivores for which prey preference and visual acuity are known.

Prolonged chasing of an adult reindeer (Rangifer tarandus) by a polar bear (Ursus maritimus) was observed both on land and in the sea, in Magdalenefjorden, northwest Spitsbergen. Polar bears were also observed catching black guillemot (Cepphus grylle) in the sea in northwest Spitsbergen and feeding on chicks in the arctic tern (Sterna paradisea) colony in Hornsund, southwest Spitsbergen. While feeding on seabird species is unsurprising, the prolonged chasing of adult reindeer is unusual for polar bear hunting behaviour. The few documented cases of polar bear hunting reindeer consist of either surprising and killing resting/sleeping prey or stalking and a short rapid chase of the reindeer. Our observations describe new feeding habits of polar bears that may be in response to decreasing seal availability due to shrinking sea-ice cover in the Arctic.

The role of seabirds as sea-land biovectors of nutrients is well documented. However, no studies have examined whether and how colonial seabirds that differ in diet may influence terrestrial vegetation. Therefore, the purpose of the study was to describe and compare plant communities located in the vicinity of the two most common types of seabird colonies in Arctic, occupied by piscivorous or planktivorous species. Within 46 plots arranged in four transects in the vicinity of planktivorous (little auk, Alle alle) and piscivorous colonies (mixed colony of Brunnich’s guillemot, Uria lomvia, and black-legged kittiwake, Rissa tridactyla) we measured the following: guano deposition, physical and chemical characteristics of soil, total nitrogen and its stable isotope signatures in soil and plants, ground vegetation cover of vascular plants and mosses, and the occurrence of lichens, algae and cyanobacteria. Using LINKTREE analysis, we distinguished five plant communities, which reflected declining influence along a birds fertilization gradient measured as guano deposition. SIMPROOF test revealed that these communities differed significantly in species composition, with the differences related to total soil nitrogen content and δ15N, distinctive levels of phosphates, potassium and nitrates, and physical soil properties, i.e., pH, conductivity and moisture. The communities were also clearly distinguished by distance from the bird colony. The two colony types promoted development of specific plant communities: the immediate vicinity of the planktivorous colony characterized by a Deschampsia alpina–Cerastium arcticum community while under the piscivorous colony a Cochlearia groenlandica–Poa alpina community was present. Despite the similar size of the colonies and similar magnitude of guano input, differences between ornithogenic communities were connected mostly to phosphate content in the soil. Our results show that the guano input from seabirds which have different diets can affect High Arctic vegetation in specific and more complex ways than previously realized.

Due to deposition of birds' guano, eggshells or feathers, the vicinity of a large seabirds' breeding colony is expected to have a substantial impact on the soil's physicochemical features as well as on diversity of vegetation and the soil invertebrates. Consequently, due to changing physicochemical features the structure of bacterial communities might fluctuate in different soil environments. The aim of this study was to investigate the bacterial assemblages in the Arctic soil within the area of a birds' colony and in a control sample from a topographically similar location but situated away from the colony's impact area. A high number of OTUs found in both areas indicates a highly complex microbial populations structure. The most abundant phyla in both of the tested samples were: Proteobacteria, Acidobacteria, Actinobacteria, and Chloroflexi, with different proportions in the total share. Despite differences in the physicochemical soil characteristics, the soil microbial community structures at the phylum level were similar to some extent in the two samples. The only share that was significantly higher in the control area when compared to the sample obtained within the birds' colony, belonged to the Actinobacteria phylum. Moreover, when analyzing the class level for each phylum, several differences between the samples were observed. Furthermore, lower proportions of Proteobacteria and Acidobacteria were observed in the soil sample under the influence of the bird's colony, which most probably could be linked to higher nitrogen concentrations in that sample.

The crucial role of seabirds in the enrichment of nutrient-poor polar terrestrial ecosystem is well-known. However, no studies have examined the potentially different impacts associated with piscivorous and planktivorous bird colonies on the surrounding tundra soils. Therefore, we compared guano deposition and physical and chemical parameters of soil near two large seabird colonies, one of planktivorous little auks (Alle alle) and the other comprising piscivorous Brunnich’s guillemots (Uria lomvia) and kittiwakes (Rissa tridactyla). The two colonies generated similar levels of guano deposition, with the intensity of deposition decreasing away from the colony. Guano deposition adjacent to both colonies was considerably higher than that in control areas. The increased guano supply around colonies significantly enhanced soil conductivity, nitrogen (NO3−, NH4+), potassium (K+), and phosphate (PO43−) ion concentrations and led to reduced pH values. Guano deposition explained 84 % (piscivorous colony) and 67 % (planktivorous colony) of the total variation in the tested soil parameters. Planktivore and piscivore colonies affected adjacent tundra in different ways. The phosphate content and pH value of soil influenced by piscivores were significantly higher than values measured in planktivore-influenced soil. The gradient of guano deposition and associated ion content in the soil decreased more rapidly with distance from the piscivore colony. Climate-induced changes in populations of planktivorous and piscivorous seabirds are expected in the study region and may therefore have substantial consequential effects on Arctic terrestrial ecosystems.

Kwasniewski, S., Gluchowska, M., Walkusz, W., Karnovsky, N. J., Jakubas, D., Wojczulanis-Jakubas, K., Harding, A. M. A., Goszczko, I., Cisek, M., Beszczynska-Möller, A., Walczowski, W., Weslawski, J. M., and Stempniewicz, L. 2012. Interannual changes in zooplankton on the West Spitsbergen Shelf in relation to hydrography and their consequences for the diet of planktivorous seabirds. – ICES Journal of Marine Science, 69: 890–901. The purpose of the work was to determine how atmospheric and oceanic processes (the North Atlantic Oscillation (NAO) and the Arctic Ocean Oscillation (AOO)) influence hydrography and zooplankton on the West Spitsbergen Shelf (WSS), and the impacts of the processes on chick meals of zooplanktivorous little auks Alle alle. There were distinct Atlantic and Arctic oceanographic domains on the shelf resulting from the presence of the West Spitsbergen Current and the Sørkapp Current, which contain different proportions of Calanus finmarchicus and C. glacialis. The abundance of warm- and cold-water species varied as a result of an interplay between processes in the atmosphere and ocean. In the Arctic domain, on which the study focused, the NAO impacted oceanography, zooplankton, and consequently little auk chick meals, with time-lags of 4–7 years. The diet of little auk chicks was more energy-rich when C. glacialis stage 5 in the Arctic community were more easily available. To date, the changes in zooplankton abundance on the WSS have not posed a threat to the ability of little auks to feed their chicks lipid-rich Arctic copepods.

Despite a widespread recognition of the role of seabird colonies in the fertilization of nutrient-poor polar terrestrial ecosystems, qualitative and quantitative data documenting any consequential influence on soil invertebrate communities are still lacking. Therefore, we studied community structure and abundance of springtails (Collembola) in ornithogenic tundra near two large seabird colonies in Hornsund, south-west Spitsbergen. We found considerably (5–20×) higher densities and biomass of Collembola in the vicinities of both colonies (the effect extending up to ca. 50 m from the colony edge) than in comparable control areas of tundra not influenced by allochtonous nutrient input. The most common springtails observed in the seabird-influenced areas were Folsomia quadrioculata, Hypogastrura viatica and Megaphorura arctica. The latter species appeared the most resistant to ornithogenic nutrient input and was found commonly closest to the bird colonies. Collembolan abundance decreased with increasing distance from the seabird colonies. However, relationships between collembolan density and specific physicochemical soil parameters and vegetation characteristics were weak. The most important factors were the cover of the nitrophilous green alga Prasiola crispa, total plant biomass and soil solution conductivity, all of which were correlated with distance from the colony and estimated amount by guano deposition. Community composition and abundance of springtails showed no evidence of being influenced of seabird diet, with no differences apparent between communities found in ornithogenic tundra developing in the vicinity of planktivorous and piscivorous seabird colonies. The study provides confirmation of the influence of marine nutrient input by seabirds on soil microfaunal communities.

In conditions of deteriorating food availability, seabirds may maximize their breeding success by increasing reproductive effort, which compromises body condition, stress level, survival, and future reproductive success. We studied a small planktivorous alcid, the little auk Alle alle, in 2 breeding colonies in west Spitsbergen, Norway (Hornsund and Magdalenefjorden) with contrast- ing oceanographic conditions (Arctic and Atlantic environments, respectively). We hypothesized that the chick diet composition and parental foraging effort differs between these colonies, which results in intercolony variation in body mass and stress level of both adults and chicks. We found dif- ferences in sea temperature and salinity (both lower in Hornsund) and the abundance of Atlantic copepod Calanus finmarchicus (3.6 times less abundant in Hornsund) between foraging areas. Birds from both colonies foraged selectively on Calanus glacialis CV. Composition, total biomass and energy content of food loads were similar in both colonies, though food delivered to nestlings in Mag- dalenefjorden was more diverse. The frequency of feeds was also similar in both colonies. Parent lit- tle auks in Magdalenefjorden, however, performed longer foraging trips than in Hornsund (medians 183 vs. 124 min). Longer foraging trips suggest that these birds traveled longer distances to find abundant prey at the marginal sea ice zone and/or spent more time foraging close to the colony but in poorer foraging areas. Despite increased parental efforts in Magdalenefjorden, body mass and stress levels of adults and chicks were similar in both colonies. This suggests that little auks from northwest Spitsbergen did not reach a threshold requiring prioritization of self-maintenance over chick provisioning.

Composition and abundance of zooplankton were studied simultaneously with feeding ecology of planktivorous Little Auks (Alle alle) in two different sea shelf areas of West Spitsbergen, Norway, in summer 2007. Zooplankton was collected adjacent to bird colonies in Magdalenefjorden (influenced by Atlantic West Spitsbergen Current) and Hornsund (dominated by the Arctic Sorkapp Current). In spite of different hydrological situations, the abundance of prey preferred by Little Auks, Arctic Calanus glacialis copepodids stage V, among zooplankton was similar in both localities. However, there was much more of Atlantic Calanus finmarchicus on the shelf outside Magdalenefjorden compared to Hornsund, resulting in different abundance ratios of Arctic to Atlantic copepods in the two areas (1:14 and 1:1, respectively). Even greater differences between the two areas occurred in the ratio of C. glacialis CV to other zooplankters, amounting to 1:40 in Magdalenefjorden and 1:6 in Hornsund. In both Little Auk colonies food brought by parents to their chicks contained mainly C. glacialis CV, albeit the proportion of this copepod in meals was significantly higher in Hornsund. Meals delivered to Little Auk chicks in Hornsund had also higher zooplankton numbers, biomass and energy content. In Magdalenefjorden, on the other hand, a higher number of feedings and longer duration of foraging trips were recorded. These differences became more apparent with increasing energy requirements of the fast growing nestlings. This was probably a consequence of lower relative abundance of the Little Auks’ preferred prey in the sea adjacent to Magdalenefjorden colony. It seems that searching for the preferred food items, such as C. glacialis, among abundant but less favored C. finmarchicus, may require more time and energy demanding foraging behavior. As a consequence, foraging effort of the Little Auk parents from Magdalenefjorden was higher, and feeding efficiency lower, than those of birds from Hornsund. Increasing influx of warm Atlantic waters that bring boreal zooplankton to the Arctic Seas may have negative impacts on Little Auks’ time and energy budgets and eventually on their breeding success and range of breeding distribution.

Solar radiation reflectance was analysed to characterize Arctic ornithogenic tun− dra developing in the vicinity of large breeding colony of Brunnich's guillemots Uria lomvia and kittiwakes Rissa tridactyla at the foot of Gnalberget cliff (Hornsund, SW Spitsbergen). Radiometric method was found to be a useful tool for studying structure and functioning of plant formations. We measured reflectance of four wavelengths: 554 nm (YG), 655 nm (RED), 870 nm (NIR) and 1650 nm (SWIR) at 10 plots situated along the transect running from the colony to the sea. Moreover, data of plant community character, species quantitative composition as well as total biomass were collected to relate these pa− rameters with the spectral values. The results showed that radiometric data characterized vegetation well enough to recognize the same plant communities on the basis of spectral reflectance as distinguished with traditional phytosociological methods.

Many arctic terrestrial ecosystems suffer from a permanent deficiency of nutrients. Marine birds that forage at sea and breed on land can transport organic matter from the sea to land, and thus help to initiate and sustain terrestrial ecosystems. This organic matter initiates the emergence of local tundra communities, increasing primary and secondary production and species diversity. Climate change will influence ocean circulation and the hydrologic regime, which will consequently lead to a restructuring of zooplankton communities between cold arctic waters, with a dominance of large zooplankton species, and Atlantic waters in which small species predominate. The dominance of large zooplankton favours plankton-eating seabirds, such as the little auk (Alle alle), while the presence of small zooplankton redirects the food chain to plankton-eating fish, up through to fish-eating birds (e.g., guillemots Uria sp.). Thus, in regions where the two water masses compete for dominance, such as in the Barents Sea, plankton-eating birds should dominate the avifauna in cold periods and recess in warmer periods, when fish-eaters should prevail. Therefore under future anthropogenic climate scenarios, there could be serious consequences for the structure and functioning of the terrestrial part of arctic ecosystems, due in part to changes in the arctic marine avifauna. Large colonies of plankton-eating little auks are located on mild mountain slopes, usually a few kilometres from the shore, whereas colonies of fish-eating guillemots are situated on rocky cliffs at the coast. The impact of guillemots on the terrestrial ecosystems is therefore much smaller than for little auks because of the rapid washing-out to sea of the guano deposited on the seabird cliffs. These characteristics of seabird nesting sites dramatically limit the range of occurrence of ornithogenic soils, and the accompanying flora and fauna, to locations where talus-breeding species occur. As a result of climate warming favoring the increase of ichthyiofagous cliffnesting seabirds, we can expect that large areas of ornithogenic tundra around the colonies of plankton-eating seabirds situated far from the sea may disappear, while areas of tundra in the vicinity of cliffs inhabited by fish-eating seabirds, with low total production and supporting few large herbivores, will likely increase, but only imperceptibly. This may lead to habitat fragmentation with negative consequences for populations of tundra-dependent birds and mammals, and the possibility of a substantial decrease in biodiversity of tundra plant and animal communities. r 2007 Elsevier Ltd. All rights reserved.

At least 10,000 Puffins Fratercula arctica are taken annually at the Nólsoy colony by fowling. This figure probably exceeds the recruitment rate and may cause gradual decrease of the colony size. Continuous decline (since 1900) of the number of breeding birds as well as shrinking of the colony area suggest long-lasting overexploitation. The collapse of the local population is probably delayed only by immigration of immature Puffins from the large Icelandic population. We recovered 37 (20.1%) of 184 Puffin fledglings ringed in 1997 at Nólsoy colony. All rings originated from birds caught by fowlers operating on Nólsoy (34 birds) and on other Faeroe islands (3 birds). First Puffins were fowled at colony in 1999, 54% in 2000 (3 yrs old), and the last bird in 2003 as 6 yrs old. Puffins which had been harvested, i.e. those which survived at least 2 years, were on average larger and heavier at fledging than the rest of the ringed chicks. Most of them originated from early broods. Our data suggest that adult Puffins breeding earlier produce better quality offspring that survive in higher proportion.

Seabirds are among the most important vectors transferring biogenic compounds from the sea onto land in the polar regions and, consequently, influencing the properties of soil and vegetation. We studied the influence of bird colonies (Adelie penguin Pygoscelis adeliae, gentoo penguin P. papua and giant petrels Macronectes giganteus) on soil properties and plant communities on King George Island, Maritime Antarctic. We designated seven transects, each starting from the colony edge and running to a natural boundary feature, which were divided into contiguous sample plots where we identified specific plant taxa (Prasiola crispa, Deschampsia antarctica, Colobanthus quitensis, Usnea sp.), as well as hydrophilous and xerophilous ecological groups of mosses. Based on percentage contributions of each of these taxa, we distinguished six distinct vegetation zones along the transects, in which we measured physical (moisture, conductivity and pH) and chemical (NO3 −, NO2 −, NH4 +, K+ and PO4 3− content) soil parameters. Our study confirmed that, with increasing distance from bird colonies, the concentration of nutrients and soil conductivity decreased, while pH increased. The vegetation zones were clearly related to this gradient of seabird colony influence and occurred in the same sequence for all three bird species examined, although the largest colony of Adelie penguins had the strongest effect on vegetation. Similarly, the physical and chemical soil properties did not differ significantly between the colonies.

The impact of Glaucous Gull (Larus hyperboreus) predation on the Little Auk (Alle alle) during breeding season at the Ariekammen slopes in Hornsund was compared between 1983 and 2003-04. During the nestling period, gulls killed more young Little Auks in 1983 than in 2003. During the period of the colony departure in 2003, there were more Glaucous Gulls present and they killed more Little Auks than 20 years previous. Changes were found in the strategy of the colony departure by the Little Auk. In 2004, the rate of fledglings departed from the colony during “day” hours was higher than in 1983 and a higher proportion of fledglings left the colony escorted by more than one adult bird. This could be a consequence of general increase in the Glaucous Gull numbers or a year-to-year fluctuation and needs further investigations.

An unusually small Atlantic Puffin fledging Fratercula arctica was found on Nólsoy, Faeroe Islands, in August 1997. The bird was fully feathered with no down remnants and left the colony during the peak of the fledging period. Some of its measurements (those where feather length is crucial, such as wing and tail) fell within the range of minimal values found in young puffins fledging prematurely. Others, like bill and tarsus lengths with a prevailing skeletal component, were less than the lowest known values. Very small body size seems to account for the very low body mass of the bird. However, proportionally developed pectoral muscles as well as the bird's overall good appearance (fully feathered with no down) and behaviour indicated that it apparently was not food stressed or starving.

The feeding ecology of the Long-tailed Duck Clangula hyemalis was studied in the Gulf of Gdańsk during eight wintering seasons (November–April) 1972–1976 and 1986–1990 (423 food samples). The number of food taxa consumed was at least 28 (23 animal and 5 plant). Long-tailed Ducks fed mainly on bivalves of which Macoma baltica and Mya arenaria were the most important, then Mytilus edulis and Cardium glaucum. Fish, mostly Ammodytidae, and fish eggs were present in ca. every fourth sample. Crustaceans, polychaetes and gastropods constituted the remaining significant prey. Plant food was incidental. Birds selected main food items (3 bivalves) of shell length ca. 11.0–11.6 mm regardless of their different average size found in zoobenthos. Seasonal and some age and sex related differences in Long-tailed Duck diet were found. They consumed proportionally more Mytilus and Cardium in December and January and less later in the season. Crustaceans, polychaetes and especially fish (fish eggs) increased their percent share in the diet in the spring. Adult birds tended to eat more Mytilus and Cardium while immatures ingested more crustaceans. Birds caught in nets set deep (>20 m) fed largely on Mesidothea entomon. Long-tailed Ducks function as first to fourth-order carnivores in the food web of the Gulf of Gdansk. Due to their high numbers and long period of staying they consume considerable biomass of main food prey. Estimated yearly consumption of bivalves amounts to 6 350 tonnes (Macoma baltica–2,100, Mya arenaria–1,700, Mytilus edulis–1,600, Cardium glaucum–950), fish–1,120, crustaceans–400, polychaetes–200, and gastropods–125 tonnes. At least locally, they prey significantly on certain age classes of the most important food taxa.

We studied the relative importance of several environmental factors for tundra plant communities in five locations across Svalbard (High Arctic) that differed in geographical location, oceanographic and climatic influence, and soil characteristics. The amount of marine-derived nitrogen in the soil supplied by seabirds was locally the most important of the studied environmental factors influencing the tundra plant community. We found a strong positive correlation between δ15N isotopic values and total N content in the soil, confirming the fundamental role of marine-derived matter to the generally nutrient-poor Arctic tundra ecosystem. We also recorded a strong correlation between the δ15N values of soil and of the tissues of vascular plants and mosses, but not of lichens. The relationship between soil δ15N values and vascular plant cover was linear. In the case of mosses, the percentage ground cover reached maximum around a soil δ 15N value of 8‰, as did plant community diversity. This soil δ15N value clearly separated the occurrence of plants with low nitrogen tolerance (e.g. Salix polaris) from those predominating on high N content soils (e.g. Cerastium arcticum, Poa alpina). Large colonies of planktivorous little auks have a great influence on Arctic tundra vegetation, either through enhancing plant abundance or in shaping plant community composition at a local scale.

Food samples from 102 seabirds from eight species (fulmar Fulmarus glacialis, common eider Somateria mollissima, glaucous gull Larus hyperboreus, kittiwake Rissa tridaayla, arctic tern Sterna paradisaea, Briinnich's guillemot Uria lorn via, black guillemot Cepphus grylle, little auk Alle alle) were collected during the period August 1991–1993 in the southern part of the Frans Josef Land archipelago, 80°N, 53°E. The pelagic amphipod Parathemisto libellula and polar cod Boreogadus saida were the two most commonly taken food items (frequency of occurrence over 50% and weight contribution more than 70%). Ice-associated crustaceans contributed to some 10% of the weight in the samples. In general, the food composition was very similar to that reported from Svalbard. However, birds from Frans Josef Land fed on a lower diversity of prey compared to Svalbard populations.