Uria Aalge Research Articles

Later at higher latitudes: large‐scale variability in seabird breeding timing and synchronicity

AbstractIn seasonal environments, organisms are expected to optimally schedule reproduction within an annual range of environmental conditions. Latitudinal gradients generate a range of seasonality to which we can expect adaptations to have evolved, and can be used to explore drivers of timing strategies across species’ distribution ranges. This study compares the timing of egg hatching in four seabird species (Atlantic puffin Fratercula arctica, black‐legged kittiwake Rissa tridactyla, common guillemot Uria aalge, and Brünnich's guillemot U. lomvia) covering a subarctic to Arctic latitudinal gradient along the Norwegian coast to Svalbard (65–79°N). Hatching was significantly delayed by an estimated 1.7, 2.3, and 1.9 d per latitudinal degree for puffins, kittiwakes, and common guillemots, respectively, but was not delayed for Brünnich's guillemots. Hatching distributions revealed an increase in intra‐annual breeding synchronicity along a latitudinal gradient for kittiwakes only, whereas the two guillemots exhibited high hatching synchronicity at all colonies. We used this large‐scale, multispecies timing data series to discuss constraints, adaptations, and mechanisms affecting breeding timing, a necessary step to recognize risks to populations and predict future ecosystem change.

Foraging segregation of two congeneric diving seabird species breeding on St. George Island, Bering Sea

Abstract. Subarctic environmental changes are expected to affect the foraging ecology of marine top predators, but the response to such changes may vary among species if they use food resources differently. We examined the characteristics of foraging behavior of two sympatric congeneric diving seabird: common (Uria aalge: hereafter COMUs) and thick-billed (U. lomvia: hereafter TBMUs) murres breeding on St. George Island, located in the seasonal sea-ice region of the Bering Sea. We investigated their foraging trip and flight durations, diel patterns of dive depth, and underwater wing strokes, along with wing morphology and blood stable isotope signatures and stress hormones. Acceleration–temperature–depth loggers were attached to chick-guarding birds, and data were obtained from 7 COMUs and 12 TBMUs. Both species showed similar mean trip duration (13.2 h for COMUs and 10.5 h for TBMUs) and similar diurnal patterns of diving (frequent dives to various depths in the daytime and less frequent dives to shallow depths in the nighttime). During the daytime, the dive depths of COMUs had two peaks in shallow (18.1 m) and deep (74.2 m) depths, while those of TBMUs were 20.2 m and 59.7 m. COMUs showed more frequent wing strokes during the bottom phase of dives (1.90 s−1) than TBMUs (1.66 s−1). Fish occurred more frequently in the bill loads of COMUs (85 %) than those of TBMUs (56 %). The δ15N value of blood was significantly higher in COMUs (14.5 ‰) than in TBMUs (13.1 ‰). The relatively small wing area (0.053 m2) of COMUs compared to TBMUs (0.067 m2) may facilitate their increased agility while foraging and allow them to capture more mobile prey such as larger fishes that inhabit deeper depths. These differences in food resource use may lead to the differential responses of the two murre species to marine environmental changes in the Bering Sea.

Impacts of oil spills on seabirds: Unsustainable impacts of non-renewable energy

Accidental spillage of oil in to the sea from shipping transport and drilling rigs results in spills that cause significant unsustainable mortality of wildlife and destroys marine ecosystem services. External oiling of seabirds causes large scale mortality within days following a spill, while survivors suffercauses long term chronic effects from the exposure to toxic polycyclic aromatic hydrocarbons (PAHs) present in ingested oil. Survival rates for rehabilitated oiled birds are very low despite investment of significant resources. PAHs disturb thyroid homeostasis which plays a vital role in the control of energy metabolism. In this study, plasma PAH and thyroid-stimulating hormone (TSH) were quantified as biomarkers of exposure and endocrine disruption in oiled guillemots (Uria aalge). Mean plasma PAH and TSH concentrations, were 98.1 ± 8.3 ng/ml and 0.13 ± 0.02 ng/ml and these parameters were found to be negatively correlated (p < 0.01) indicative of PAH-associated thyroid hormone suppression in more heavily oiled birds. Body condition and weight were also lower in birds that died compared with birds that were released. The data also show the value of measuring plasma TSH and PAH to monitor metabolic status and progress of decontamination of oiled birds in a rehabilitation setting.

Diet Changes in Breeding Herring Gulls (Larus argentatus) in Witless Bay, Newfoundland and Labrador, Canada, over 40 Years

Abstract. The diets of gulls (Laridae) can have consequences for reproductive success, chick growth, and survival, yet there have been no quantitative assessments in eastern Newfoundland since the early 1970s. The diet of Herring Gulls (Larus argentatus) was examined through regurgitated prey items and pellets on Gull Island, Witless Bay, Newfoundland and Labrador, Canada, in 2012, and compared with similar data from 1970–1971. There was a significant shift in Herring Gull diet composition from blue mussels (Mytilus edulis) and capelin (Mallotus villosus) in the 1970s to garbage and Common Murre (Uria aalge) eggs in 2012. Delays in capelin spawning and the large increase in breeding Common Murres on Gull Island are likely factors influencing Herring Gull diet. Garbage, which includes human food scraps as well as plastic debris, now constitutes the single largest diet item for Herring Gulls, corresponding with a global increase in plastic pollution. The consistently low contribution of fisheries discards s...

Quantifying pursuit‐diving seabirds’ associations with fine‐scale physical features in tidal stream environments

Summary The rapid increase in the number of tidal stream turbine arrays will create novel and unprecedented levels of anthropogenic activity within habitats characterized by horizontal current speeds exceeding 2 ms−1. However, the potential impacts on pursuit‐diving seabirds exploiting these tidal stream environments remain largely unknown. Identifying similarities between the fine‐scale physical features (100s of metres) suitable for array installations, and those associated with foraging pursuit‐diving seabirds, could identify which species are most vulnerable to either collisions with moving components, or displacement from these installations. A combination of vessel‐based observational surveys, Finite Volume Community Ocean Model outputs and hydroacoustic seabed surveys provided concurrent measures of foraging distributions and physical characteristics at a fine temporal (15 min) and spatial (500 m) resolution across a tidal stream environment suitable for array installations, during both breeding and non‐breeding seasons. These data sets were then used to test for associations between foraging pursuit‐diving seabirds (Atlantic puffins Fratercula arctica, black guillemots Cepphus grylle, common guillemots Uria aalge, European shags Phalacrocorax aristotelis) and physical features. These species were associated with areas of fast horizontal currents, slow horizontal currents, high turbulence, downward vertical currents and also hard–rough seabeds. The identity and strength of associations differed among species, and also within species between seasons, indicative of interspecific and intraspecific variations in habitat use. However, Atlantic puffins were associated particularly strongly with areas of fast horizontal currents during breeding seasons, and European shags with areas of rough–hard seabeds and downward vertical currents during non‐breeding seasons. Synthesis and applications. Atlantic puffins’ strong association with fast horizontal current speeds indicates that they are particularly likely to interact with installations during breeding seasons. Any post‐installation monitoring and mitigation measures should therefore focus on this species and season. The multi‐species associations with high turbulence and downward vertical currents, which often coincide with fast horizontal current speeds, also highlight useful pre‐installation mitigation measures via the omission of devices from these areas, reducing the overall likelihood of interactions. Environmental impact assessments (EIA) generally involve once‐a‐month surveys across 2‐year periods. However, the approaches used in this study show that more focussed surveys can greatly benefit management strategies aiming to reduce the likelihood of negative impacts by facilitating the development of targeted mitigation measures. It is therefore recommended that these approaches contribute towards EIA within development sites.

Food sources of wintering piscivorous waterbirds in coastal waters: A triple stable isotope approach for the southeastern Baltic Sea

This study uses a triple isotope approach (δ13C, δ15N, and δ34S) to quantify the main food sources for wintering piscivorous waterbirds in the coastal zone of the southeastern Baltic Sea. Significant differences of δ15N and δ34S values among pelagic fishes, benthic fishes, and benthopelagic European smelt (Osmerus eperlanus) were detected, while δ13C was similar among these sources. Using different combinations of δ13C, δ15N, and δ34S values in mixing models, we found that common guillemot (Uria aalge) and red-throated diver (Gavia stellata) mostly foraged on pelagic prey (50–70% and 51–56%, respectively), whereas great crested grebe (Podiceps cristatus) consumed benthic prey (48–53%). European smelt comprised a substantial proportion of the diet of studied birds (19–36%). A stable isotope approach can be recommended as a non-lethal method to study avian diets in the coastal waters of the Baltic Sea.

The use of an unsupervised learning approach for characterizing latent behaviors in accelerometer data.

The recent increase in data accuracy from high resolution accelerometers offers substantial potential for improved understanding and prediction of animal movements. However, current approaches used for analysing these multivariable datasets typically require existing knowledge of the behaviors of the animals to inform the behavioral classification process. These methods are thus not well-suited for the many cases where limited knowledge of the different behaviors performed exist. Here, we introduce the use of an unsupervised learning algorithm. To illustrate the method's capability we analyse data collected using a combination of GPS and Accelerometers on two seabird species: razorbills (Alca torda) and common guillemots (Uria aalge). We applied the unsupervised learning algorithm Expectation Maximization to characterize latent behavioral states both above and below water at both individual and group level. The application of this flexible approach yielded significant new insights into the foraging strategies of the two study species, both above and below the surface of the water. In addition to general behavioral modes such as flying, floating, as well as descending and ascending phases within the water column, this approach allowed an exploration of previously unstudied and important behaviors such as searching and prey chasing/capture events. We propose that this unsupervised learning approach provides an ideal tool for the systematic analysis of such complex multivariable movement data that are increasingly being obtained with accelerometer tags across species. In particular, we recommend its application in cases where we have limited current knowledge of the behaviors performed and existing supervised learning approaches may have limited utility.

Paradise lost already? A naturalist interpretation of the pelagic avian and marine mammal detection database of the IceAGE cruise off Iceland and Faroe Islands in fall 2011

We present naturalist sightings of seabirds and marine mammals made during a research cruise with the IceAGE project off Iceland and the Faroe Islands during September 2011. Our findings from the obtained pelagic database are in-line with many other, more in-depth studies, showing major declines for pelagic seabirds and likely sea mammals, thus revising the role that Iceland now plays for such species. Northern Fulmar (Fulmarus glacialis) was the most recorded species, followed by different gulls, Black-legged Kittiwake (Rissa tridactyla) and Northern Gannet (Morus bassanus). However, Atlantic Puffin (Fratercula arctica) and Common Murre (Uria aalge) were only seen very rarely, and no observations were made of Dovekie (Alle alle) or Thick-billed Murre (U. lomvia). These observations were surprising since Iceland is known, so far, to host globally relevant populations of these auk species. A surprising high number of thirteen species of passerines were also detected offshore, mostly Wheatear (Oenanthe oenanthe), Meadow Pipit (Anthus pratensis) and Reed Bunting (Emberiza schoeniclus). Only a few marine mammals (Balaenoptera and Megaptera sp.) were encountered. Our detections present underestimates but are discussed in relation to ongoing and recently reported but dramatic anthropogenic changes of Iceland and in the North Atlantic overall. These include the substantial decrease in bird populations, overfishing and subsequent trophic cascades, as well as climate change, Arctic shipping and more industrial development to come. In light of these dramatic ecological changes, we conclude with an urgent request for an improved effective conservation management for Iceland, the North Atlantic and its stakeholders for directly related global governance to handle problems proactively.

Assessing the Role of Seabirds in the Ecology of Influenza A Viruses.

Wild waterbirds, specifically waterfowl, gulls, and shorebirds, are recognized as the primordial reservoir of influenza A viruses (IAVs). However, the role of seabirds, an abundant, diverse, and globally distributed group of birds, in the perpetuation and transmission of IAVs is less clear. Here we summarize published and publicly available data for influenza viruses in seabirds, which for the purposes of this study are defined as birds that exhibit a largely or exclusively pelagic lifestyle and exclude waterfowl, gulls, and shorebirds, and we review this collective dataset to assess the role of seabirds in the influenza A ecology. Since 1961, more than 40,000 samples have been collected worldwide from the seabirds considered here and screened, using a variety of techniques, for evidence of active or past IAV infection. From these data, the overall prevalence of active infection has been estimated to be very low; however, serological data provide evidence that some seabird species are more frequently exposed to IAVs. Sequence data for viruses from seabirds are limited, except for murres (common murre, Uria aalge, and thick-billed murre, Uria lomvia; family Alcidae) for which there are full or partial genome sequences available for more than 80 viruses. Characterization of these viruses suggests that murres are infected with Group 1 hemagglutinin subtype viruses more frequently as compared to Group 2 and also indicates that these northern, circumpolar birds are frequently infected by intercontinental reassortant viruses. Greater temporal and spatial sampling and characterization of additional viruses are required to better understand the role of seabirds in global IAV dynamics.

Seasonal Variation in Parental Care Drives Sex-Specific Foraging by a Monomorphic Seabird.

Evidence of sex-specific foraging in monomorphic seabirds is increasing though the underlying mechanisms remain poorly understood. We investigate differential parental care as a mechanism for sex-specific foraging in monomorphic Common Murres (Uria aalge), where the male parent alone provisions the chick after colony departure. Using a combination of geolocation-immersion loggers and stable isotopes, we assess two hypotheses: the reproductive role specialization hypothesis and the energetic constraint hypothesis. We compare the foraging behavior of females (n = 15) and males (n = 9) during bi-parental at the colony, post-fledging male-only parental care and winter when parental care is absent. As predicted by the reproductive role specialization hypothesis, we found evidence of sex-specific foraging during post-fledging only, the stage with the greatest divergence in parental care roles. Single-parenting males spent almost twice as much time diving per day and foraged at lower quality prey patches relative to independent females. This implies a potential energetic constraint for males during the estimated 62.8 ± 8.9 days of offspring dependence at sea. Contrary to the predictions of the energetic constraint hypothesis, we found no evidence of sex-specific foraging during biparental care, suggesting that male parents did not forage for their own benefit before colony departure in anticipation of post-fledging energy constraints. We hypothesize that unpredictable prey conditions at Newfoundland colonies in recent years may limit male parental ability to allocate additional time and energy to self-feeding during biparental care, without compromising chick survival. Our findings support differential parental care as a mechanism for sex-specific foraging in monomorphic murres, and highlight the need to consider ecological context in the interpretation of sex-specific foraging behavior.

The functional morphology of the jaw apparatus in the black guillemot (Cepphus grylle) and the thick-billed (Uria lomvia) and common (Uria aalge) murres

The jaw muscles of the thick-billed murre have been described in detail and depicted with comparative notes on the jaw muscles in the common murre and the black guillemot. Owing to adaptation to underwater hunting of mobile prey (first of all, small fish), the composition of the dorsal adductor muscles in the studied species has become simplified in part, compared with their ancestral form, and has become similar to that of another underwater fisher, the great crested grebe (Podiceps cristatus). The attachment of the superficial portion of the external adductor muscle to the postorbital projection was strengthened, especially in both murres. In the external layer of the medial portion of the adductor, the muscle fibers gained secondary insertion by the horizontal aponeurosis, similarly to those of the superficial portion, thus increasing the horizontal (retracting) force component, which lowers the long upper jaw. The caudal part of the deep portion of the external adductor became incorporated in the medial portion, but in the murres, especially in the thickbilled murre, part of it is similar to the posterior adductor, which enhances the retracting force as well. All three species show traces of a transfer of the muscle fascicle from the superficial pseudotemporal muscle to the deep pseudotemporal muscle, giving the same effect. Confirmation of the relatively separated position of the guillemot and of its generalized morphological state were found. The specific features of the murres’ adaptation to fishing, including morphofunctional prerequisites for forage segregation of the two murre species, are understandable as the basis of their sympatric existence.

Approaching population thresholds in presence of uncertainty: Assessing displacement of seabirds from offshore wind farms

Assessment of the displacement impacts of offshore wind farms on seabirds is impeded by a lack of evidence regarding species-specific reactions to developed sites and the potential ecological consequences faced by displaced individuals. In this study, we present a method that makes best use of the currently limited understanding of displacement impacts. The combination of a matrix table displaying the full range of potential displacement and mortality levels together with seasonal potential biological removal (PBR) assessments provides a tool that increases confidence in the conclusions of impact assessments. If unrealistic displacement levels and/or mortality rates are required to equal or approach seasonal PBRs, this gives an indication of the likeliness of adverse impacts on the assessed population. This approach is demonstrated by assessing the displacement impacts of an offshore wind farm cluster in the German North Sea on the local common guillemot (Uria aalge) population.

Effects of Prenatal Environment on Phenotype Are Revealed by Postnatal Challenges: Embryonic Hormone Exposure, Adrenocortical Function, and Food in Seabird Chicks.

The interaction between prenatal environments and postnatal environments is an important source of phenotypic variability. We examined the ability of prenatal steroid exposure and postnatal energy restriction to explain adrenocortical function and fledging age in captive seabird chicks. We proposed and tested two hypotheses: (1) the strength of prenatal effects is attenuated by challenging postnatal environments (postnatal override) and (2) the strength of prenatal effects increases with the severity of postnatal challenges (postnatal reveal). We reared common murre (Uria aalge) chicks and measured prenatal exposure to corticosterone (CORT) and testosterone (T) from allantoic waste. Adrenocortical function was assessed after 10 d of ad lib. feeding and then after 5 and 10 d on controlled diets. Postnatal override predicts that prenatal steroids will explain more phenotypic variation before implementation of energy restriction; postnatal reveal predicts that the contribution of prenatal steroids will increase with duration and severity of energy restriction. Energy restriction increased secretion of baseline CORT and the adrenocortical response to the standardized stressor of handling and restraint. The ability of prenatal steroids to explain baseline CORT increased with duration of energy restriction, and for day 20 free baseline CORT, there was a significant interaction between kilojoules per day and prenatal CORT levels; severity of restriction strengthened the relationship between prenatal hormone levels and postnatal hormone levels. Both maximum CORT at day 20 and fledging age were best explained by diet treatment and day 15 or day 20 baseline CORT, respectively. Overall, prenatal CORT increased fledging age and baseline secretion of CORT, while prenatal T decreased them. However, prenatal effects on adrenocortical function were apparent only under the energy restriction conditions. Thus, we found some support for the postnatal reveal hypothesis; our results suggest that some prenatal effects on phenotype may be more likely to manifest in challenging postnatal environments.

The visual fields of Common Guillemots Uria aalge and Atlantic Puffins Fratercula arctica: foraging, vigilance and collision vulnerability

Significant differences in avian visual fields are found between closely related species that differ in their foraging technique. We report marked differences in the visual fields of two auk species. In air, Common Guillemots Uria aalge have relatively narrow binocular fields typical of those found in non‐passerine predatory birds. Atlantic Puffins Fratercula arctica have much broader binocular fields similar to those that have hitherto been recorded in passerines and in a penguin. In water, visual fields narrow considerably and binocularity in the direction of the bill is probably abolished in both auk species. Although perceptual challenges associated with foraging are similar in both species during the breeding season, when they are piscivorous, Puffins (but not Guillemots) face more exacting perceptual challenges when foraging at other times, when they take a high proportion of small invertebrate prey. Capturing this prey probably requires more accurate, visually guided bill placement and we argue that this is met by the Puffin's broader binocular field, which is retained upon immersion; its upward orientation may enable prey to be seen in silhouette. These visual field configurations have potentially important consequences that render these birds vulnerable to collision with human artefacts underwater, but not in air. They also have consequences for vigilance behaviour.

Seventeenth census of seabird populations in the sanctuaries of the North Shore of the Gulf of St. Lawrence, 2010

Seabirds in the 10 migratory bird sanctuaries of the North Shore of the Gulf of St. Lawrence, Quebec, Canada, which were created in 1925, have been censused regularly for the last 85 years. The sanctuaries support 16 seabird species, many of which are found in significant numbers. From 2005 to 2010, some notable population changes were observed: large increases in Common Murres (Uria aalge), Razorbills (Alca torda), and two species of cormorants and continuing declines in Black-legged Kittiwakes (Rissa tridactyla) and Atlantic Puffins (Fratercula arctica). The status of Leach’s Storm-Petrel (Oceanodroma leucorhoa) and Caspian Tern (Hydroprogne caspia) is extremely precarious because of their small breeding populations. Between 2005 and 2010, seabird numbers in the sanctuaries increased 19% overall and were stable in most sanctuaries (≤ 15% change); however, notable increases were observed at Îles Sainte-Marie (60%), Baie des Loups (47%), and Île à la Brume (44%). Nonetheless, considering historical records, increased surveillance and raising of awareness of seabird conservation in local communities near the sanctuaries of Île à la Brume, Baie des Loups, and Saint-Augustin would be most beneficial.

Effects of an extreme weather event on seabird breeding success at a North Sea colony

Quantifying the effects of extreme weather is a critical question in population ecology since climate models predict increased climate variability. Effects will vary among and within species due to exposure or susceptibility, yet few studies have considered these sources of variation simultaneously. We investigated the effects of a summer storm on the breeding success of 4 seabird species at a North Sea colony in relation to aspect, height above sea-level, distance to cliff edge and laying date. The storm lasted 8 h with gusts of >60 m s−1. In exposed plots, razorbills Alca torda had higher failure rates (28.5%) than European shags Phalacrocorax aristotelis (15.1%), black-legged kittiwakes Rissa tridactyla (15.6%) and common guillemots Uria aalge (10.4%). Conversely, failure rates in sheltered plots were negligible (shags 0.0%; kittiwakes 1.9%; no guillemot or razorbill plots in sheltered locations). Guillemots breeding closer to sea-level were more likely to fail, but cliff edge proximity did not affect failure rate. In razorbills, pairs that laid early were more likely to survive the storm. In all species, some failed pairs re-laid, and success of re-lays was lower than that of pairs that survived. Thus, re-laying only provided partial compensation, and, overall, the storm caused a net reduction in annual population production of 4.6, 10.7, 8.9 and 22.8% for shags, kittiwakes, guillemots and razorbills, respectively. Increased storm frequency may therefore have important consequences on seabird populations, but orientation of storms relative to colonies and timing in relation to the breeding season are likely to be critical in determining the overall effect.

Forage species in predator diets: Synthesis of data from the California Current

Characterization of the diets of upper-trophic pelagic predators that consume forage species is a key ingredient in the development of ecosystem-based fishery management plans, conservation of marine predators, and ecological and economic modeling of trophic interactions. Here we present the California Current Predator Diet Database (CCPDD) for the California Current region of the Pacific Ocean over the past century, assimilating over 190 published records of predator food habits for over 100 predator species and 32 categories of forage taxa (species or groups of similar species). Literature searches targeted all predators that consumed forage species: seabirds, cetaceans, pinnipeds, bony and cartilaginous fishes, and a predatory invertebrate. Diet data were compiled into a relational database. Analysis of the CCPDD highlighted differences in predator diet data availability based on geography, time period and predator taxonomy, as well as prominent prey categories. The top 5 forage taxa with the most predators included juvenile rockfish, northern anchovy, euphausiid krill, Pacific herring and market squid. Predator species with abundant data included Pacific hake, common murre, and California sea lion. Most diet data were collected during the summer; the lack of winter data will restrict future use of the CCPDD to understand seasonal patterns in predator diet unless more such data become available. Increased synthesis of historical information can provide new resources to understand patterns in the role of forage species in predator diet. Increased publication and/or accessibility of long-term datasets and data-sharing will further foster the synthesis of information intended to inform the management, conservation and understanding of marine food webs.

Relative importance of local enhancement as a search strategy for breeding seabirds: an experimental approach

During the breeding season, seabirds may use many behavioural strategies to reduce the time and energy spent searching for patchily distributed prey. Seabirds breeding at a large colony on the northeast Newfoundland coast (Funk Island), primarily common murres, Uria aalge, and northern gannets, Morus bassanus, predominantly feed on capelin, Mallotus villosus. Within foraging ranges, high-abundance capelin aggregations can be predictably located at deep-water (<40 m) spawning sites during the spawning period in mid- to late July, before which capelin are distributed in small, ephemeral schools. To investigate the 'local enhancement' hypothesis, we conducted a field-based experiment by deploying seabird-mimicking plastic models, or 'decoys', during JulyeAugust in 2009 and 2013, to determine whether breeding murres, gannets and Atlantic puffins, Fratercula arctica, respond to seabird aggregations. We used three decoy treatments: ‘Murre’, ‘Gannet’ and ‘Hotspot’ (both murre and gannet decoys). Pursuit-diving and plunge-diving birds were 4e7 and 17 times, respectively more likely to respond to decoy treatment relative to control periods. All species responded more to conspecifics, or to species within the same foraging guild, during single-species treatments (i.e. Murre, Gannet), but responded similarly (i.e. murres, puffins) or more (i.e. gannets) to the Hotspot treatment, suggesting that predator density in general is an important cue. Fewer murres responded to decoys during capelin spawning relative to pre-spawning, suggesting that murres use local enhancement to a lesser degree when prey can be predictably located nearby. This study provides experimental evidence that seabirds use local enhancement as a search strategy, but to varying degrees under changing prey conditions.

Monitoring of contaminants and their effects on the common Guillemot and the White-tailed sea eagle

Monitoring of contaminants and their effects on the common Guillemot and the White-tailed sea eagle

Ecological segregation among Thick-billed Murres (Urialomvia) and Common Murres (Uriaaalge) in the Northwest Atlantic persists through the nonbreeding season

To study the influence of inter- and intra-specific interactions on patterns of ecological segregation in nonbreeding habitat, we used geolocators to track year-round movements of congeneric and partially sympatric Thick-billed Murres (Uria lomvia (L., 1758)) and Common Murres (Uria aalge (Pontoppidan, 1763)) from seven Canadian colonies during 2007–2011. Locations from 142 individuals were (i) examined for species- and colony-specific spatiotemporal patterns, (ii) mapped with environmental data, and (iii) used to delineate core wintering areas. Compared with Common Murres, Thick-billed Murres dispersed across a wider range of latitudes and environments, had larger winter ranges, and showed greater variation in seasonal timing of movements. These interspecific differences were consistent at two scales: among colonies spanning a wide latitudinal range and at a sympatric colony. Intraspecifically, nonbreeding ecological segregation was more pronounced among colonies of Thick-billed Murres than of Common Murres: colonies of Thick-billed Murres tended to follow distinct movement patterns and segregate by latitude, whereas colonies of Common Murres segregated very little; moreover, the extent of segregation was more variable among Thick-billed Murres than Common Murres. For Thick-billed Murres, rather than complete divergence of winter ecological niche from Common Murres, we found a “widening” of an overlapping niche. This strategy of increased movement flexibility may enable Thick-billed Murres to mitigate competition both intra- and inter-specifically; we propose this movement strategy may have played a role in species divergence.