Murre Species Research Articles

The Designated Shipping Avoidance Area Around St. Lawrence Island, Northern Bering Sea, Is not Sufficient to Protect Foraging Habitat of the Island’s Breeding Seabird Community

One direct consequence of Arctic warming is the expansion of navigable portions of the Arctic Ocean. As a result, vessel traffic and the accompanying threats of spills, strikes and disturbance is intensifying throughout the Arctic. In the Bering Sea, these threats to the environment, wildlife and to the people who rely on marine resources for food and cultural continuity, are acute. We examined the spatial relevance of an Area To Be Avoided (ATBA), a shipping-risk mitigation measure, established around St. Lawrence Island with respect to seabirds, as sentinel species, habitat use. We studied four seabird species (common murre Uria aalge, thick-billed murre U. lomvia, crested auklet Aethia cristatella, black-legged kittiwake Rissa tridactyla) breeding at St. Lawrence Island in the northern Bering Sea. GPS tracking data from 47 at-sea foraging trips showed that both murre species and crested auklets distributed outside the ATBA, during at least one stage of the breeding season. A larger dataset based on the birds’ red blood cell isotopic signatures confirmed that for murres, the tracked individuals covered the broad niche exploited by these species. Habitat modelling further showed that the birds’ most suitable marine habitats were associated with seasonal surface chlorophyll blooms, and largely extended beyond the ATBA on the shelf north of the island. Data on the murres’ diet and diving behavior emphasized the importance of the shelf as a foraging habitat for these birds. We suggest that extending the ATBA to the north by only 35 km, would include areas of maximal habitat suitability. This extension would better protect seabirds, their foraging habitats and the cultural continuity of St. Lawrence Islanders, against growing threats stemming from Arctic warming.

Breeding together, wintering an ocean apart: Foraging ecology of the northern Bering Sea thick-billed and common murres in years of contrasting sea-ice conditions

Assessing impacts of environmental change on Arctic-breeding seabirds requires a better understanding of their year-round movement and foraging ecology. Here we examined the post-breeding movements and diving behavior of thick-billed (Uria lomvia) and common murres (U. aalge) breeding on St. Lawrence Island, northern Bering Sea, by using geolocators deployed in 2016 (n = 3, per species). During 2016–2019, we examined foraging niches and exposure to nutritional stress by using stable isotope signatures and corticosterone titers of blood and feather tissues (n = 60–96, per species). We found that thick-billed murres migrated to the Chukchi Sea in the fall and wintered in the western North Pacific, whereas common murres stayed in the eastern Bering Sea in the fall and wintered in the eastern North Pacific. Nutritional stress levels of breeding common murres were higher in 2017–2019, the period of historic low winter sea-ice extent, than in 2016. Higher nutritional stress levels of post-breeding thick-billed murres were associated with lower fall sea-ice extent in the Chukchi Sea. These results indicate that the loss of sea-ice might negatively affect murres breeding in the Pacific Arctic. Divergent migratory connectivity between the two murre species might also lead to different conservation threats both inside and outside the Arctic.

Between-year comparison of interactions between environmental parameters and various plankton stocks in the northern Bering Sea during the summers of 2017 and 2018

In the northern Bering Sea, ice coverage and retreat timing were low and early, respectively, in the 2017–2018 winter. To evaluate the effect of these anomalous ice conditions, we quantified various environmental parameters (temperature, salinity, mixed-layer depth, nutrients) and the standing stocks of various planktonic taxa (phytoplankton counts, meso- and macrozooplankton mass, jellyfish abundance) during July of 2017 and 2018. For each year, the interaction between each parameter was evaluated by structural equation modelling (SEM) analysis. Large yearly differences were detected for the interactions between environmental parameters and planktonic stocks. Thus, for 2017, a total of fifteen interactions were present between environmental parameters and various planktonic stocks. In 2018, however, only eight interactions were present. Among the interactions, four were common to the two years. It is notable that the path coefficients of these four interactions were all lower in 2018 than in 2017. These findings suggest that the small magnitude and short pulse of the phytoplankton bloom in 2018 may have failed to transfer production and energy to a higher trophic level even within the planktonic food web. Indeed, in 2018, mass mortality was reported for seabirds (two murre species) feeding on planktivorous fishes.

Hybridization does not currently pose conservation concerns to murres in the Atlantic

Hybridization can negatively impact one or both taxa involved and therefore pose conservation concerns. Climate change is expected to increase the rate of hybridization particularly in polar regions, and so investigating hybridization in Arctic and Antarctic species is important for conservation. Hybridization and genetic introgression have been observed between Pacific populations of thick-billed (Uria lomvia) and common murres (Uria aalge), species of seabirds with arctic and low arctic/temperate distributions, respectively. We employed double-digest restriction site-associated DNA sequencing (ddRADseq) to generate thousands of genome-wide markers to investigate hybridization and introgression in 133 thick-billed and 119 common murres sampled from 15 colonies throughout the North Atlantic. We used molecular assignments and principal components analysis to identify hybrids and quantify genetic introgression. Despite previous reports of hybridization between murre species in the Atlantic, we found no evidence for hybrid individuals in our dataset, and limited evidence for introgression. Our results suggest that hybridization between Atlantic murre species is rare, and does not currently pose a conservation concern for either species. Our study provides baseline data for monitoring hybridization between murres in the Atlantic to assess future impacts of climate change on these species.

Resource partitioning between sympatric seabird species increases during chick‐rearing

AbstractPartitioning of resources by competing species of seabirds may increase during periods of food shortages and elevated energy demands. Here, we examined whether food resource partitioning (differential use of foraging habitat or the consumption of different prey species) between common murres (COMU, Uria aalge) and thick‐billed murres (TBMU, U. lomvia) breeding on the same colony in the Bering Sea increases with a predictable increase in energy demands between the incubation and chick‐rearing stages of reproduction. We assessed the seasonal dynamics of food availability via corticosterone (CORT) levels and examined adult diet (via stable isotope analysis of nitrogen and carbon, SI) and chick diets (based on nest observations). We compared chick provisioning patterns and examined the characteristics of parental foraging habitat via deployment of bird‐borne temperature‐depth recorders. We found that CORT levels remained low and similar between the species and reproductive stages, reflecting relatively stable and favorable foraging conditions for both murre species during the study period. Comparisons of SI between murres and their potential prey indicated that diets were similar between the species during incubation and diverged during chick‐rearing. Chick‐rearing common and thick‐billed murres also used different foraging habitats, as reflected in travel distances to foraging areas and sea surface temperature distributions of their foraging dives. TBMUs performed shorter foraging trips, deeper dives and delivered squid to their chicks, while COMUs foraged farther from the colony, performed shallower dives, and delivered fish species to their chicks. These results suggest that food resource partitioning between murre species increased during chick‐rearing under favorable foraging conditions. Whether the dietary segregation reflected species‐specific differences in adults' foraging efficiency, differences in chicks' dietary requirements, or was a way of reducing competition remains unknown. Regardless of the causal mechanism(s), food resource partitioning might ameliorate interspecific competition between sympatrically breeding birds during periods of increased energy demands.

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.

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.

Assessment of 17 new whiskered auklet (Aethia pygmaea) microsatellite loci in 42 seabirds identifies 5–15 polymorphic markers for each of nine Alcinae species

AbstractWe isolated 17 microsatellite loci in the whiskered auklet (Aethia pygmaea) and tested them for amplification in 48 species from 13 seabird families (including 42 seabirds). Fifteen of these loci were also tested for polymorphism in 38 of the species, which included nine species of Alcinae (four auklets, Atlantic puffin, dovekie, razorbill and two murre species). On the average, nine loci were polymorphic per Alcinae species.

Responses to changes in prey availability by Common Murres and Thick-billed Murres at the Gannet Islands, Labrador

We quantified Common Murre (Uria aalge) and Thick-billed (Uria lomvia) Murre chick diets, chick-feeding rates, breeding success, chick growth, adult masses, and pair members' time spent together at site at the Gannet Islands, Labrador, in 1996 and 1997, after a decline in capelin (Mallotus villosus) abundance along the coast of southern and central Labrador. These results, with the exception of time spent at the site, were compared with those collected by other researchers at the Gannet Islands in 1981-1983, before the capelin decline. The two species responded similarly to the decline. After the decline, murres fed their chicks up to 75% fewer capelin and up to 65% more daubed shannies (Lumpenus maculatus). Feeding rates of both murre species varied among years, without respect to changes in the proportion of capelin. We found no evidence for declines in colony attendance, breeding success, chick growth, and adult mass. No data on time spent at the site were available before the decline in capelin abundance, but after the decline, off-duty murres of both species spent a mean of 10 min at their sites per feeding visit. This amount of time was short with respect to that recorded for Common Murres elsewhere, suggesting that murres' foraging effort at the Gannet Islands was high and buffered the effects of prey availability on other parameters measured. Taken together, our results suggest that murres responded to changing capelin abundance by changing their chicks' diet, but were otherwise little affected.

Food Resource Use and Diet Overlap of Common and Thick-Billed Murres at the Gannet Islands, Labrador

-We studied food resource use by two similar seabird species, Common (Uria aalge) and Thick-billed murres (U. lomvia), breeding sympatrically at the Gannet Islands, Labrador, to examine the overlap in their chicks' diet and thus to indirectly evaluate whether the two species were in competition for food. We used Monte Carlo randomization to establish whether murre chick diet overlap in 1996 and 1997 were greater than would be expected by chance. Diet overlap was higher than 75% in both years and was not lower than that predicted by the null model. To determine whether the two murre species' chick food resource use converged in ways other than diet composition, we compared timing of breeding, sizes of fish delivered to chicks, maximum dive depths and diurnal feeding patterns. In both years, the murres' chick-rearing periods overlapped almost exactly. The size of the principal item in their chicks' diets did not differ significantly. During one of two all-day feeding watches in 1997, the murres' chick-feeding peaks were concurrent, but during the other they were not. In 1997, foraging Common and Thickbilled murres dove to similar maximum depths. Taken together, these results suggest that chick food resource partitioning might have been negligible between Common and Thick-billed murres breeding at the Gannet Islands in 1996 and 1997. Received 5 November 1998, accepted 21 January 1998.

Foraging by murres (Uria spp.) at tidal fronts surrounding the Pribilof Islands, Alaska, USA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 139:1-10 (1996) - doi:10.3354/meps139001 Foraging by murres (Uria spp.) at tidal fronts surrounding the Pribilof Islands, Alaska, USA Decker MB, Hunt GL Jr We investigated the foraging distribution of 2 species of murres (Uria lomvia and U. aalge) in relation to Acoustically Determined Biomass (ADB) and hydrographic structure surrounding the Pribilof Islands, Bering Sea, Alaska, USA. The distribution and abundance of both murre species were similar; therefore, we combined data for thick-billed and common murres in the analysis. We found that murre densities were higher in frontal regions than in non-frontal regions. Maximum ADB was also found to be elevated in the frontal zone. Within frontal regions, high densities of murres were associated with regions containing relatively high levels of ADB. In contrast, we did not find significant correlations between murre density and ADB in the study area as a whole. We postulate that murres restrict their foraging to the frontal region because prey can be located more predictably within this zone than in other areas in the vicinity of the Pribilof Islands. Seabird distribution · Tidal fronts · Urialomvia · Uria aalge · Murres · Bering Sea Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 139. Publication date: August 29, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Murre foraging, epibenthic sound scattering and tidal advection over a shoal near St. George Island, Bering Sea

MARINE ECOLOGY PROGRESS SERIES Mar. Ecol. Prog. Ser. Published July 2 Murre foraging, epibenthic sound scattering and tidal advection over a shoal near St. George Island, Bering Sea Kenneth 0. Coylel, George L. Hunt, ~ r Mary ~ , Beth ~ e c k e r Thomas J. weingartner1 'Institute o l Marine Science, School of Fisheries and Ocean Sciences. University of Alaska Fairbanks, Fairbanks. Alaska 99775-1080, USA 'Department of Ecology and Evolutionary Biology, University of California, Irvine. Irvine, California 92717, USA ABSTRACT: High concentrations of 2 murre species (Uria aalge and U. lomvia) were observed forag- ing over a submarine ridge on the east side of St. George Island. Bering Sea, usually in the morning. Simultaneous measurements of tidally generated current velocity and acoustically determined biomass along transects over the ridge demonstrated that the murres were concentrating over a dense epi- benthic sound-scattering layer near the ridge crest on southward ebb tide currents. Samples taken by net tows through the layer contained high numbers of euphausiids (Thysanoessa inerrnis and T. raschii). Stomachs of murres collected in the area contained predominantly euphausi~ds. When tidal currents reversed from southward to northward, the sound-scattering layer was carried northward off the ridge and the murres left the area. We hypothesize that the euphausiid aggregations resulted from the interaction of the die1 downward migration of euphausiids in the morning, bottom topography and tidal currents. INTRODUCTION Energy flow through marine ecosystems depends on a number of variables, one of which is prey concentra- tion. While high primary production may result in favorable conditions for grazers, the efficiency of energy transfer from grazer stocks to higher trophic levels is sensitive to physical processes which influ- ence the concentration of prey. The complex inter- action of animal behavior patterns and physical processes can produce a patchy distribution of zoo- plankton and micronekton (Omori & Hamner 1982, Sameoto 1983), thereby affecting feeding conditions of high level consumers. Physical processes can transport weakly swimming or drifting organisms horizontally (Banse 1986, Schel- tema 1986, Stancyk & Feller 1986). Tidal currents and wind-induced turbulence can vertically disperse hori- zontal layers (Haury et al. 1990, Incze et al. 1990), or interact with bathymetry to upwell organisms to the surface (Vermeer et al. 1987, Brown & Gaskin 1988). In addition, physical processes and behavior may interact O Inter-Research 1992 to affect the horizontal or vertical distribution of some species (Norcross & Shaw 1984, Epifanio 1987, Genin et al. 1988). Schneider et al. (1987) hypothesized that the interaction of flow gradients with bathymetry would result in concentrations of prey that were pre- dictable in time and space. Whatever the origin of zooplankton aggregations, they are an important source of energy to predators. For example, baleen whales seek out and prey on zoo- plankton aggregations (Kenney et al. 1986, Wishner et al. 1988) and the diets of fish are known to be influ- enced by prey distribution (Owen 1981, Genin et al. 1988). A variety of marine birds prey upon zooplankton aggregations associated with frontal zones (Bradstreet & Brown 1985, Schneider et al. 1987, 1990, Hunt 1990, Hunt & Harrison 1990), and tidal upwellings (Vermeer et al. 1987, Brown & Gaskin 1988). Spatially and temporally predictable prey aggregations may be of particular importance to foraging birds (Schneider et al. 1987). In this paper we examine the effects of tidal currents, bathymetry and the diurnal vertical migra- tion of euphausiids on the feeding behavior of thick-

Community structure of arthropod ectoparasites on Alaskan seabirds

A total of 28 species of arthropods was recovered from 29 common murres (Uria aalge), 8 thick-billed murres (Uria lomvia), 22 black-legged kittiwakes (Rissa tridactyla), and 10 red-legged kittiwakes (Rissa brevirostris) collected from the Pribilof Islands, Alaska, U.S.A. The ectoparasite community on each bird species almost invariably consisted of three species of chewing lice, two species of ticks, and five to nine species of mites. Astigmatid feather mites (Alloptes spp., Laronyssus martini (Trouessart)) were the most numerous group of ectoparasites except on black-legged kittiwakes on which Ixodes ticks were the most abundant. The second most abundant taxa were ticks on common murres and thick-billed murres, and quill mites (Syringophilidae) on red-legged kittiwakes. Kittiwakes usually supported more diverse communities of ectoparasites than did murres, probably because of differences in nesting and foraging behavior. Ectoparasite communities between the congeneric species of birds were particularly similar in terms of species composition and general structure, and supported our hypothesis that phylogenetic relatedness of hosts is reflected in similarity of their ectoparasite communities. Community structure of ectoparasites was much more similar between the two murre species than between the two kittiwake species, probably because of gregarious flocking and mixed-species nesting of murres.

Ecological relationships between Common Murres, Uria aalge, and Thick-billed Murres, Uria lomvia, at the Gannet Islands, Labrador. III. Feeding ecology of the young

A simultaneous comparison of the foods of Common Murre, Uria aalge, and Thick-billed Murre, Uria lomvia, chicks at the same location showed that the species composition of fish fed to chicks of the two murre species differed significantly. In both years of the study, Common Murre chicks were fed predominantly capelin, Mallotus villosus (78–80% by weight), whereas Thick-billed Murre chicks were fed mainly daubed shanny, Lumpenus maculatus (61–70% by weight). Thick-billed Murres tended to feed their chicks more frequently than Common Murres, probably because in both years the mean caloric value of their prey was lower than that of the Common Murre's. No other statistically significant interspecific differences were consistent between years. Prey lengths and weights overlapped considerably between the murre species, and the caloric intake of chicks showed no consistent interspecific difference. Marked interyear differences in feeding rate, prey size, and caloric intake occurred in both species. In 1982 ice breakup was late, and the murres' breeding seasons were delayed; this appeared to result in poor synchronization between the temporal pattern of food availability and the timing of each species' chick-rearing period, and the caloric intakes of chicks of both species were lower in that year than in 1983.

Ecological relationships between Common Murres, Uria aalge, and Thick-billed Murres, Uria lomvia, at the Gannet Islands, Labrador. II. Breeding success and site characteristics

At the Gannet Islands, Labrador, the proportion of Thick-billed Murres (Uria lomvia) that successfully reared a chick that left the colony was significantly lower (mean = 63%) than that of Common Murres (Uria aalge; 82%) in each of 3 years of study. The physical and social features of the breeding site were the only factors known to influence breeding success. For both murre species, breeding success increased with ledge width, and whereas most Common Murres bred on the widest ledges, relatively few Thick-billed Murres did so. The success of each species did not differ significantly on ledges of the same width. We suggest that Common and Thick-billed murres competed for breeding sites and that Common Murres obtained a disproportionate share of the "best" sites. This occurred because Common Murres outnumbered Thick-billed Murres by about 40:1 and because cliff habitat was in short supply. Whereas Thick-billed Murres bred only on cliffs, Common Murres were able to breed on cliffs and flat ground nearer sea level. Additional circumstantial evidence supports the idea that Common and Thick-billed murres at the Gannet Islands compete for breeding sites.