Seabird Diet Research Articles

Dietary change in seabirds on Guangjin Island, South China Sea, over the past 1200 years inferred from stable isotope analysis

Quantifying variation in animals’ paleodiet from the fossil record is difficult as a continuous record of their remains is difficult to obtain. Here we assess dietary change in seabirds from Guangjin Island, Xisha Archipelago, South China Sea, by using stable nitrogen isotopes in seabird bones and prey remains collected from a coral sand ornithogenic sediment profile. δ15N of seabird bone collagen varied from 11.7‰ to 14.1‰ (averaging 12.8‰ ± 0.4‰), but that of fish bones and scales showed minor variations. Flying fish and squid are two favorite foods of tropical seabirds, and the average values of muscle δ15N in typical flying fish and squid samples were 9.2‰ and 10.2‰, respectively. Based on nitrogen isotope mass balance calculation, we conclude that flying fish accounts for 80% ± 40% of seabird diet averaged over the past 1200 years, but this prey accounted for only about 37% ± 30% during the ‘Little Ice Age’ (AD 1400–1850). Flying fish averaged up to 88% ± 2% during the ‘Medieval Warm Period’ (AD 850–1200), close to modern observed value of 89.6%. Thus, it appears that seabirds on Guangjin Island mainly preyed on flying fish during warm periods, and shift to squid during cooler periods. Our results suggest that recent global warming and human activities have likely caused a rapid decrease in tropical seabird population and dietary shift.

Anomalous ecosystem dynamics following the apparent collapse of a keystone forage species

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 553:185-202 (2016) - DOI: https://doi.org/10.3354/meps11761 Anomalous ecosystem dynamics following the apparent collapse of a keystone forage species Kenneth T. Frank1,2,*, Brian Petrie1, Daniel Boyce2, William C. Leggett2 1Fisheries and Oceans Canada, Bedford Institute of Oceanography, Ocean Sciences Division, Dartmouth, Nova Scotia B2Y 4A2, Canada 2Department of Biology, Queen’s University, Kingston, Ontario K7L 3N6, Canada *Corresponding author: kenneth.frank@dfo-mpo.gc.ca ABSTRACT: Major groundfish populations in the western Atlantic north of Georges Bank/Western Scotian Shelf experienced near-total population collapses beginning in the late 1980s-early 1990s. Explosive increases in the abundance of their pelagic fish and invertebrate prey (notably capelin, sand lance, herring, shrimp and snow crab) generally followed. However, several investigators have concluded, based on the results of annual acoustic surveys, that the lightly exploited capelin stock in the Newfoundland/Labrador (NL) region experienced a sudden 6.8 Mt (98%) decline in biomass from 1990 to 1991 coincident with the groundfish collapse. Given the enormity, duration and unexpected nature of this decline, it was characterized as a collapse. The contrasting response of this capelin stock to the groundfish collapse relative to other North Atlantic (NA) ecosystems prompted us to undertake systematic analyses of the NL ecosystem. The reported capelin collapse in NL should have induced significant responses of trophically linked species, as have been reported in other NA ecosystems. We found little evidence of changes in the population abundance, diet and condition of marine mammals, cod, seabirds and zooplankton, in indexes of the areal occupancy and spawning biomass of capelin, or of environmental effects. These results strongly support the hypothesis that the reported collapse did not occur. Profound seasonal distribution changes, a fixed in time and space acoustic survey in a restricted portion of the distributional range of capelin, and the possibility that NL capelin stock has become less migratory provide a more robust and consistent explanation of the observations. KEY WORDS: Forage fish · Stock collapse · Ecosystem response · North Atlantic · Acoustic surveys · Migration Full text in pdf format Supplementary material PreviousNextCite this article as: Frank KT, Petrie B, Boyce D, Leggett WC (2016) Anomalous ecosystem dynamics following the apparent collapse of a keystone forage species. Mar Ecol Prog Ser 553:185-202. https://doi.org/10.3354/meps11761 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 553. Online publication date: July 14, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Ontogenetic and spatial variability in trophic biomarkers of juvenile saffron cod (Eleginus gracilis) from the Beaufort, Chukchi and Bering Seas

Climate models indicate the Arctic will undergo dramatic environmental change with forecasted increases in temperature and river runoff. Saffron cod (Eleginus gracilis) is abundant in nearshore waters and appears in the diet of many Arctic sea birds and marine mammals; however, little is known about its early ecology and consequently how they might be affected by environmental changes. We aimed to characterize the mechanisms of spatial and ontogenetic variation in trophic biomarkers (lipid classes, fatty acids and bulk C and N stable isotopes) of saffron cod from the Western Arctic, Chukchi and Bering Seas. Size-standardized analyses showed a significant difference in lipid condition metrics and trophic biomarkers as a function of survey location. Both ontogeny and sampling location played an important role in determining lipid stores with elevated levels in both small offshore juveniles ( 75 mm). Higher lipid storage in Arctic juveniles was associated with elevated levels of diatom fatty acid markers, but not with nearshore carbon input. Increased lipids were found in age-1 juveniles from Prudhoe Bay in the Western Beaufort that were feeding at a lower trophic level than similarly sized age-0 juveniles from surface trawls in the Bering Sea. The use of otolith annuli revealed two discrete patterns of growth that help explain the trade-offs between energy storage and rapid growth that diverge between the Arctic and Bering Sea. Laboratory temperature-growth experiments confirmed that saffron cod have a eurythermal growth response and are able to store excess lipids at temperatures as high as 20 °C.

Dietary change in Cape gannets reflects distributional and demographic shifts in two South African commercial fish stocks

Abstract Seabirds are upper trophic level predators, and are often highly sensitive to changes in the availability of their prey. Altered prey assemblages resulting from fluctuations in oceanographic conditions may be mirrored by shifts in seabird diet. Long-term studies of dietary change in seabirds therefore provide valuable insight into the nature of environmental shifts within the systems in which they forage. In recent decades, the Agulhas region in South Africa has undergone significant oceanographic change related to warming and intensification of the Agulhas current. Concurrent with this change, the population of Cape gannets Morus capensis at Bird Island, Algoa Bay, has grown rapidly, probably as a result of an increased availability of its dominant prey items, sardine Sardinops sagax and anchovy Engraulis encrasicolus. Using one of the longest and most complete time-series available on diet of a seabird (spanning 34 years), we tested for changes in composition and the abundance of dominant prey species of this population. These observed changes were also compared with acoustic survey estimates of their biomass, and annual catch data. Since 1979, the prey composition has remained similar, but the dietary contribution of sardine and anchovy, which fluctuated inversely to each other, increased over the study period. These shifts seem to be reflective of fluctuations in the stock size of sardine and anchovy. Conversely, a third species, saury Scomberesox saurus, dominant in the non-breeding diet of the 1980s, decreased significantly in dietary abundance over the following two decades. It is likely that dietary shifts of Cape gannets at Bird Island were related to climate-mediated oceanographic change. The implications of such changes are discussed.

Temporal dynamics of top predators interactions in the Barents Sea.

The Barents Sea system is often depicted as a simple food web in terms of number of dominant feeding links. The most conspicuous feeding link is between the Northeast Arctic cod Gadus morhua, the world's largest cod stock which is presently at a historical high level, and capelin Mallotus villosus. The system also holds diverse seabird and marine mammal communities. Previous diet studies may suggest that these top predators (cod, bird and sea mammals) compete for food particularly with respect to pelagic fish such as capelin and juvenile herring (Clupea harengus), and krill. In this paper we explored the diet of some Barents Sea top predators (cod, Black-legged kittiwake Rissa tridactyla, Common guillemot Uria aalge, and Minke whale Balaenoptera acutorostrata). We developed a GAM modelling approach to analyse the temporal variation diet composition within and between predators, to explore intra- and inter-specific interactions. The GAM models demonstrated that the seabird diet is temperature dependent while the diet of Minke whale and cod is prey dependent; Minke whale and cod diets depend on the abundance of herring and capelin, respectively. There was significant diet overlap between cod and Minke whale, and between kittiwake and guillemot. In general, the diet overlap between predators increased with changes in herring and krill abundances. The diet overlap models developed in this study may help to identify inter-specific interactions and their dynamics that potentially affect the stocks targeted by fisheries.

Seabird diet changes in northern Hudson Bay, 1981-2013, reflect the availability of schooling prey

Ongoing climate change is altering Arctic marine ecosystems with major conse- quences for food-webs. Seabirds, by foraging over large marine areas but returning regularly to their breeding colonies, provide a good medium for tracking such changes. We studied the prey delivered to nestling thick-billed murres Uria lomvia at a colony in northern Hudson Bay, Canada, over the period 1981−2013. During that period, ice conditions in the region altered substantially, with earlier break-up and clearance. This change was not gradual but mainly occurred in the mid- 1990s. Breeding chronology also advanced, but not as fast as early summer ice clearance advanced. Ice conditions strongly affected diet, presumably reflecting the change in the timing of breeding relative to ice clearance. Of the dominant species in the diet, the proportion of Arctic cod Boreogadus saida decreased and the proportion of capelin Mallotus villosus increased over the 33 yr period, even after ice effects were taken into account, suggesting a progressive and cumu- lative effect of environmental change on the marine community. Those cumulative changes were manifested primarily in the diet representation of the most frequent taxa (cod and capelin), with variation in secondary diet components being driven by the availability of the dominant taxa. Diet diversity, representing an increase in the proportion of benthic fish (stichaeids, zoarcids, pholids and sculpins) and invertebrates (squid, amphipods and crustaceans), increased when ice cover was low, and hatching was late relative to ice break-up. Chick growth rates were low when the proportion of benthic fish was high. Hence, although it appears that growth rates are influenced by diet composition, it is more likely that they reflect the availability of the dominant schooling prey species, rather than any nutritional deficiency in benthic species.

Seabirds and marine mammals redistribute bioavailable iron in the Southern Ocean

Biological vectors are important for redistribution of nutrients in many ecological systems. While availability of iron (Fe) to phytoplankton limits pelagic productivity in the Southern Ocean, biomagnification within marine food webs can lead to high concentrations of Fe in the diet of seabirds and marine mammals. We investigated patterns in concentrations of the micronutrients Fe, Co, Zn and Mn, and the toxins Cd and As, in the guano of oceanic, coastal and predatory seabirds and in faeces of 2 species of marine mammals that congregate to breed in the sub-Antarctic Auckland Islands. We found that much of the variability in concentrations of Fe, Co, Zn and Mn among species could be explained by foraging behaviour and by trophic position. We observed concentrations of Fe to be 8 orders of magnitude higher in the guano of predators and coastal foragers than in the sub-Antarctic mixed layer. High concentrations of As and Cd were associated with organic matter sources from macroalgae. Analyses of the molar ratio Fe:Al indicated that Fe within food webs supporting seabirds has likely been extensively recycled from its lithogenic source. Patterns in Fe:N among species indicated that Fe is concentrated 2 to 4 orders of magnitude in the guano of seabirds compared to limiting conditions for phytoplankton growth in sub-Antarctic waters. These data highlight the potential role of seabirds and marine mammals in the redistribution of micronutrients in the Southern Ocean and their likely role as key nutrient vectors in the ecosystem, particularly around the sub-Antarctic islands during the breeding season.

An holistic ecological analysis of the diet of Cory's shearwaters using prey morphological characters and DNA barcoding.

Knowledge of the dietary choices and trophic niches of organisms is the key to understanding their roles in ecosystems. In seabird diet studies, prey identification is a difficult challenge, often yielding results with technique-specific biases. Additionally, sampling efforts are often not extensive enough to reveal intrapopulational variation. Immature animals, which may constitute up to 50% of a population, may occupy a significantly different trophic niche to more experienced birds, but this remains largely unexplored. We investigated the diet of Cory's shearwater (Calonectris diomedea) from Selvagem Grande, an island located off the northwest African coast, collecting a total of 698 regurgitate samples over three consecutive breeding seasons. The diet was assessed using two complementary approaches for prey identification: conventional morphological analysis (using fish vertebrae, otoliths and cephalopod beaks) and DNA barcoding of the 16S rRNA mitochondrial gene, in cases where a positive identification could not be retrieved. Species assignments employed BLAST and distance-based methods, as well as direct optimization of the tree length based on unaligned sequences in POY. This method resulted in robust tree estimates and species assignments, showing its potential for DNA barcoding of stomach contents using hypervariable markers such as the 16S. The molecular approach increased taxonomic resolution and revealed an additional 17 taxa. Diet differed significantly according to breeding status, sex, breeding phase (prelaying and chick rearing) and year. Such direct evidence of trophic segregation within the same population has rarely been shown in seabirds and highlights the importance of including such variables in ecosystem-based management approaches.

Linking dietary shifts and reproductive failure in seabirds: a stable isotope approach

Summary Diet‐related breeding failure in seabirds has been attributed to declines in key prey abundance, the quality of prey and overall prey availability. However, identifying which aspect of diet is responsible for reproductive failure is challenging due to the practicalities of measuring prey utilization and the actual availability and abundance of those resources. In this study, stable isotope‐based Bayesian models, in combination with indices of resource availability, were used to assess the links between prey availability, seabird diet and reproductive success in a generalist, inshore top predator, the little penguin, Eudyptula minor. The most probable causes for the sharp decrease in little penguin reproductive performance were diminished localized populations of anchovies, Engraulis australis, in combination with the scarcity of alternative prey. Low dietary diversity and the consumption of low trophic value prey were observed in this period. In the contrasting following year, penguins consumed increased levels of anchovy as well as a high diversity of prey. High dietary diversity and the consumption of high trophic value prey were observed in birds' pre‐breeding and breeding diet and likely led to early breeding and high reproductive success. Our results highlight that resource abundance and the availability of a variety of prey taxa are critical factors in enabling this inshore seabird to adjust to changes in environmental conditions and fluctuations in prey. An understanding of seabird diet is integral to their conservation and management. Monitoring seabird trophic niche dimensions and reproductive parameters can elucidate causes for population declines and can provide information about particular prey species and foraging locations that require protection.

Use the backbone of your samples: fish vertebrae reduces biases associated with otoliths in seabird diet studies

A literature review showed that most recent conventional dietary studies of Procellariiformes have used otoliths alone to identify fish prey. Using data from a dietary study of Cory’s Shearwaters Calonectris diomedea, based on 673 regurgitates from adult birds, we quantitatively compared the contribution of otoliths and vertebrae for prey identification and quantification. By using otoliths alone, the importance of the main fish prey was greatly underestimated and several species would have been considered completely absent. Therefore, we strongly recommend the combined use of vertebrae, otoliths and other fish remains in order to improve the quality of dietary studies of seabirds.

Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web

AbstractPinchuk, A. I., Coyle, K. O., Farley, E. V., and Renner, H. M. 2013. Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web. – ICES Journal of Marine Science, 70: 1244–1254. The eastern Bering Sea shelf experienced a sequence of warm years after a regime shift in the late 1970s. Following a series of unusually warm years in the early 2000s, the climate shifted again in 2007 to a series of extremely cold years that were marked by intense ice coverage and late ice retreat. Spatial and temporal variability in zooplankton communities during the recent cold period was investigated as part of the collaborative BEST-BSIERP program. An increasing presence of the Arctic hyperiid Themisto libellula, which had not been reported from the southeastern Bering Sea since the 1970s, was observed in the Middle Shelf Domain, indicating a developing structural shift in the zooplankton community in response to continuous cold conditions. Simultaneously, T. libellula became an increasingly dominant prey in the diets of zooplanktivorous fish and seabirds, demonstrating the important role for T. libellula in the pelagic food web. Our analysis suggests that T. libellula is capable of controlling copepod populations, thus it may become a potential contributor to top-down regulation of Calanus spp. in the eastern Bering Sea.

Seabird diets provide early warning of sardine fishery declines in the Gulf of California

Small pelagic fisheries show wide fluctuations, generally attributed to oceanographic anomalies. Most data on these fisheries come from landings, often reporting sustained catches-per-unit-effort (CPUEs) until a decline occurs. Fishery-independent data are important as management tools. In this study we show that the proportions of Pacific Sardine and Northern Anchovy in the diet of three seabird species (California Brown Pelicans, Heermann's Gulls, and Elegant Terns) nesting in spring in the Gulf of California show significant relationships with CPUEs during the following season in gulls and terns, or during the same season in pelicans. As sardine availability for seabirds declines, CPUEs remain high until the fishery falls, one or two seasons later. A declining proportion of sardines in the seabirds' diet, combined with the status of the Pacific warm-phase anomaly (El Niño), give a reliable forecast of diminishing CPUEs and signals the need to reduce fishing efforts in the ensuing season.

Diatom-Specific Highly Branched Isoprenoids as Biomarkers in Antarctic Consumers

The structure, functioning and dynamics of polar marine ecosystems are strongly influenced by the extent of sea ice. Ice algae and pelagic phytoplankton represent the primary sources of nutrition for higher trophic-level organisms in seasonally ice-covered areas, but their relative contributions to polar marine consumers remain largely unexplored. Here, we investigated the potential of diatom-specific lipid markers and highly branched isoprenoids (HBIs) for estimating the importance of these two carbon pools in an Antarctic pelagic ecosystem. Using GC-MS analysis, we studied HBI biomarkers in key marine species over three years in Adélie Land, Antarctica: euphausiids (ice krill Euphausia crystallorophias and Antarctic krill E. superba), fish (bald notothens Pagothenia borchgrevinki and Antarctic silverfish Pleuragramma antarcticum) and seabirds (Adélie penguins Pygoscelis adeliae, snow petrels Pagodroma nivea and cape petrels Daption capense). This study provides the first evidence of the incorporation of HBI lipids in Antarctic pelagic consumers. Specifically, a di-unsaturated HBI (diene) of sea ice origin was more abundant in ice-associated species than in pelagic species, whereas a tri-unsaturated HBI (triene) of phytoplanktonic origin was more abundant in pelagic species than in ice-associated species. Moreover, the relative abundances of diene and triene in seabird tissues and eggs were higher during a year of good sea ice conditions than in a year of poor ice conditions. In turn, the higher contribution of ice algal derived organic matter to the diet of seabirds was related to earlier breeding and higher breeding success. HBI biomarkers are a promising tool for estimating the contribution of organic matter derived from ice algae in pelagic consumers from Antarctica.

Analysis of fatty acids and fatty alcohols reveals seasonal and sex-specific changes in the diets of seabirds

A key challenge in ecology is to find ways to obtain complete and accurate information about the diets of animals. To respond to this challenge in seabirds, traditional methods (usually stomach content analysis or observations of prey at nests) have been supplemented with indirect methods or molecular trophic markers. These techniques have the potential to extend the period of investigation outside the few short months of breeding and avoid biases. Here, we use an analysis of fatty acids (FAs) and fatty alcohols (FALs) from blood, adipose tissue and stomach oil to investigate how the diets of male and female common guillemots (Uria aalge), black-legged kittiwakes (Rissa tridactyla) and northern fulmars (Fulmarus glacialis) differed through the sampling period (prelaying and breeding season) and by sex. Diets of both sexes of all three species generally varied across the season, but sex differences were apparent only in fulmars during prelaying. Our study shows that FA/FAL analysis can provide significant insights into diets of seabirds, in particular periods of the annual cycle which are not readily studied using traditional methods.

How do cephalopods become available to seabirds: can fish gut contents from tuna fishing vessels be a major food source of deep-dwelling cephalopods?

AbstractXavier, J. C., Cherel, Y., Roberts, J., and Piatkowski, U. 2013. How do cephalopods become available to seabirds: can fish gut contents from tuna fishing vessels be a major food source of deep-dwelling cephalopods? – ICES Journal of Marine Science, 70:46–49. Cephalopods are important prey for numerous seabird species. However, the physical mechanisms by which cephalopods (particularly species considered as deep-dwelling) become available to seabirds are poorly understood, and it has recently been suggested that the discarded stomachs of gutted fish captured by tuna longliners can be a major source of deep-dwelling species. Here, we identify some deep-dwelling cephalopods that appear in the diet of seabirds, review the current knowledge of their vertical distribution, and compare the stomach contents of commercially captured tuna with those of seabirds foraging in the same area. The limited available information leads us to conclude that tuna longliners are unlikely to be a major source of deep-dwelling cephalopods for seabirds. However, much more information is required on the ecology of seabird prey, particularly commercially unexploited cephalopod species, which may be obtained from scientific cruises devoted to cephalopod biological research. In addition multispecies/foodweb modelling studies may be required to explore potential interactions between seabirds, their predators and prey, and commercial fishing operations.

Effect of El Niño on the diet of a specialist seabird, Sula nebouxii, in the warm eastern tropical Pacific

Reductions in the availability of energetically valuable prey associated with the El Nino Southern Oscillation (ENSO) may force seabirds to switch to low-energy prey or smaller prey, with consequent effects on their fitness. Impacts of ENSO on seabird diet have been docu- mented in several regions but remain unexplored in the warm eastern tropical Pacific. Analysis of 5 yr of data on the blue-footed booby Sula nebouxii, a seabird specialized on small pelagic fish, revealed that both sexes switch diet and capture fewer types of prey when warm El Nino condi- tions prevail during the breeding season. Moreover, ENSO-related alternations in the relative abundances of anchovies and herrings, the main prey of these boobies and important commercial fishes in the region, were associated with boobies feeding on more and larger anchovies and fewer and smaller herrings during warm El Nino events, and vice versa during cold La Nina episodes. Females consumed herrings more frequently than males across the 5 yr and consistently fed on larger anchovies and herrings than males, with these differences likely due to this booby's reversed sexual size-dimorphism. We conclude that diet composition and prey size of boobies may be sensitive to variation in relative availabilities of different prey species associated with the ENSO, making these birds robust indicators of environmental fluctuations in the warm eastern tropical Pacific. Inter-annual variations in the availability of herrings, probably the most energet- ically valuable prey for these boobies, may explain the large ENSO-related variations in booby reproduction documented previously.

Extending an indicator: year-round information on seabird trophic ecology from multiple-tissue stable-isotope analyses

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 461:233-243 (2012) - DOI: https://doi.org/10.3354/meps09835 Extending an indicator: year-round information on seabird trophic ecology from multiple-tissue stable-isotope analyses Keith A. Hobson1,*, Alexander L. Bond1,2 1Environment Canada, 11 Innovation Blvd., Saskatoon, Saskatchewan S7N 3H5, Canada 2Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Saskatchewan S7N 5E2, Canada *Email: keith.hobson@ec.gc.ca ABSTRACT: Stable isotope analysis of tissues of seabirds and their prey has proven to be an extremely useful tool in seabird dietary studies in general and in the potential use of seabirds as ecological indicators in particular. The measurement of stable carbon (δ13C) and nitrogen (δ15N) isotope values is important since they provide information on source of feeding and trophic position, respectively. However, the stable isotope approach provides information on spatial and trophic ecology of seabirds during a window of temporal integration that depends on the elemental turnover rate in the tissue being measured. Most researchers have relied on only 1 or 2 tissue types to study seabird diets and foraging ecology. Here, the potential for modeling trophic position and habitat use by seabirds over the annual cycle is demonstrated by using multiple tissues from the same individual. Isotopic measurements of bone collagen provide information integrated over the lifetime of the individual and those of feathers during the post-breeding molt period. Analysis of liver provides information integrated over the previous week and that of muscle integrated over a few months. We developed multi-tissue trophic models for thick-billed murre Uria lomvia, dovekie Alle alle, black guillemot Cepphus grylle, glaucous gull Larus hyperboreus, northern fulmar Fulmarus glacialis, black-legged kittiwake Rissa tridactyla, and ivory gull Pagophila eburnea using the Northwater Polynya in Northern Baffin Bay, 1998 to 1999. The careful application of stable isotope methods to a spectrum of tissue types represents a powerful means of extending our ability to investigate diet and potentially to use seabirds as ecological indicators. KEY WORDS: Stable isotopes · Carbon-13 · Nitrogen-15 · Seabirds · Temporal integration Full text in pdf format PreviousNextCite this article as: Hobson KA, Bond AL (2012) Extending an indicator: year-round information on seabird trophic ecology from multiple-tissue stable-isotope analyses. Mar Ecol Prog Ser 461:233-243. https://doi.org/10.3354/meps09835 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 461. Online publication date: August 08, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Seabird diet indicates changing Arctic marine communities in eastern Canada

Seabird diet indicates changing Arctic marine communities in eastern Canada J. F. Provencher*, A. J. Gaston, P. D. O’Hara, H. G. Gilchrist Department of Biology, University of Victoria, Victoria, British Columbia V8W 3N5, Canada Science and Technology Branch, National Wildlife Research Centre, Carleton University, Ottawa, Ontario K1A 0H3, Canada Canadian Wildlife Service, Sidney, British Columbia V8L 4B2, Canada

Interannual changes in zooplankton on the West Spitsbergen Shelf in relation to hydrography and their consequences for the diet of planktivorous seabirds

AbstractKwasniewski, 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.

From lavage to lipids: estimating diets of seabirds

Understanding seabird marine habitat affinities, at-sea behavior, variability in repro- ductive success, migratory patterns, phenology, and other life history traits depends primarily on knowledge of the prey that they consume. Traditionally, estimating diets has been done through classification and enumeration of prey remains found in stomach contents of seabirds collected at sea, as well as chick meals, pellets, and feces collected at breeding colonies. These techniques have the advantage of high taxonomic resolution of prey, but suffer from biases due to the under - estimation of soft-bodied or small prey that are digested completely and overestimation of prey with durable parts that are retained for long periods of time. Recent innovations in 2 biochemical assays of seabird tissues—stable isotope and fatty acid analyses—have greatly expanded knowledge of seabird diets and have advanced our understanding of the ways in which seabirds can indicate in- ter-seasonal, annual, decadal, and longer shifts in oceanographic conditions over varying spatial scales. Advances in statistical approaches to these data have provided new ways in which prey can be identified and quantified. When applied in combination, these 3 techniques (traditional diet sampling, and stable isotope and fatty acid analyses) have the potential to reveal pathways of energy flux across marine ecosystems and to provide new insight into marine ecosystem dynamics. We review the basic principles of these approaches to determining seabird diet and emphasize the need for more formal conceptual and statistical integration of methods to advance this field.