Annual Variation in Great Skua Diets: The Importance of Commercial Fisheries and Predation on Seabirds Revealed by Combining Dietary Analyses

Bearhop, Stuart; Thompson, David R.; Phillips, Richard A.; Waldron, Susan; Hamer, Keith C.; Gray, Catherine M.; Votier, Stephen C.; Ross, Barbara; Furness, Robert W.

doi:10.1650/0010-5422(2001)103[0802:avigsd]2.0.co;2

Cited by 39 publications

(31 citation statements)

References 20 publications

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“…On the basis of our results, the δ 15 N signature, as previously suggested (Bearhop et al 2001, Cherel & Hobson 2007, Phillips et al 2009), is not only affected by diet but is also largely influenced by oceanic processes. Our findings imply that, since seabirds tend to concentrate and move between habitats of enhanced and changing productivity, such as shelf edges, frontal zones and upwellings (Weimerskirch 2007), the simultaneous influence of feeding ecology and baseline spatial variation as a result of oceanic processes on their δ 15 N signatures may be frequent.…”

Section: Discussionsupporting

confidence: 82%

Influence of trophic ecology and spatial variation on the isotopic fingerprints of seabirds

Moreno¹,

Jover²,

Velando³

et al. 2011

Mar. Ecol. Prog. Ser.

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Section: Discussionsupporting

confidence: 82%

Influence of trophic ecology and spatial variation on the isotopic fingerprints of seabirds

Moreno¹,

Jover²,

Velando³

et al. 2011

Mar. Ecol. Prog. Ser.

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“…These studies suggest seabirds then take a larger variety of prey, including many species that are relatively low in energy density (e.g. Bradstreet and Brown 1985;Sonntag and Hüppop 2005;Hedd and Montevecchi 2006), and often at a lower trophic level (Bearhop et al 2001). In Norwegian waters, Mehlum (2001) showed that Barents Sea Common Guillemots and Brünnich's Guillemots (Uria lomvia) that brought fish to their young had much smaller prey, e.g.…”

Section: Discussionmentioning

confidence: 99%

Optimal foraging in chick-raising Common Guillemots (Uria aalge)

2010

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The Norwegian population of the Common Guillemot Uria aalge has declined by [95% since the 1960s, and is classified as critically endangered in the Norwegian Red List. Much of the recent decline has been attributed to reduced food availability, but without extensive documentation of adult diet. Instead, chick diet has been considered a proxy of adult diet during the breeding season in many Norwegian studies. However, central-place foraging theory, especially for single-prey loaders, predicts that this may not be so, and this study directly compares the diet of adult and chick Common Guillemots during the breeding season at a colony in NE Norway. Whereas chicks were fed mainly capelin (Mallotus villosus) and sandeels (Ammodytes sp.), most of the adult diet consisted of the two youngest year classes of Gadidae, probably cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). A successful ecosystem management of seabirds is dependent on a full understanding of how prey quality, abundance and availability influence seabird populations and their viability, such that knowing the true diet of adult Common Guillemots has important implications in the modelling and management of the Norwegian populations.

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“…Great skuas at St Kilda consume very large numbers of Leach's storm-petrels, as well as some European storm-petrels Hydrobates pelagicus and Manx shearwaters Puffinus puffinus (Phillips et al 1997;1999b), three species which only attend the colony above ground at night. However the technique used by skuas to obtain these prey is unknown, with some debate as to whether prey are caught close to the breeding colonies at night or while at sea (Phillips et al 1997;Bearhop et al 2001). Previous work has shown that at colonies, non-breeding Procellariforms are at greater risk of predation at night than breeding birds, because they remain above ground for longer periods while searching for a mate and a potential breeding site (Furness 1987;Mougeot et al 1998;Mougeot and Bretagnolle 2000).…”

Section: Introductionmentioning

confidence: 99%

Nocturnal foraging by great skuas Stercorarius skua: implications for conservation of storm-petrel populations

et al. 2006

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At St Kilda, Outer Hebrides, a large colony of great skuas Stercorarius skua feed extensively on one of the largest colonies of Leach's storm-petrels Oceanodroma leucorhoa in Europe, but little is known about the dynamics of this predator-prey system. Recently published population estimates of storm-petrels make it possible to estimate the impact of skua predation for the first time. Although skuas in the southern hemisphere catch petrels attending breeding colonies at night, it is not known whether congeners in the northern hemisphere also forage during the hours of darkness. We found (using radio-transmitters) that skuas regularly forage at night and (using light intensifying equipment) observed them catching storm-petrels at night. However, skuas also foraged during daylight hours, and it is unknown whether they might also catch storm-petrels at sea. Data on diet composition reveals that the proportion of storm-petrels in skua diet declined between 1996 and 1997, but remained constant thereafter. Although a large proportion of the storm-petrel prey is likely to consist of non-breeders, numbers consumed suggest that breeders and an unknown quantity of transients may also been eaten. The numbers of storm-petrels eaten are not sustainable and may result in substantial long-term population declines. Under current conditions, maintenance of large populations of both Leach's storm-petrels and great skuas at St Kilda appears to be mutually exclusive.

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Annual Variation in Great Skua Diets: The Importance of Commercial Fisheries and Predation on Seabirds Revealed by Combining Dietary Analyses

Cited by 39 publications

References 20 publications

Influence of trophic ecology and spatial variation on the isotopic fingerprints of seabirds

Influence of trophic ecology and spatial variation on the isotopic fingerprints of seabirds

Optimal foraging in chick-raising Common Guillemots (Uria aalge)

Nocturnal foraging by great skuas Stercorarius skua: implications for conservation of storm-petrel populations

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