Movements of Pre-migratory Surf and White-winged Scoters in Response to Pacific Herring Spawn

Lok, Erika K.; Kirk, Molly; Esler, Daniel; Boyd, W. Sean

doi:10.1675/1524-4695-31.3.385

Cited by 17 publications

(13 citation statements)

References 22 publications

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“…Thus, marine lipid 5'^C values are not always more positive than those derived from freshwater food webs, and stable-isotope analyses alone may not be adequate for species with diverse diets. Scoters may feed on benthic marine resources when on the wintering grounds, although recent studies suggest that Pacific Herring spawn is an important source of nutrients for wintering and premigratory birds (Lewis et al 2007, Lok et al 2008. Obtaining stable-carbon-isotope values from scoters on marine spring staging areas would confirm whether or not lipid values are similar to those reported here for birds arriving on breeding grounds.…”

Section: Discussionsupporting

confidence: 66%

Combining Stable-Isotope and Body-Composition Analyses to Assess Nutrient-Allocation Strategies in Breeding White-Winged Scoters (Melanitta fusca)

DeVink

Slattery

Clark

et al. 2011

The Auk

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Birds meet the energy and nutrient demands of egg formation by using dietary (exogenous) sources, somatic (endogenous) nutrients, or combinations of both. Therefore, understanding plasticity in resource acquisition and the allocation strategies that are used is important for predicting how ecosystem changes across a species' range could affect vital rates. Sources of egg nutrients have traditionally been assessed through analyses of body composition, but stable-isotope analysis has provided a new tool in cases where animal tissues differ isotopically from the local food webs where they breed. We provide the first simultaneous comparison of these two techniques and test the "seasonally variable nutrient threshold hypothesis." Using body-composition analysis of Whitewinged Scoters {Melanitta fusca) collected at the northern extent of their range, we inferred that protein in rapidly developing ovarian follicles was derived entirely from dietary sources but that follicle lipids were most likely derived largely from somatic reserves. Stableisotope analysis confirmed that most protein was derived from dietary sources during early (70.7-86.6%) and late (83.4-94.4%) spring collection periods, but dietary lipids were not distinguishable isotopically from stored somatic lipids to estimate lipid contributions to eggs. This pattern dififered from that at the southern limit of the species' breeding range, where both lipid and protein for egg formation were derived from exogenous sources. Although our results were consistent with plasticity in resource-allocation strategies among sites (latitudinal variation), they did not support the seasonally variable nutrient threshold hypothesis within a site. We discuss the benefits of using both techniques simultaneously to assess reproductive strategies of birds that migrate between isotopically distinct areas. Une combinaison de l'analyse des isotopes stables et de celle de la composition corporelle pour évaluer les stratégies d'allocation des nutriments chez des individus reproducteurs de Melanitta fuscaRÉSUMÉ.-Les oiseaux comblent leurs besoins en énergie et en nutriments pour la formation des oeufs en utilisant des sources alimentaires (exogènes), des nutriments somatiques (endogènes) ou une combinaison des deux. Ainsi, comprendre la plasticité de l'acquisition des ressources et les stratégies d'allocation utilisées s'avère essentiel pour prédire la façon dont les changements écosystémiques à travers l'aire de répartition d'une espèce peuvent influer sur les paramètres démographiques. Les sources de nutriments pour les oeufs ont traditionnellement été évaluées par des analyses de la composition corporelle. L'analyse des isotopes stables constitue un nouvel outil pour les cas où les tissus des animaux diffèrent, sur le plan des isotopes, des chaînes alimentaires locales où ils se reproduisent. Nous fournissons la première comparaison simultanée de ces deux techniques et testons l'hypothèse d'un seuil des nutriments variable au cours de la saison. À l'aide d'une analyse de la composi...

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Section: Discussionsupporting

confidence: 66%

Combining Stable-Isotope and Body-Composition Analyses to Assess Nutrient-Allocation Strategies in Breeding White-Winged Scoters (Melanitta fusca)

DeVink

Slattery

Clark

et al. 2011

The Auk

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“…This means that variation in herring spawning timing and distribution may not constrain habitat use by highly mobile predators, such as scoters (Willson & Womble 2006). Pre-migratory surf scoters show increased movements in response to herring spawn at a local scale (Lok et al 2008) and are presumably capable of moving in search of spawn at larger scales, particularly during migration. We found that surf scoter migration generally coincided with the northward progression of herring spawn within the study years but did not follow the same pattern closely.…”

Section: Discussionmentioning

confidence: 99%

“…Marine birds are generally recognized to be responsive to spatial and temporal variation in prey availability (Weimerskirch et al 1994, Ainley et al 1996, Guillemette & Himmelman 1996, Hunt et al 1998, Litzow et al 2002, Žydelis et al 2006 and to adjust their foraging efforts and locations in response to ephemeral or novel prey (Marston et al 2002, Lewis et al 2007b, Lok et al 2008, Anderson et al 2009). However, to our knowledge, the present study is the first documentation of spatiotemporal relationships between migrating marine birds and the ephemeral and spatially fluctuating food resource represented by spawning marine fish.…”

Section: Discussionmentioning

confidence: 99%

“…During most of the year, scoters feed on bivalves and a variety of soft-bodied prey when in marine waters (Vermeer 1981, Anderson et al 2008. Along the Pacific coast, surf scoters are known to congregate and forage at herring spawning events during late winter and early spring (Vermeer 1981, Vermeer et al 1997, Sullivan et al 2002, Lok et al 2008. Proximity to herring spawn has been identified as a strong predictor of stopover habitat use (Lok et al 2011).…”

Section: Abstract: Habitat Use · Herring Spawn · Melanitta Perspicilmentioning

confidence: 99%

“…We considered a scoter location to be at a spawning event if the scoter was within 22 km of the centroid of an active spawning management section. The 22 km radius is based on the 95th percentile of mean interfix distances (the distance between subsequent locations) for VHF radio-fitted surf scoters in late winter when herring spawn was available (Lok et al 2008). Once we selected the data from scoters that spatially overlapped with the herring spawning event (i.e.…”

Section: Spawning Event Use Metricsmentioning

confidence: 99%

See 2 more Smart Citations

Spatiotemporal associations between Pacific herring spawn and surf scoter spring migration: evaluating a ‘silver wave’ hypothesis

Lok

Esler²,

Takekawa³

et al. 2012

Mar. Ecol. Prog. Ser.

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Stopover habitats of spring migrating surf scoters in southeast Alaska

et al. 2011

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Habitat conditions and nutrient reserve levels during spring migration have been suggested as important factors affecting population declines in waterfowl, emphasizing the need to identify key sites used during spring and understand habitat features and resource availability at stopover sites. We used satellite telemetry to identify stopover sites used by surf scoters migrating through southeast Alaska during spring. We then contrasted habitat features of these sites to those of random sites to determine habitat attributes corresponding to use by migrating scoters. We identified 14 stopover sites based on use by satellite tagged surf scoters from several wintering sites. We identified Lynn Canal as a particularly important stopover site for surf scoters originating throughout the Pacific winter range; approximately half of tagged coastally migrating surf scoters used this site, many for extended periods. Stopover sites were farther from the mainland coast and closer to herring spawn sites than random sites, whereas physical shoreline habitat attributes were generally poor predictors of site use. The geography and resource availability within southeast Alaska provides unique and potentially critical stopover habitat for spring migrating surf scoters. Our work identifies specific sites and habitat resources that deserve conservation and management consideration. Aggregations of birds are vulnerable to human activity impacts such as contaminant spills and resource management decisions. This information is of value to agencies and organizations responsible for emergency response planning, herring fisheries management, and bird and ecosystem conservation. © 2010 The Wildlife Society

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Movements of Pre-migratory Surf and White-winged Scoters in Response to Pacific Herring Spawn

Cited by 17 publications

References 22 publications

Combining Stable-Isotope and Body-Composition Analyses to Assess Nutrient-Allocation Strategies in Breeding White-Winged Scoters (Melanitta fusca)

Combining Stable-Isotope and Body-Composition Analyses to Assess Nutrient-Allocation Strategies in Breeding White-Winged Scoters (Melanitta fusca)

Spatiotemporal associations between Pacific herring spawn and surf scoter spring migration: evaluating a ‘silver wave’ hypothesis

Stopover habitats of spring migrating surf scoters in southeast Alaska

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