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Landscape features and sea ice influence nesting common eider abundance and dispersion

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Abstract:

Factors that influence individual and colony spacing are still not well understood in many organisms. Common eiders (Somateria mollissima (L. 1758)) nest on coastal islands and forage in intertidal and shallow subtidal waters. We considered several biotic and abiotic factors, their interactions, and how these might influence the distribution of eider colonies at several spatial scales in Labrador, Canada. At the island level, nest abundance was not related to intertidal prey density. At the 104km2 grid scale, eider nest abundance and the coefficient of dispersion (CD; the variance to mean ratio of colony size or grid cell, where CD indicates population dispersion) were negatively related to the number of islands. Spring ice cover was positively related to the number of islands but was negatively related to eider nest abundance and to CD. Ice cover – abundance and ice cover – CD were significant at two spatial scales (104and 455km2, respectively), but other relationships were weaker at the larger spatial scale. We hypothesize that during the spring, archipelagos with many islands trap ice, providing terrestrial predators access to nesting islands by acting as bridges and that increased predation reduces habitat quality causing nesting eiders to disperse. Our findings suggest that eiders respond to landscape features, including ice cover, a feature that is being influenced by climate change.

Les facteurs qui influencent l’espacement des individus et des colonies restent encore mal connus chez de nombreux organismes. Les eiders à duvet (Somateria mollissima (L. 1758)) nichent sur des îles côtières et se nourrissent dans la région intertidale et les eaux peu profondes de la zone subtidale. Nous avons examiné plusieurs facteurs biotiques et abiotiques et leurs interactions afin de voir comment ils peuvent influencer la répartition de colonies d’eiders à différentes échelles spatiales au Labrador, Canada. À l’échelle des îles, la densité des nids n’est pas reliée à la densité des proies de la zone intertidale. À l’échelle d’une grille de 104 km2, l’abondance des nids d’eiders et le coefficient de dispersion (CD, soit le rapport variance à moyenne de la taille de la colonie ou cellule de la grille qui représente la dispersion de la population) sont en relation négative avec le nombre d’îles. La couverture de glace au printemps est en corrélation positive avec le nombre d’îles et en corrélation négative avec l’abondance des nids d’eiders et avec CD. Les relations de la couverture de glace – de l’abondance, ainsi que de la couverture de glace – de CD sont significatives à deux échelles spatiales (104 et 455 km2, respectivement), mais les autres relations deviennent plus faibles à l’échelle spatiale plus grande. Nous émettons l’hypothèse selon laquelle, durant le printemps, les archipels composés de plusieurs îles emprisonnent la glace, ce qui donne accès aux prédateurs terrestres en formant des ponts vers les îles de nidification; la prédation accrue réduit la qualité de l’habitat, forçant la dispersion des eiders en nidification. Nos résultats indiquent que les eiders réagissent aux caractéristiques du paysage, en particulier à la couverture de glace, une caractéristique qui est sous l’influence du changement climatique.

Document Type: Research Article

Publication date: March 1, 2007

More about this publication?
  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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