Dominance in feeding territories relates to foraging success and offspring growth in brown skuas <Emphasis Type="Italic">Catharacta antarctica lonnbergi</Emphasis> |
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Authors: | Steffen Hahn Silke Bauer |
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Institution: | (1) Institute of Ecology, Friedrich-Schiller University Jena, Dornburger Strasse 159, 07743 Jena, Germany;(2) Centre for Limnology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 1299, 3600 BG Maarssen, The Netherlands;(3) Present address: Swiss Ornithological Institute, 6204 Sempach, Switzerland |
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Abstract: | Territoriality should lead to strict dominance, as territory holders typically control access to resources and exclude others
from their use. In feeding territories, dominance should be reflected in foraging success and ultimately in reproduction differences;
however, these successive links have rarely been made explicit. Therefore, we investigated a population of brown skuas Catharacta antarctica lonnbergi, in which only part of the breeding population occupied feeding territories within penguin colonies. We identified the dominance
hierarchy and determined the foraging success of the participants in fights for access to penguin carcasses within the territories.
Furthermore, we monitored offspring growth from parents with and without feeding territories. Our results indicated a clear
dominance hierarchy with territorial birds in their own territory dominating over territorial breeders from other territories,
non-territorial breeders and non-breeding birds. However, territory owners could not completely exclude others from access
to food. Foraging success was positively related to dominance scores: The dominant territory owners received 63% of a carcass,
whereas non-territorial pairs could get less than 10%. The link between foraging success and offspring development was less
clear: Although male chicks of non-territorial parents suffered from lower growth rates and, thus, delayed fledging, there
were no such differences in female chicks. Territoriality in skuas did not imply a complete occupation of food, but guaranteed
optimal growth conditions for offspring. Non-territorial individuals were forced to search for alternative resources, and
the restricted access to the preferred food resulted in inferior conditions for offspring development, making this foraging
strategy less rewarding. |
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Keywords: | Territorial fights Aggression Territoriality Dominance hierarchy Growth trajectory Seabird |
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