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Swaddle, J.P.; Witter, M.S. |
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Title |
Chest Plumage, Dominance and Fluctuating Asymmetry in Female Starlings |
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Year |
1995 |
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Proceedings of the Royal Society B: Biological Sciences |
Abbreviated Journal |
Proc. Roy. Soc. Lond. B Biol. Sci. |
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260 |
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1358 |
Pages |
219-223 |
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Abstract |
It has been proposed that levels of fluctuating asymmetry (FA) may be used in establishing and maintaining dominance hierarchies, as asymmetry reflects aspects of individual quality. However, previous manipulations of FA have failed to reveal that the level or outcome of agonistic intra-sexual interactions are affected by levels of FA. In female European starlings (Sturnus vulgaris), correlational data suggest that FA of the speckled chest plumage may be related to dominance status. These data are confounded, however, by total number of spots on the chest and the proportion of the chest that is white, both of which positively covary with chest asymmetry. Thus, we deconfounded the effects of these plumage traits on dominance by experimentally manipulating the number of spots and spot number asymmetry in a factorial design. The results indicated that dominance is influenced by the number of spots on the chest, but not by spot asymmetry. Birds with spottier chests were dominant over birds with experimentally decreased spot number. We suggest that female starlings' chests are exposed to extensive abrasion throughout the breeding season and so are susceptible to damage asymmetries that may mask the `true' fluctuating asymmetry of the trait. This may devalue the use of chest asymmetry as a quality indicator. Spottier chests may be costly to maintain, in part because of increased susceptibility to abrasion, and so may be a better indicator of quality than asymmetry. |
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Equine Behaviour @ team @ |
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2202 |
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Author |
Witter, M.S.; Swaddle, J.P. |
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Title |
Fluctuating Asymmetries, Competition and Dominance |
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Journal Article |
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Year |
1994 |
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Proceedings of the Royal Society B: Biological Sciences |
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Proc. Roy. Soc. Lond. B Biol. Sci. |
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256 |
Issue |
1347 |
Pages |
299-303 |
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Levels of fluctuating asymmetry (FA) in the primary feathers of European starlings, Sturnus vulgaris, have been shown to be sensitive to nutritional and energetic stress. Furthermore, between-individual variation in plumage FA has been found to be related to social dominance, even without social interactions during feather growth, with dominant birds exhibiting the highest levels of FA. Here we examine whether the relation between dominance and FA differs when birds are housed in social groups, under different degrees of competition for food, during moult. We reason that dominants should derive a greater benefit from their social status as competition for food increases. Our results support this proposition. The relation between dominance and FA differed significantly according to the degree of competition for food. However, in no cases did the dominants exhibit lower levels of FA than subdominants. When competition for food was low, dominants had higher levels of FA than subdominants. When competition for food was high, there was no systematic relation between dominance and FA. These results suggest that dominants may only derive a net benefit from their social status, under the circumstances of our experiment, during severe conditions of competition. |
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Equine Behaviour @ team @ |
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2203 |
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Hunt, G.R.; Gray, R.D. |
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The crafting of hook tools by wild New Caledonian crows |
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2004 |
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Proceedings of the Royal Society B: Biological Sciences |
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Proc. Roy. Soc. Lond. B Biol. Sci. |
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271 |
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S88-S90 |
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The 'crafting' of tools involves (i) selection of appropriate raw material, (ii) preparatory trimming and (iii) fine, three-dimensional sculpting. Its evolution is technologically important because it allows the open-ended development of tools. New Caledonian crows manufacture an impressive range of stick and leaf tools. We previously reported that their toolkit included hooked implements made from leafy twigs, although their manufacture had never been closely observed. We describe the manufacture of 10 hooked-twig tools by an adult crow and its dependent juvenile. To make all 10 tools, the crows carried out a relatively invariant three-step sequence of complex manipulations that involved (i) the selection of raw material, (ii) trimming and (iii) a lengthy sculpting of the hook. Hooked-twig manufacture contrasts with the lack of sculpting in the making of wooden tools by other non-humans such as chimpanzees and woodpecker finches. This fine, three-stage crafting process removes another alleged difference between humans and other animals. |
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refbase @ user @ |
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3526 |
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