Jp. Swaddle et Ms. Witter, CHEST PLUMAGE, DOMINANCE AND FLUCTUATING ASYMMETRY IN FEMALE STARLINGS, Proceedings - Royal Society. Biological Sciences, 260(1358), 1995, pp. 219-223
It has been proposed that levels of fluctuating asymmetry (FA) may be
used in establishing and maintaining dominance hierarchies, as asymmet
ry reflects aspects of individual quality. However, previous manipulat
ions of FA have failed to reveal that the level or outcome of agonisti
c intra-sexual interactions are affected by levels of FA. In female Eu
ropean starlings (Sturnus vulgaris), correlational data suggest that F
A Of the speckled chest plumage may be related to dominance status. Th
ese data are confounded, however, by total number of spots on the ches
t and the proportion of the chest that is white, both of which positiv
ely covary with chest asymmetry. Thus, we deconfounded the effects of
these plumage traits on dominance by experimentally manipulating the n
umber of spots and spot number asymmetry in a factorial design. The re
sults 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 sug
gest that female starlings' chests are exposed to extensive abrasion t
hroughout the breeding season and so are susceptible to damage asymmet
ries that may mask the 'true' fluctuating asymmetry of the trait. This
may devalue the use of chest asymmetry as a quality indicator. Spotti
er chests may be costly to maintain, in part because of increased susc
eptibility to abrasion, and so may be a better indicator of quality th
an asymmetry.