CHEST PLUMAGE, DOMINANCE AND FLUCTUATING ASYMMETRY IN FEMALE STARLINGS

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.