White Flank Spots Signal Feeding Dominance in Female Diamond Firetails, Stagonopleura guttata

Abstract

Plumage colour can be used as an honest signal to convey health and status, which has traditionally been examined in the sexual selection context of choosy females and elaborate males. We use a model avian system to study the role of plumage coloration in a social context such as inter- and intrasexual competition over food resources. The diamond firetail (Stagonopleura guttata) is an endemic Australian finch: females have more white flank spots than males, and white spot number was correlated with cell-mediated immune response in females. We use two experimental designs to test the role of white flank spots for feeding dominance and dominance discrimination in a group-living bird. The results from two-choice trials and from single-arena trials showed that female ornamentation was consistently important in social food contests, and males consistently responded to female spot number. Females with higher spot number fed first, in trials with males and/or females. Also, females preferred to feed next to test birds with low spot number, but males showed no preference for feeding next to birds with few or many spots. Finally, latency to feed was predicted by spot number: both males and females had longer latency to feed if test birds had more spots than the focal birds. We conclude that female, but not male, ornamentation was important for inter- and intrasexual food competition. This is one of the very few studies to show that the same plumage ornament can have a different function between the sexes as a signal of social status. Moreover, this study shows that white plumage can be a signal of dominance

Migration and the evolution of sexual dichromatism: evolutionary loss of female coloration with migration among wood-warblers

“…Research has provided compelling evidence that the female ornamental phenotype is not under strong constraint due to genetic correlation and that female ornamental traits can change independently of male phenotype [9,10]. Such changes in female ornamentation have been inferred from recent research demonstrating female-specific functions of ornamentation in communication [11,12] and from comparative studies which have shown that female ornamental phenotype is evolutionarily labile, either becoming more or less exaggerated when compared with male ornamentation [5,10,13 -16]. A notable example comes from Martin and Badyaev's work, indicating that females evolve drabber plumage when they are subject to greater nest predation [6].…”

Costs and Benefits of Competitive Traits in Females: Aggression, Maternal Care and Reproductive Success

“…survival, offspring recruitment, attractiveness to males. Female expression of competitive traits may increase access to important resources in the non-breeding season [3], [79], [88], [92]–[96], which could strengthen the observed benefits of aggression. However, competitive traits can also have negative effects on survival [8], [14], [16].…”

Same trait, different receiver response: unlike females, male American goldfinches do not signal status with bill colour

“…social selection; West-Eberhard, 1979. Although much research has supported the role of signals of status among males (Griggio, Serra, Licheri, Monti, & Pilastro, 2007;Møller, 1987;Pryke & Andersson, 2003;Senar & Camerino, 1998), few examples of status signalling in females have been described (but see Coady & Dawson, 2013;Crowhurst, Zanollo, Griggio, Robertson, & Kleindorfer, 2012;Crowley & Magrath, 2004;Murphy, Hernández-Muciño, Osorio-Beristain, Montgomerie, & Omland, 2009;Murphy, Rosenthal, Montgomerie, & Tarvin, 2009;Swaddle & Witter, 1995). This male bias in research results is surprising given that both males and females of many species compete for access to mates or other resources (Tobias et al, 2012).…”