Dual Utility of a Melanin‐Based Ornament in Bearded Tits

Abstract

A general mechanism to account for the maintenance of sexually selected traits is the armament–ornament model, which predicts that females exploit signals used in male–male aggressive contests. Melanin‐based ornaments are good candidates to be dual utility traits because they are usually involved in male–male competition and function as signals of male dominance or fighting ability. Despite this, very few studies have investigated the dual utility of melanin‐based plumage traits and results remain generally ambiguous. In this study, we investigated the dual function of a melanin‐based trait (the black beard) in the male bearded tit, Panurus biarmicus. In a controlled aviary experiment, beard length was the best predictor of dominance in male–male competition. In a choice experiment, females showed a proximity preference for males whose beard length was experimentally elongated. Our results indicate that beard length plays an important role in both male–male competition and female choice in bearded tits, as proposed by the dual utility model.

Wing whiteness as an indicator of age, immunocompetence, and testis size in the Eurasian Black-Billed Magpie (Pica pica)

“…Given that the quality of both parents influences reproductive success in the magpie (Birkhead 1991), the use of the same trait for information transfer under conditions of social monogamy can account for monomorphism when traits may convey information for both sexes (Jones and Hunter 1993, Kraaijeveld et al 2007, Hoi and Griggio 2008. Magpies are sexually dimorphic in wing whiteness, and both sexes show mate-choice behavior (Birkhead 1991).…”

The expression of melanin-based plumage is separately modulated by exogenous oxidative stress and a melanocortin

“…Hoi & Griggio 2008;Kingma et al 2008;McGraw 2008;Galván & Møller 2009). The honesty of these signals would be mediated by the relative cost that signallers experience during the trait production or during its maintenance (Hasson 1997;Alonso-Alvarez et al 2009).…”

UV plumage color is an honest signal of quality in male budgerigars

“…Many hypotheses try to answer the question: ''Why should individuals have a sexual preference for exaggerated or particular colored traits?'' Melanin-based ornamental colorations are under social control: in a number of species, melanin-based traits function as badges of social status (the ''status signalling hypothesis' ' Rohwer 1975;Senar 1999;Hoi and Griggio 2008). Moreover, recent studies suggest that melanins may not be as inexpensive to produce as initially thought, and so melanin-based traits can be honest signals (McGraw 2007).…”