Carotenoid status signaling in captive and wild red-collared widowbirds: independent effects of badge size and color

Carotenoid-based plumage ornaments are typically consideredto be sexually selected traits, functioning as honest condition-dependentsignals of phenotypic quality, but few studies have addressedthe function of carotenoid color variation in male contestcompetition. Using two experiments, we investigated the statussignaling function of the variable (ranging from yellow tored) carotenoid throat patch (collar) in the polygynous, sexually dimorphic red-collared widowbird (Euplectes ardens). First,we tested if the red collar functions as a dominance signalby painting spectrometrically controlled collar patches ontothe brown plumage of nonbreeding males and staging dyadic malecontests over food resources. Red-collared males dominatedorange males, which in turn dominated the control brown andnovel blue collars. Red dominance persisted when the collar manipulations were reversed within dyads and also when testedagainst testosterone implanted males. In the second experimentthe collar size and color of breeding males were manipulatedin the field before and after territories were established.All males with enlarged red and most with enlarged orange orreduced red collars obtained territories, whereas most maleswith reduced orange and all with blackened (removed) collarsfailed to establish or retain territories. In addition, amongthe territorial males, those with reduced signals defendedsmaller territories, received more intrusions, and spent moretime in aggressive interactions. Redness and, to a lesser extent,size of the carotenoid ornament both seem to independently indicate male dominance status or fighting ability in male contest competition.