Multiple ornaments and sexual selection in a passerine bird: the Serin (#429)
A wide range of animals have more than one sexual ornament and much attention has been devoted to understand how they evolved. Frequently, birds exhibit simultaneously, a large variety of acoustic and visual ornaments, providing a multiplicity of signals with informative content. The Serin, Serinus serinus, is a small monogamous sexually dimorphic passerine bird, where males court females singing and exhibiting their colouration. It has been shown that song and colouration are involved in mate choice in serins, as females showed preference for higher frequency songs and for more colourful males. In order to understand if these traits signals the same qualities of individuals and the extent to which ornament expression reflects individual condition and behaviour, we studied the relationship between song and colouration and indicators of male quality: body condition, body size, beak size, immune capacity (PHA-P) and physiological response to stress (breath rate). We found that song and colouration measurements seem to be signaling different quality traits, where colour saturation predicted body condition, whereas maximum song frequency predicted body size. Our findings meet the multiple message hypotheses, and suggest that multiple ornaments may convey information on different aspects of male quality.