Summary: Rivera-Gutierrez et al. (2010)

Birdsong, a multifaceted signal consisting of many traits (each under sexual selection pressure), plays an important role in both female mate choice and male-male competition. 3 hypotheses have been proposed to explain the expression of these traits: 1) one trait signals one aspect of male quality, therefore many traits represent a multidimensional message (multiple-messages hypothesis); 2) each trait signals only partial information, therefore many traits signal redundant information (redundant-signal hypothesis); 3) traits do not provide reliable information about male quality but are retained because they are not costly to produce (unreliable-information hypothesis). Rivera-Gutierrez et al. (2010) investigated whether the various components of song of 58 great tits (Parus major) was expressed differently in relation to 3 indicators of male quality (age, condition survival). They found support for all 3 hypotheses, concluding that great tit song is a multidimensional signal conveying multiple, redundant and unreliable information about male quality.