DISSERTATION RESEARCH: Functional Significance of Elaborate Plumage Characters when Expressed in both Sexes: A Case Study of the Turquoise-Browed Motmot (Eumomota superciliosa)

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Functional significance of elaborate plumage characters when expressed in both sexes: a case study of the turquoise-browed motmot (Eumomota superciliosa)Stephen T. Emlen - ProfessorTroy G. Murphy - Graduate StudentElaborate plumage is generally found in sexually dimorphic species of birds and is thought to be the product of sexual selection. When found in both males and females, this presents a paradox because females generally do not compete for access to males. Such elaborate, monomorphic characters may be products of natural selection acting equally on the sexes, or they may be products of mutual sexual selection acting equally on the sexes. The latter may occur in cases where both males and females compete for access to mates.This project is designed to test the adaptive function of extreme avian plumage elaboration when expressed equally in each sex. The focal species is the monomorphic and brilliantly plumed turquoise-browed motmot (Coraciiformes: Momotidae: Eumomota superciliosa) which breeds at colonial breeding grounds in Northern Yucatan, Mexico. Both males and females of this socially monogamous species have a number of equally exaggerated plumage characters, most notably of which is an elongate tail that terminates in large oval-shaped rackets that extend far below the body of the bird. This investigation will address whether the elaborate racket-tipped tail functions as a sexual signal used in competition for mates, or if it functions in a utilitarian context driven by natural selection. Five hypotheses for the function of the elaborate plumage will be tested using behavioral observations and experimental manipulations. Information gathered from this study will increase the scientific knowledge on the selective forces that maintain elaborate characters in monomorphic species.