Sexual selection is the cause behind the evolution of elaborate male ornaments in birds (e.g. the large comb and colorful feathers of a domestic chicken rooster). However, exactly how sexual selection works to produce such structures is not understood. Work to date indicates that the size of the comb and the degree of development of other ornaments of jungle fowl roosters (ancestors of domestic chickens) determine their sexual attractiveness to hens and their ability to dominate other roosters. Work to date indicates that ornaments are sensitive indicators of a male's resistance of disease. Thus the investigators have discovered l) a previously unknown relationship between health of males and ornamentation and 2) that sexual selection favors disease-resistant roosters. This first finding has important implications for the poultry industry since jungle fowl and domestic chickens are the same species. The disease resistance, by artificial selection on the basis of male ornaments, disease resistance, and sexual selection in the red jungle fowl.
