Morphology and Ornamentation in Male MagnificentFrigatebirds: Variation with Age Classand Mating Status

Male magnificent frigatebird (Fregata magnificens) ornamentationincludes bright iridescent plumage and a red inflatablegular pouch. These signals are displayed during courtship, alongwith a drumming sound produced through specialized beak clackingsresonating in the gular pouch. The extent of white in theplumage identifies three age classes of nonjuvenile male. Here weinvestigate how morphological and secondary sexual traits correlatewith age class and mating status. Even though several age class-related differences in morphology and visual appearance can beidentified, the only features that significantly predict mating successare acoustic components of courtship display. Specifically, malesthat mate drum at lower fundamental frequencies