BIMODAL SIGNALING OF A SEXUALLY SELECTED TRAIT: GULAR POUCH DRUMMING IN THE MAGNIFICENT FRIGATEBIRD

Abstract

Abstract Female Magnificent Frigatebirds (Fregata magnificens) search for mates while flying and by visiting males at their display sites. Males respond with an intense courtship display that includes making a characteristic drumming sound and presenting the inflated gular pouch, a likely sexually selected trait. Viewing angle, male posturing, and proximity might, however, limit females' ability to appraise pouch size exactly. We investigated whether drumming provides the same information about pouch size and indeed found fundamental frequencies to be negatively correlated with estimated pouch sizes. Probably, the gular pouch functions as a resonance chamber. Females' assessment of gular pouch size could therefore be enhanced by the combination of visual and auditory signals. La Senalizacion Bimodal de un Atributo Seleccionado Sexualmente: El Sonido de la Bolsa Gular en Fregata magnificens Resumen. La busqueda de pareja en las hembras de Fregata magnificens incluye la inspeccion durante el vuelo y visitas...