Sounds

Usually silent, calling only when coming in to land, in display, and when begging for food. Accounts of specific calls often inconsistent, and certainly incomplete; much remains to be done in describing and characterizing vocal behavior in this species, and in interpreting the function and context of calls.

No sonagraphic studies have been made, and nothing is known about geographic variation in vocal behavior.

Development

Little information; chicks give a distinctive food-begging call (see Vocal array, below), and the arrival call of flying juveniles is harsher than that of females. No information on when or how male song is acquired.

Vocal Array

Most completely described in males, but not clear to what extent main sounds are vocal versus mechanical (i.e., produced by mandibles; Cramp and Simmons 1977). Most information and quotations from Diamond 1973, at Barbuda, e. West Indies.

Female occasionally gives a rapid twittering, accompanied by vibration of the bill, after landing near a displaying male; probably same as ‘rattling’ recorded from females by van Tets (1965).

The following calls also described but relationship with above array is not clear: ‘grating cry’ by males fighting in air above colony (Eisenmann 1962); resonant ‘gurgling’ or ‘chuckling’ calls by both sexes during courtship (Murphy 1936; possibly confused with Great Frigatebird in same colony); ‘chirping’ calls of young (Murphy 1936).

Phenology

Male songs restricted to courtship period; may continue during nest-building but cease once egg laid.

Daily Pattern

On Barbuda, e. West Indies, songs most frequent around sunrise, declined to minimum about 4 h later; rose steadily thereafter to frequency at sunset about half that at sunrise; some songs heard after dark. Data from parts of 2 d only, so unlikely to be fully representative.

Places Of Vocalizing

Display songs, and female ‘twittering’, confined to communal display sites of males, at which nests are later built. Arrival calls given also at roosts.

Repertoire And Delivery Of Songs

No studies of how songs vary within or among males, or of vocal differences among populations.

Social Context And Presumed Functions Of Songs

Restricted context of male songs—given only from communal display sites—strongly suggests a sexual function of attracting females. See also Vocal array, above.

Rapid vibration of the bill accompanies all 3 male songs, and adults of both sexes snap the bill when lunging at intruders. Hungry young may Bill-clatter (snapping mandibles together loudly) to attract parents (Eisenmann 1962).