Work in progess-we will be adding additional information.
The flight call when at the breeding site is a loud series of short, high raspy notes, best described as keck keck keck, delivered in rapid succession. This vocalization is used by both paired birds as a greeting when one flies to a nest already occupied by its mate or when a bird is disturbed at the nest. Another call at the breeding site is an extended high-pitched kreeee used to initiate courtship flight. Adults emit a shrill scream when in conflict with other birds, Red-Billed or White-tailed, and when being removed from the nest (MWM and DSL per. obser.). Adult vocalizations have been described as two distinct call notes (Gosse 1847). One is like that of a gull, the other a trill chattering rattle like the boatswain's ("bosun's") whistle giving the species its common name among sailors, Boatswain Bird. Boatswain Island was actually named after the Red-billed Tropicbirds nesting there. Newly hatched chicks utter soft peeps. Adults cluck softly when they come to the nest to feed their chicks. The chicks respond with soft chirps until the food has been delivered. As the chicks develop the peeps are replaced by the keck keck keck of the adults. Hatchlings peep when handled. Adults, nestlings and fledglings issue the keck keck keck alarm call when approached closely and will switch to a scream followed by a painful bite with their serrated bills when first handled. However, birds at a study site on Saba quickly acclimated to being removed from nests for weighing, measuring and banding and no longer screamed when removed from the nest (MWM and DSL pers. observ.). Birds away from breeding sites are usually much less vocal, but do vocalize even when far at sea and outside the nesting period.