Vocal, often detected by song. Pairs or small groups may sing simultaneously, either as a duet or loose chorus. Most common vocalization is a loud series of 15-20 accelerating clucks or "cuck" notes, each series 2-6 s in duration. Similar to song of White-tailed Trogon (T. viridis), but more nasal (less resonant), and faster in tempo, accelerating more towards the end of the series and often ending in a short clattering "cuk-cuk-cuk". Tempo and volume variable; song series sometimes accelerates to a crescendo and decelerates again, decreasing in volume. Pitch also may change abruptly, with one series of call notes immediately followed by another on a higher pitch. Skutch (1948: 138) reported that a vocalizing individual "jerks its tail up and down with rapid but mincing strokes and shakes its slightly relaxed wings". In duets, one bird begins an accelerating series of "cuck-cuck-cuck" notes and the second bird joins in with an overlapping series while the first bird is still calling (C. Riehl personal observations). Both sexes also vocalize alone. When excavating the nest cavity, pairs reported to produce "low, whining notes, which resemble the grunts of new-born puppies"(Skutch 1948: 138). Alarm call is a single low "cuck", often accompanied by a quick fanning of the tail. Begging nestlings give a continuous "far-away peeping, faintly audible a few paces from the nest" (Skutch 1948: 145).