Sounds and Vocal Behavior

The Black-billed Nightingale-Thrush has a wide arrange of different vocalizations. The song has been described as similar to those of the Ruddy-capped Nightingale-Thrush Catharus frantzii (Ridgely and Gwynne 1989) or Russet Nightingale-Thrush Catharus occidentalis (Clement 2003), but thinner, higher and less musical. Stiles and Skutch (1989) describe the song as a series of two or three successive phrases, those differ among them in pitch, sounding fuzzy, and separated by a pause of some seconds.
Actually the song is more complex than previously described (e.g., ML 76570). Each song is composed of up to 8-18 song phrases, each phrase different from the one preceding; usually each song phrase has a different emphasized frequency, varying between one high pitched phrase and the next one with a lower pitch. Between each song phrase there is a pause of about 8 seconds, and between songs, pauses are longer than in between song phrases. Each song phrase lasts about 0.95 seconds.
The order of production of the song phrases is variable. The syntax of each song phrase also can vary highly between individuals, even among birds inhabiting the same population. Despite these differences, there is geographic structure in their song. In fact, the four geographically isolated populations of Costa Rica show significant differences in temporal and frequency characters (C. Sanchez unpub. data).
Generally males sing from perches within the understory, sometimes close to ground, and only rarely do they sing at higher levels in the forest. Males sing throughout the year, but the song output reaches a maximum during the breeding season, during which the songs are longer (larger number of song phrases) and are produced more often. It is commonduring the breeding season to hear males countersinging, so when one male starts a song, the neighboring males start singing back, producing a fine chorus. The intensity of song output during the breeding season suggest that this signal is related with territorial cues, as well as an advertisement for mate attraction, although, these hypothesis have yet to be tested for this species.
Other vocalizations are produced in a number of other contexts. One of the most frequent is a high pitch call with almost no frequency modulation, which is produced by both sexes during interactions between a pair. The alarm call (uttered, for example, in the presence of a potential) is composed of a number of short broadband pulses.

None reported.