Meeting Abstract
Animals often time their behavioral displays with precision. Sometimes, they change the tempo of the display in a single session, as some southern nightingale-wrens (Microcerculus marginatus) do with their songs. In these songs, the tempo is slowed down due to a progressive increase in the lengths of silence intervals between syllables. The first interval lasts around 0.7 seconds, while the last interval may reach 12 seconds. By analyzing several songs downloaded from the database Xeno-Canto, we found that a simple pattern describes the increase in interval duration. The duration of a given interval was equal to that of the preceding interval plus a time constant. For example, in a single rendition, a bird added 0.6 seconds of silence to each consecutive interval, even when the preceding interval was already more than 10 seconds long. The timing of the intervals did not seem to follow Weber’s law, because the time constant was precisely kept despite increasing silence intervals. It is unknown how nightingale-wrens achieve this remarkable degree of precision in timing. Not all nightingale-wrens, however, change the tempo of their songs; songs vary considerably across populations. Geographic song variation in oscine passerines, such as the Nightingale-Wren, is often a by-product of vocal learning. If the same applies to southern nightingale-wrens, then the change in tempo in some populations may be at least partly learned.
