Precise and nonscalar timing of intervals in a bird vocalization

Abstract

Animals can time their behaviours at predictable intervals. Their precision for doing so, however, may depend on the duration of the intervals. Laboratory experiments with animals show that timing precision decreases in proportion to the duration of the interval, a phenomenon known as scalar timing. In these experiments, animals are trained to wait for arbitrary intervals of time to get rewarded. In nature, animals time intervals as part of many stereotyped behaviours, regardless of whether the intervals are learned. It is unknown whether timing in this context is also scalar. Here, we tested for scalar timing in the song of the scaly-breasted wren, Microcerculus marginatus , which consists of whistles separated by intervals that increase in duration from less than 1 s to more than 10 s. We found that in nearly half of the songs, the timing of whistles was better explained by a model of constant precision rather than one of scalar timing. Moreover, in songs showing support for constant precision, the precision at the longest intervals was higher than that of nonhuman mammals and birds trained in the laboratory for timing presses at an operant device. The precision of the wren is also higher than that of humans, except when the latter count to increase their performance at timing. This study highlights the value of studying natural behaviours to uncover diverse strategies in interval timing among animals. • In Microcerculus marginatus songs, intervals increase from about 1 to 10 s in 0.5 s increments. • In many songs, the precision for timing intervals does not follow scalar timing. • Singing M. marginatus can be as precise as humans counting to time intervals. • Studying birdsong may reveal specialized neural mechanisms for precise timing.