Quantifying song bout production during zebra finch sensory-motor learning suggests a sensitive period for vocal practice

Abstract

Using an event-triggered recording system, the quantity of daily song bout production was measured weekly in male zebra finches (Taeniopygia guttata) during sensory-motor learning and at one year of age. Our aim was to ask whether the development of a stereotyped vocal pattern involves a practice-driven component. If so, we hypothesized that juvenile males learning song should sing more often than adults reciting a vocal pattern they had already learned, and that greater levels of juvenile singing should be associated with improvement in the quality of the adult song. Across the period measured (36-365 days of age), subjects showed an inverted U-shaped pattern of daily song bout production. Song bout production was lowest during subsong, with increased production associated with plastic song and song crystallization, although individual differences were large. Daily song bout production decreased in adulthood. Higher levels of song bout production during plastic song correlated with fewer sequencing errors in adult song patterns (r(2)=0.77). In contrast, quantity of singing during song crystallization showed no relationship to vocal stereotypy (r(2)=0.002). Our data suggest a sensitive period for vocal practice during zebra finch sensory-motor learning with consequences for the note-sequence fidelity of the adult vocal pattern.

Fig. 1

The within-day pattern of undirected song bout production during sensory-motor learning and in adulthood (14:00-h light:10:00-h dark cycle). Data are the mean number of song bouts produced every 2 h (+S.E.) by a group of birds (n=5) recorded for 24 h at 36, 42, 49, 56, 63, 70, 77, 84, 91, 112, and 365 days of age. During subsong and plastic song, birds showed distinct morning and evening peaks of song bout production, whereas singing during song crystallization and in adulthood tended to be organized in a single diurnal peak.

Fig. 2

The number of undirected song bouts produced per day shows an inverted U-shaped pattern across vocal development. Data are the mean number of song bouts produced per day (−S.E.) by a group of birds recorded for 24 h at 36, 42, 49, 56, 63, 70, 77, 84, 91, 112, and 365 days of age. Daily song bout production was significant higher during plastic song and song crystallization than during subsong or in adulthood. An extrapolation of these data suggests that on average, male zebra finches produce well over 50 000 bouts of undirected song during vocal development.

Fig. 3

Song bout duration is relatively stable across vocal development. Data are the mean song bout duration (−S.E.) produced by a group of birds recorded for 24 h at 36, 42, 49, 56, 63, 70, 77, 84, 91, 112, and 365 days of age. Ten song bouts were randomly selected and measured from each subject at each age to generate means. The song bout duration of birds at 365 days of age was significantly longer than at 36 days of age.

Fig. 4

Cumulative undirected song bout production recorded during plastic song (A), but not during song crystallization (B), is related to the note-sequence fidelity of the crystallized vocal pattern. Data are the total number of song bouts recorded from individual birds (n=8) during plastic song (A, four 24 h recordings), or during song crystallization (B, four 24 h recordings), as a function of the stereotypy score of the vocal patterns recorded at the end of song crystallization (112 days of age). See text for details on how stereotypy scores were measured.