There were several errors published in J. Exp. Biol.212, 2411-2418.

Fig. 3 showed incorrect means and standard errors. The correct version of Fig. 3 is published below.

In addition, in Table 1, the estimates and standard errors for analyses 10, 11, 12, 13 and 14 should be multiplied by 0.467, 0.937, 0.120, 0.467 and 0.467, respectively. These errors resulted from the incorrect calculation of the volumes of the song-control nuclei. Because the same calculation error was made for every measurement, regardless of experimental treatment, none of these corrections affect the z-scores or P values, and, therefore, this correction does not influence any of the publication's results or conclusions.

The authors apologize for any inconvenience caused by these errors.