Variable rate of singing and variable song duration are associated with high immediate early gene expression in two anterior forebrain song nuclei.

The duration of songs and the intervals between these songs are more variable when wild, adult, free-ranging chipping sparrows sing at dawn than when they sing during the day. The more variable delivery is used to interact with males, and the stereotyped delivery is used to attract females. In captive birds, however, the variability observed at dawn persists during the day. We quantified the expression of an immediate early gene, ZENK, in wild and captive birds and found that the level of song-associated ZENK expression in two song nuclei, Area X and lMAN, was positively related to variability in song duration and intersong interval and could be dissociated from the social context in which the song occurred. Thus, a combination of field and laboratory approaches helped us identify nuclei, context, and behavioral features associated with a change in gene expression thought to be a marker of behavioral variability.