Visual and song nuclei correlate with courtship skills in brown-headed cowbirds

We assessed courtship success in 14 adult male brown-headed cowbirds, Molothrus ater. Volumes of song control nuclei and visual nuclei were measured in Nissl stained tissue. Variation in courtship success was found to be related to variation in two areas of the avian brain: the song control nucleus, area X, and the thalamic visual area, nucleus rotundus. Volume of area X was negatively correlated with song potency, as assessed by female playback, and with rate of vocalizing. Volume of nucleus rotundus was positively correlated with song potency, vocalizing to females and courtship persistence. These data are the first to implicate a visual nucleus in the use of song. The data also complement previous findings with cowbirds suggesting that song learning involves visual attention to females. Taken as a whole, these results suggest that use of song depends on integration of auditory, vocal and visual information. In that female songbirds in many species assess multimodal performance of song, these findings with cowbirds suggest that future studies of brain and behaviour include a broader view of possible behavioural and neural correlates. (C) 1998 The Association for the Study of Animal Behaviour.