Correlation between the size of song control nuclei and plumage color change in orange bishop birds

Adult male orange bishop birds (Euplectes franciscanus) develop beautiful nuptial plumage during the breeding season, but have the same sober plumage as the female during the non-breeding season. The male conspecific song is highly stereotyped during nuptial plumage. Large volume differences were found in two song control nuclei in the cerebrum between the male and female during the breeding season, and in the same nuclei of the males during the breeding and non-breeding seasons. The seasonal changes in the size of cerebral song control nuclei were dominant in the male and may not correlate with the improvement or modification of the song repertories.