Seasonal activation and inactivation of song motor memories in wild canaries is not reflected in neuroanatomical changes of forebrain song areas

Seasonal, testosterone-dependent changes in sexual behaviors are common in male vertebrates. In songbirds such seasonal changes occur in a learned beh avior-singing. Domesticated male canaries (Serinus canaria) appear to lose song units (syllables) after the breeding season and learn new ones until t he next breeding season. Here we demonstrate in a longitudinal field study of individual, free-living nondomesticated (wild) canaries (S. canaria) dif ferent mode of seasonal behavioral plasticity, seasonal activation, and ina ctivation of auditory-motor memories. The song repertoire composition of wi ld canaries changes seasonally: about 25% of the syllables are sung seasona lly; the remainder occur year-round, despite seasonal changes in the tempor al patterns of song. In the breeding season, males sing an increased number of fast frequency-modulated syllables, which are sexually attractive for f emales, in correlation with seasonally increased testosterone levels. About 50% of the syllables that were lost after one breeding season reappear in the following breeding season. Furthermore, some identical syllable sequenc es are reactivated on an annual basis. The seasonal plasticity in vocal beh avior occurred despite the gross anatomical and ultrastructural stability o f the forebrain song control areas HVc and RA that are involved in syllable motor control. (C) 2001 Academic Press.