A region of the canary forebrain shrinks during the nonbreeding season and enlarges when breeding season begins. This change is probably associated with the annual A) addition of new syllables to a canary’s song repertoire. B) crystallization of subsong into adult songs. C) sensitive period in which canary parents imprint on new offspring. D) renewal of mating and nest-building behaviors. E) elimination of the memorized template for songs sung the previous year.