初音（はつね）:その年の初めに鳴く鳥の声のこと。初声。特にうぐいすをさす。その声を聞けば、春の訪れを感じることから「春告鳥」とも。

Hatsune: The sound of birds chirping at the beginning of the year. First sound. Especially refers to the nightingale. If you hear its voice, you can feel the arrival of spring, so it is also known as the "Spring Bird".