In Chinese culture crows traditionally have an unlucky association (a sign of death or bad news), opposite of magpies (
喜鹊) which signal good news. The character
鸦 =
牙 ('tooth', phonetic) +
鸟 ('bird'). The compound
乌鸦 (wūyā) is the modern everyday word for 'crow' —
鸦 alone is more literary.