Possible Clues:

• Trilled like a bird
• Sang in hostilities, having suffered injury?
• Sang like a bird
• Wife wept after a rook trilled like a songbird
• Suffered wounds after fighting, but sang
• Sang with a quavering voice
• Sung of bleeding in battle
• Sang of those wounded 13 across
• Sang of battles, and showed injury
• Merrily they sang that fighting led to loss of blood