Possible Clues:

• Comment in 140 characters or fewer
• Social media nugget
• Message limited to 140 characters
• High-pitched sound
• Sentimental time for bird sound
• Message that might include an '@' and a '#'
• In the middle of battle there's little bird song
• ... online message from number one in road racing event
• There's little in the sound of the little bird
• Brief communication