Related Clues:

• See 20-Across
• Chirrup
• A series of chirps
• Chirp
• Bird sanctuary excitement
• Palpitate
• Cheep
• Site with the tagline 'What are you doing?'
• Trendy social network
• Microblogging service
• Forum for 140-character messages
• Web phenomenon
• Social network
• Tweet source
• Site with tweets