Historical clue formulations

• Service with a bird logo — 2016-01-27
• Where many people may follow you — 2015-01-25
• Feed supplier — 2014-11-23
• See 20-Across — 2012-08-07
• Service with many followers — 2011-06-11
• Forum for 140-character messages — 2010-09-16
• Chirp rapidly — 2002-03-24