1) Bird talk 2) Cheep 3) Chirp 4) Chirrup 5) Peep 6) To twitter 7) Twirp 8) Twitter 
• (v. i.) To shiver or chatter with cold. • (v. i.) To chirp in a tremulous manner, as a bird.
Chit'ter intransitive verb [ Confer Chatter .] 1. To chirp in a tremulous manner, as a bird. [ Obsolete] Chaucer. 2. To shiver or chatter with cold. [ Scot.] Burns. 
[v] - make high-pitched sounds, as of birds
twitter verb make high-pitched sounds, as of birds
to twitter.