trill, trilling, song, birdsong, cry, warbling, chirp, chirping, chirrup, chirruping, chirr, chirring, cheep, cheeping, twitter, twittering, tweet, tweeting, whistle, whistling, chatter, chattering, squeak, squeaking, pipe, piping, peep, peeping, call, calling.
EnglishOxford American Thesaurus
