chirp

Concise Oxford English Dictionary © 2008 Oxford University Press:
chirp/tʃɜːp/

▶verb

• 1 (of a small bird or a grasshopper) utter a short, sharp, high-pitched sound.

• 2 say something in a lively and cheerful way.

▶noun a chirping sound.

– derivatives
chirper noun.

– origin ME: imitative.