I’m unsure as to why or how, but my cat has different chitters for each type of bird or creature that he’s watching. The volume is also dependent on the size of the creature, so sparrows get a decently quiet “ch-ch-ch” sounds, while crows get a louder more crow-like “cha” sound.

The morning that he was making really loud unusual chirping was the morning that there was a set of vultures on the neighbors roof that he was watching.

Usually, though, I can reasonably identify the bird even if I’m in a different room.