Dear Bird Correspondent

Dear Bird Correspondent, I was entering the backyard when I heard a loud and persistent birdcall that sounded like a machine gun: CHUCKACHUCKACHUCKACHUCKACHUCK! I walked up to the bush from which the sound was emanating and I saw a VERY TINY LITTLE BIRD that one could hardly expect to make such a loud noise. But that's what it was doing! This extremely small bird was greenish and goldish. It was a rapid flyer but not especially skittish. What was this bird, dear bird correspondent, pray tell?