Verdin

Bigger than a bread box?  (Remember bread boxes and that saying?  We used it when we played 20 questions).
No, it isn't.  Bigger than a hummingbird and Lesser goldfinch but considerably small than other finches, they have a loud, distinctive call. Read more about them here., where you can also view a range map and click on the sound tab to hear one.  I love these unique little fellows.  I am so fortunate to have oodles of them come to my yard.