California Quail (Callipepla californica) are the common quail of southern California. These cocks were calling in the brush around Carmel Valley Road, East of Carmel, April, 1999.
A cock Gambel's Quail (Callipepla gambelii) perches in the highest tree in his territory and issues this single note call. My Dad and I called this call the "nesting call" because we heard it continuously during the breeding and brooding season (May to July). My casual observations, though, now seem to indicate that this call is put out there by bachelor males advertising for a mate. I have not observed a cock who has a hen with him calling this way, nor have I heard a cock with young calling this note.
Gambels quail are heard the world over in every Western movie ever made. Here are two examples of their "gathering call" which you all knew, just didn't know you knew!