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.
Douglas Von Gausig (recordist; copyright holder), Naturesongs.com
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