I have exhausted my search: Audubon Field Guide and the internet. Anyone have an idea as to the identity of the Towhee's friend with its shades of brown and unusual light yellow on the forehead. Are certain kinds of sparrows this large and beautiful? I can't imagine.
Update: Thank you all for your help! Tina from In the Garden suggested that our mystery guest was a Golden-crowned Sparrow. As I continued in my attempt to verify, here is a photo I discovered by Dana Johnson; look at the comparison. Then, Corey at 10000 Birds site stated that it was a juvenile Golden-crowned Sparrow. What a grand community this is. Thank you.