Until today, I was really starting to think I was an idiot for missing Henslow's Sparrows this year. Well, a walk at Red Feather Prairie this morning solved that; there were at least 3 singing Henslow's. Here is one:
Here is a map of Red Feather Prairie and the area that I found the Henslow's:
View Red Feather Prairie in a larger map
Stopping at a reliable BELL'S VIREO spot two miles from my house was successful: