I grabbed my Sibley's Guide to Bird life and Behavior and it says that all
the Ammodramus sparrows will typically dive back into the grass when
spooked. That includes most of the ones that Ms Sparrow, I mean Bonnie,
mentioned. It also includes Baird's, both sharp-tails and seaside, but not
Savannah, which is a Passerculus. So it appears that there could be 7, maybe
8 candidates, if we include the Savannah.
    Jerry