Only Nelson's Sharp-tailed Sparrow is known to winter in Texas.
All sharp-tailed sparrows have buffy checks and breast with a white belly. A central gray crown stripe distinguish it from Le Conte's Sparrow (white central stripe).
The Saltmarsh Sharp-tailed Sparrow has a distinct gray ear patch. Nelson's has a very diffuse ear patch making it look more like a Le Conte's Sparrow. Check the crown stripe.
They are secretive birds, running on the ground instead of flushing. They respond to "pishing", but be ready they will only pop up for a moment.
Sharp-tailed Sparrows inhabit saltmarshes, often in the spartina grass and share the habitat with Seaside Sparrows and Le Conte's Sparrows.
The best place for Sharp-tailed Sparrows I know is the Bolivar Flats Bird Sanctuary. Go to the end of the beach where the spartina grass starts.
A breeding range map is available form the Breeding Bird Survey
A winter range map is available from the Christmas Bird Count