Look for Swainson's Warbler on the ground in dense undergrowth. The main body of migrants pass though in the first half of April.
Swainson's Warbler breeds in the east Texas woods south to about Houston. It might be easier to find on the nesting grounds in late April and May when it is singing. Look for migrating Swainson's Warblers at at San Bernard NWR, at High Island, and the T.O.S Sabine Woods.
A breeding range map is available form the Breeding Bird Survey