Salt Lake Tracts Professional Review and Guide
"The Lower Rio Grande Valley National Wildlife Refuge owns several tracts of unique wetland habitat north of Texas Highway 186 east of its intersection with US 281, about 18 miles north of Edinburg. At the heart of these tracts are hypersaline (i.e., very salty) lakes, with a long history of exploitation for their mineral content. (That use continues today: Though the U.S. Fish and Wildlife Service owns the land, commercial interests still hold mining rights, extracting brine from the lakes.)
The whole area is a closed basin, and the hydrology of the lakes is not fully understood by geologists. Although the areas are mostly undeveloped and not as easy to access as many sites, they’re very popular with local birders for migrant and wintering waterfowl, Sandhill Cranes, and shorebirds as well as “western ” birds attracted to the arid, scrubby environment."