At South Padre Island convention center, there is an area that has been created for migrating birds. It has water features and trees and shrubs. There is also a boardwalk that extends out over the marsh that is hundreds of feet long. From here you can see rails and shorebirds. This is one of the most incredible birding spots we have been to. We saw over 100 different species the day we went here.
The birding here is phenomenal. Below is a picture of the convention center with black bellied whistling ducks lined up on top.