Not 100% sure on the species, there are multiple yellow-bellied kingbird species in the area that look very similar to each other. The Rio Grande Valley is home to many wonderful bird species and sometimes you'll see wild ones hang out at the zoo!
Unless you heard the bird call, the appearances of both the Tropical and Couch's Kingbirds are too similar and vary too much to positively identify this bird. Upon my visit I saw several kingbirds on zoo grounds and due to their refusal to vocalize I still can't determine which species they were.
