This green heron (Butorides virescens) was spotted along Lady Bird Lake. Unlike other herons, the green heron has short legs and is stocky. Because of their short legs, they are known to stay at the water’s edge and hunt for fish and amphibians. In comparison to other herons, the green heron will wade less, staying on vegetation or solid ground. They are sometimes known to use certain materials to lure their fish prey. This species resides primarily in North and Central America.
My iNaturalist observation can be found here.
Sources: http://www.inaturalist.org/taxa/5020-Butorides-virescens; https://www.allaboutbirds.org/guide/Green_Heron/id