Passing by.
This is a western cattle egret (Bubulcus ibis). I keep meaning to get out and go find some of these in the pastures or rice fields, but so far haven't gotten around to doing that. A problem might be that usually when I've seen them, I'm driving by on a highway with nowhere to pull over.
"To find Western Cattle Egrets, head to agricultural areas near wetlands. These are tropical herons, so your best chances will be in warm parts of the southern U.S. Seeing cattle egrets is not difficult once you find the right habitat—they usually walk around in the open, on dry land, as they hunt grasshoppers and other small animals. True to their name, cattle egrets often associate with cows and other large farm animals, waiting to strike until the cow disturbs an insect or frog. Sometimes, cattle egrets even stand atop cows and horses, making them both easy to spot and easy to identify." - allaboutbirds.org