Very cool to see so many people that know something about birds on here!

I'm going to go with Crested Caracara (also known as Mexican Eagle). They are pretty cool birds, and I saw my first Caracaras in TX (Brownsville area).

They do hang out with "buzzards" (Turkey & Black Vultures). Another bird that hangs out with buzzards is the Zone-tailed Hawk, which is a possibility in your area as well. However I'd be willing to bet this bird was a caracara.

I personally use Sibley's; it's suitable for birders just beginning to those more advanced; however, it is BIG and in Texas you'd need the "big" one rather than eastern or western.

National Geographic is a good guide too, but I like Sibley's better.