Those Black-crested Titmice seen foraging in the Sweet Acacias look, sound and behave pretty much like the Tufted Titmice so common at birdfeeders in eastern North America. In fact, sometimes Black-crested Titmice have been regarded as a subspecies of Tufted Titmice, but now usually they're considered to be a distinct species, one favoring more arid woodlands than the Tufteds.
The most obvious difference between the two species is that the front part of the Black-crested Titmouse's crest is perfectly black, while the Tufted's tuft is all gray. You can see the black-fronted tuft at http://www.birdphotography.com/species/bcti.html.
Black-crested Titmice are distributed from Texas and southern Oklahoma into east-central Mexico -- to HERE.