I know this is a Whiskered Screech Owl because its trainer at the Arizona-Sonoran Desert Museum said so. That helps a lot since the major distinction from the Western Screech Owl is its voice which is a series of short whistles all of the same pitch while the voice of the Western Screech Owl is a series of short whistles accelerating in tempo.
The range of the Whiskered Screech Owl is almost entirely in Mexico with just a tiny extension into southernmost Arizona where the museum is located.