Audio, recorded in Pima County, Arizona (De Anza Trail near Tubac). We could not locate the bird in dense shrubbery and trees.
The bird pips about every 3 seconds. Audio recording 26 seconds in length, on Clyp.It:
https://clyp.it/0ccelkxu?token=086dc0abe7d726932769e00e84c254af