Riddex Silent Bird Repeller - Banish Birds & Eliminate Mess - 900 Sq Ft Riddex emits a powerful ltrasonic sound that only birds can hear, chasing them away Virtually unnoticeable Mounts anywhere and features a dawn to dusk sensor, volume control, automatic & manual frequency and range control up to 16 ft. Uses 6 AA batteries (not included) or AC Adapter (included) Weather resistant. 6"L x 4 1/2"W x 3 1/4"D