Nihao&reg; Eco-friendly Outdoor PIR Sensor and Ultrasonic Bird Repeller Black The product uses PIR Sensor and ultrasonic sound technology which is a humanistic way to expel unwelcome birds. It can be use at garden, farm, balcony, and other outdoors environment. Sound and flashing light repel birds. Non-lethal and non-chemical to human being. Day time and night time working modes are optional.