Bird Gard Pro Sonic Bird Repeller for 1 Acre - Pigeons Comes with one built in speaker and repels birds in a space up to 1 acre. Crystal-Clear Digital Sounds with many Pre-recorded Configurations The built in amplifier and speaker are durable and the unit easily mounts to a fence or post courtesy of the included mounting bracket. Comes with the Pigeon chip. Repel targeted birds from crops, buildings, airports - anywhere birds are a nuisance.