Abstract: A hazard warning device for night-migrating birds is provided which warns the birds of the presence of a fixed structure or obstacle, e.g., a building or communications tower, against which the birds could collide during night-migration. The device includes a speaker affixed to the structure and a recorder connected to the speaker for, when activated, supplying to the speaker, for continuous broadcast thereby, an infrasonic signal which naturally causes the birds to avoid the structure. In one embodiment, the signal has a frequency close to that of a natural topographic feature and causes the birds to avoid the structure based on the workings of the innate navigational system of the birds. In another embodiment, the recorder supplies a signal which reproduces or mimics the sound of thunder and/or the sound of a lightning strike.

Abstract: A hazard warning device for night-migrating birds is provided which warns the birds of the presence of a fixed structure or obstacle, e.g., a building or communications tower, against which the birds could collide during night-migration. The device includes a speaker affixed to the structure and a recorder connected to the speaker for, when activated, supplying to the speaker, for continuous broadcast thereby, an infrasonic signal which naturally causes the birds to avoid the structure. In one embodiment, the signal has a frequency close to that of a natural topographic feature and causes the birds to avoid the structure based on the workings of the innate navigational system of the birds. In another embodiment, the recorder supplies a signal which reproduces or mimics the sound of thunder and/or the sound of a lightning strike.